feat: migrate to plugins.v1 with filters & actions

This is a very large refactoring which aims at making Tutor both more
extendable and more generic. Historically, the Tutor plugin system was
designed as an ad-hoc solution to allow developers to modify their own
Open edX platforms without having to fork Tutor. The plugin API was
simple, but limited, because of its ad-hoc nature. As a consequence,
there were many things that plugin developers could not do, such as
extending different parts of the CLI or adding custom template filters.

Here, we refactor the whole codebase to make use of a generic plugin
system. This system was inspired by the Wordpress plugin API and the
Open edX "hooks and filters" API. The various components are added to a
small core thanks to a set of actions and filters. Actions are callback
functions that can be triggered at different points of the application
lifecycle. Filters are functions that modify some data. Both actions and
filters are collectively named as "hooks". Hooks can optionally be
created within a certain context, which makes it easier to keep track of
which application created which callback.

This new hooks system allows us to provide a Python API that developers
can use to extend their applications. The API reference is added to the
documentation, along with a new plugin development tutorial.

The plugin v0 API remains supported for backward compatibility of
existing plugins.

Done:
- Do not load commands from plugins which are not enabled.
- Load enabled plugins once on start.
- Implement contexts for actions and filters, which allow us to keep track of
  the source of every hook.
- Migrate patches
- Migrate commands
- Migrate plugin detection
- Migrate templates_root
- Migrate config
- Migrate template environment globals and filters
- Migrate hooks to tasks
- Generate hook documentation
- Generate patch reference documentation
- Add the concept of action priority

Close #499.

CHANGELOG.md

@@ -4,6 +4,8 @@ Note: Breaking changes between versions are indicated by "💥".
 
 ## Unreleased
 
+- 💥[Improvement] Complete overhaul of the plugin extension mechanism. Tutor now has a hook-based Python API: actions can be triggered at different points of the application life cycle and data can be modified thanks to custom filters. The v0 plugin API is still supported, for backward compatibility, but plugin developers are encouraged to migrate their plugins to the new API. See the new plugin tutorial for more information.
+- [Improvement] Improved the output of `tutor plugins list`.
 - [Feature] Add `tutor [dev|local|k8s] status` command, which provides basic information about the platform's status.
 - 💥[Improvement] Make it possible to run `tutor k8s exec <command with multiple arguments>` (#636). As a consequence, it is no longer possible to run quoted commands: `tutor k8s exec "<some command>"`. Instead, you should remove the quotes: `tutor k8s exec <some command>`.
 

Makefile

@@ -28,17 +28,19 @@ push-pythonpackage: ## Push python package to pypi
 
 test: test-lint test-unit test-types test-format test-pythonpackage ## Run all tests by decreasing order of priority
 
+test-static: test-lint test-types test-format  ## Run only static tests
+
 test-format: ## Run code formatting tests
 	black --check --diff $(BLACK_OPTS)
 
 test-lint: ## Run code linting tests
-	pylint --errors-only --enable=unused-import,unused-argument --ignore=templates ${SRC_DIRS}
+	pylint --errors-only --enable=unused-import,unused-argument --ignore=templates --ignore=docs/_ext ${SRC_DIRS}
 
 test-unit: ## Run unit tests
 	python -m unittest discover tests
 
 test-types: ## Check type definitions
-	mypy --exclude=templates --ignore-missing-imports --strict tutor/ tests/
+	mypy --exclude=templates --ignore-missing-imports --strict ${SRC_DIRS}
 
 test-pythonpackage: build-pythonpackage ## Test that package can be uploaded to pypi
 	twine check dist/tutor-$(shell make version).tar.gz
@@ -49,6 +51,9 @@ test-k8s: ## Validate the k8s format with kubectl. Not part of the standard test
 format: ## Format code automatically
 	black $(BLACK_OPTS)
 
+isort: ##  Sort imports. This target is not mandatory because the output may be incompatible with black formatting. Provided for convenience purposes.
+	isort --skip=templates ${SRC_DIRS}
+
 bootstrap-dev: ## Install dev requirements
 	pip install .
 	pip install -r requirements/dev.txt

bin/main.py

@@ -1,25 +1,17 @@
 #!/usr/bin/env python3
-from tutor.plugins import OfficialPlugin
+from tutor import hooks
 from tutor.commands.cli import main
+from tutor.plugins.v0 import OfficialPlugin
+
+
+@hooks.Actions.CORE_READY.add()
+def _discover_official_plugins() -> None:
+    # Manually discover plugins: that's because entrypoint plugins are not properly
+    # detected within the binary bundle.
+    with hooks.Contexts.PLUGINS.enter():
+        OfficialPlugin.discover_all()
 
-# Manually install plugins (this is for creating the bundle)
-for plugin_name in [
-    "android",
-    "discovery",
-    "ecommerce",
-    "forum",
-    "license",
-    "mfe",
-    "minio",
-    "notes",
-    "richie",
-    "webui",
-    "xqueue",
-]:
-    try:
-        OfficialPlugin.load(plugin_name)
-    except ImportError:
-        pass
 
 if __name__ == "__main__":
+    # Call the regular main function, which will not detect any entrypoint plugin
     main()

docs/Makefile

@@ -11,4 +11,7 @@ browse:
 	sensible-browser _build/html/index.html
 
 watch: build browse
-	while true; do inotifywait -e modify *.rst */*.rst */*/*.rst ../*.rst conf.py; $(MAKE) build || true; done
+	while true; do $(MAKE) wait-for-change build || true; done
+
+wait-for-change:
+	inotifywait -e modify $(shell find . -name "*.rst") ../*.rst ../tutor/hooks/*.py conf.py

docs/_ext/tutordocs.py

@@ -0,0 +1,14 @@
+"""
+This module is heavily inspired by Django's djangodocs.py:
+https://github.com/django/django/blob/main/docs/_ext/djangodocs.py
+"""
+from sphinx.application import Sphinx
+
+
+def setup(app: Sphinx) -> None:
+    # https://www.sphinx-doc.org/en/master/extdev/appapi.html#sphinx.application.Sphinx.add_crossref_type
+    app.add_crossref_type(
+        directivename="patch",
+        rolename="patch",
+        indextemplate="pair: %s; patch",
+    )

docs/conf.py

@@ -27,6 +27,10 @@ language = None
 exclude_patterns = ["_build", "Thumbs.db", ".DS_Store"]
 pygments_style = None
 
+# Autodocumentation of modules
+extensions.append("sphinx.ext.autodoc")
+autodoc_typehints = "description"
+
 # -- Sphinx-Click configuration
 # https://sphinx-click.readthedocs.io/
 extensions.append("sphinx_click")
@@ -108,5 +112,10 @@ def youtube(
     ]
 
 
-youtube.content = True
-docutils.parsers.rst.directives.register_directive("youtube", youtube)
+# Tutor's own extension
+sys.path.append(os.path.join(os.path.dirname(__file__), "_ext"))
+extensions.append("tutordocs")
+
+
+setattr(youtube, "content", True)
+docutils.parsers.rst.directives.register_directive("youtube", youtube)  # type: ignore

docs/index.rst

@@ -22,9 +22,9 @@
    gettingstarted
    run
    configuration
-   plugins
-   reference
-   tutorials
+   plugins/index
+   reference/index
+   tutorials/index
    troubleshooting
    tutor
    faq
@@ -59,6 +59,6 @@ This work is licensed under the terms of the `GNU Affero General Public License
 
 The AGPL license covers the Tutor code, including the Dockerfiles, but not the content of the Docker images which can be downloaded from https://hub.docker.com. Software other than Tutor provided with the docker images retain their original license.
 
-The Tutor plugin system is licensed under the terms of the `Apache License, Version 2.0 <https://opensource.org/licenses/Apache-2.0>`__.
+The Tutor plugin and hooks system is licensed under the terms of the `Apache License, Version 2.0 <https://opensource.org/licenses/Apache-2.0>`__.
 
 © 2021 Tutor is a registered trademark of SASU NULI NULI. All Rights Reserved.

docs/intro.rst

@@ -70,6 +70,8 @@ Urls:
 
 The platform is reset every day at 9:00 AM, `Paris (France) time <https://time.is/Paris>`__, so feel free to try and break things as much as you want.
 
+.. _how_does_tutor_work:
+
 How does Tutor work?
 --------------------
 

docs/plugins/examples.rst

@@ -1,62 +1,87 @@
 .. _plugins_examples:
 
-Examples of Tutor plugins
-=========================
+========
+Examples
+========
 
 The following are simple examples of :ref:`Tutor plugins <plugins>` that can be used to modify the behaviour of Open edX.
 
 Skip email validation for new users
------------------------------------
+===================================
 
 ::
 
-    name: skipemailvalidation
-    version: 0.1.0
-    patches:
-      common-env-features: |
-        "SKIP_EMAIL_VALIDATION": true
+    from tutor import hooks
+
+    hooks.Filters.ENV_PATCHES.add_item(
+        (
+            "common-env-features",
+            """
+    "SKIP_EMAIL_VALIDATION": true
+    """"
+        )
+    )
 
 Enable bulk enrollment view in the LMS
---------------------------------------
+======================================
 
 ::
 
-    name: enablebulkenrollmentview
-    version: 0.1.0
-    patches:
-      lms-env-features: |
-        "ENABLE_BULK_ENROLLMENT_VIEW": true
+    from tutor import hooks
+
+    hooks.Filters.ENV_PATCHES.add_item(
+        (
+            "lms-env-features",
+            """
+    "ENABLE_BULK_ENROLLMENT_VIEW": true
+    """
+        )
+    )
 
 Enable Google Analytics
------------------------
+=======================
 
 ::
 
-    name: googleanalytics
-    version: 0.1.0
-    patches:
-      openedx-common-settings: |
-        # googleanalytics special settings
-        GOOGLE_ANALYTICS_ACCOUNT = "UA-your-account"
-        GOOGLE_ANALYTICS_TRACKING_ID = "UA-your-tracking-id"
+    from tutor import hooks
+
+    hooks.Filters.ENV_PATCHES.add_item(
+        (
+            "openedx-common-settings",
+            """
+  # googleanalytics special settings
+  GOOGLE_ANALYTICS_ACCOUNT = "UA-your-account"
+  GOOGLE_ANALYTICS_TRACKING_ID = "UA-your-tracking-id"
+  """
+        )
+    )
 
 Enable SAML authentication
---------------------------
+==========================
 
 ::
 
-    name: saml
-    version: 0.1.0
-    patches:
-      common-env-features: |
-        "ENABLE_THIRD_PARTY_AUTH": true
+    from tutor import hooks
 
-      openedx-lms-common-settings: |
-        # saml special settings
-        AUTHENTICATION_BACKENDS += ["common.djangoapps.third_party_auth.saml.SAMLAuthBackend", "django.contrib.auth.backends.ModelBackend"]
-
-      openedx-auth: |
-        "SOCIAL_AUTH_SAML_SP_PRIVATE_KEY": "yoursecretkey",
-        "SOCIAL_AUTH_SAML_SP_PUBLIC_CERT": "yourpubliccert"
+    hooks.Filters.ENV_PATCHES.add_items([
+        (
+            "common-env-features",
+            '"ENABLE_THIRD_PARTY_AUTH": true',
+        ),
+        (
+            "openedx-lms-common-settings:",
+            """
+    # saml special settings
+    AUTHENTICATION_BACKENDS += ["common.djangoapps.third_party_auth.saml.SAMLAuthBackend", "django.contrib.auth.backends.ModelBackend"]
+    """
+        ),
+        (
+            "openedx-auth",
+            """
+    "SOCIAL_AUTH_SAML_SP_PRIVATE_KEY": "yoursecretkey",
+    "SOCIAL_AUTH_SAML_SP_PUBLIC_CERT": "yourpubliccert"
+            """
+        ),
+    ])
 
 Do not forget to replace "yoursecretkey" and "yourpubliccert" with your own values.

docs/plugins/index.rst

@@ -0,0 +1,11 @@
+
+=======
+Plugins
+=======
+
+.. toctree::
+   :maxdepth: 2
+
+   intro
+   examples
+   v0/index

docs/plugins/intro.rst

@@ -1,7 +1,8 @@
 .. _plugins:
 
-Plugins
-=======
+============
+Introduction
+============
 
 Tutor comes with a plugin system that allows anyone to customise the deployment of an Open edX platform very easily. The vision behind this plugin system is that users should not have to fork the Tutor repository to customise their deployments. For instance, if you have created a new application that integrates with Open edX, you should not have to describe how to manually patch the platform settings, ``urls.py`` or ``*.env.json`` files. Instead, you can create a "tutor-myapp" plugin for Tutor. Then, users will start using your application in three simple steps::
 
@@ -12,12 +13,10 @@ Tutor comes with a plugin system that allows anyone to customise the deployment
     # 3) Reconfigure and restart the platform
     tutor local quickstart
 
-For simple changes, it may be extremely easy to create a Tutor plugin: even non-technical users may get started with :ref:`simple YAML plugins <plugins_yaml>`.
+For simple changes, it may be extremely easy to create a Tutor plugin: even non-technical users may get started with our :ref:`plugin_development_tutorial` tutorial. We also provide a list of :ref:`simple example plugins <plugins_examples>`.
 
-In the following, we learn how to use and create Tutor plugins.
-
-Commands
---------
+Plugin commands cheatsheet
+==========================
 
 List installed plugins::
 
@@ -32,19 +31,11 @@ After enabling or disabling a plugin, the environment should be re-generated wit
 
     tutor config save
 
+The full plugins CLI is described in the :ref:`reference documentation <cli_plugins>`.
+
 .. _existing_plugins:
 
 Existing plugins
-----------------
+================
 
 Officially-supported plugins are listed on the `Overhang.IO <https://overhang.io/tutor/plugins>`__ website.
-
-Plugin development
-------------------
-
-.. toctree::
-   :maxdepth: 2
-
-   plugins/api
-   plugins/gettingstarted
-   plugins/examples

docs/plugins/v0/api.rst

@@ -1,22 +1,24 @@
 Plugin API
 ==========
 
+.. include:: legacy.rst
+
 Plugins can affect the behaviour of Tutor at multiple levels. They can:
 
-* Add new settings or modify existing ones in the Tutor configuration (see :ref:`config <plugin_config>`).
-* Add new templates to the Tutor project environment or modify existing ones (see :ref:`patches <plugin_patches>`, :ref:`templates <plugin_templates>` and :ref:`hooks <plugin_hooks>`).
-* Add custom commands to the Tutor CLI (see :ref:`command <plugin_command>`).
+* Add new settings or modify existing ones in the Tutor configuration (see :ref:`config <v0_plugin_config>`).
+* Add new templates to the Tutor project environment or modify existing ones (see :ref:`patches <v0_plugin_patches>`, :ref:`templates <v0_plugin_templates>` and :ref:`hooks <v0_plugin_hooks>`).
+* Add custom commands to the Tutor CLI (see :ref:`command <v0_plugin_command>`).
 
 There exist two different APIs to create Tutor plugins: either with YAML files or Python packages. YAML files are more simple to create but are limited to just configuration and template patches.
 
-.. _plugin_config:
+.. _v0_plugin_config:
 
 config
 ~~~~~~
 
 The ``config`` attribute is used to modify existing and add new configuration parameters:
 
-* ``config["add"]`` are key/values that should be added to the user-specific ``config.yml`` configuration. Add their passwords, secret keys, and other values that do not have a default value.
+* ``config["add"]`` are key/values that should be added to the user-specific ``config.yml`` configuration. Add there the passwords, secret keys, and other values that do not have a reasonable default value for all users.
 * ``config["defaults"]`` are default key/values for this plugin. These values can be accessed even though they are not added to the ``config.yml`` user file. Users can override them manually with ``tutor config save --set ...``.
 * ``config["set"]`` are existing key/values that should be modified. Be very careful what you add there! Different plugins may define conflicting values for some parameters.
 
@@ -42,19 +44,12 @@ This configuration from the "myplugin" plugin will set the following values:
 - ``MYPLUGIN_DOCKER_IMAGE``: this value will by default not be stored in ``config.yml``, but ``tutor config printvalue MYPLUGIN_DOCKER_IMAGE`` will print ``username/imagename:latest``.
 - ``MASTER_PASSWORD`` will be set to ``h4cked``. Needless to say, plugin developers should avoid doing this.
 
-.. _plugin_patches:
+.. _v0_plugin_patches:
 
 patches
 ~~~~~~~
 
-Plugin patches affect the rendered environment templates. In many places the Tutor templates include calls to ``{{ patch("patchname") }}``. This grants plugin developers the possibility to modify the content of rendered templates. Plugins can add content in these places by adding values to the ``patches`` attribute.
-
-.. note::
-    The list of existing patches can be found by searching for `{{ patch(` strings in the Tutor source code::
-
-        git grep "{{ patch"
-
-    The list of patches can also be browsed online `on Github <https://github.com/search?utf8=✓&q={{+patch+repo%3Aoverhangio%2Ftutor+path%3A%2Ftutor%2Ftemplates&type=Code&ref=advsearch&l=&l= 8>`__.
+Plugin patches affect the rendered environment templates. In many places the Tutor templates include calls to ``{{ patch("patchname") }}``. This grants plugin developers the possibility to modify the content of rendered templates. Plugins can add content in these places by adding values to the ``patches`` attribute. See :ref:`patches` for the complete list available patches.
 
 Example::
 
@@ -70,7 +65,7 @@ This will add a Redis instance to the services run with ``tutor local`` commands
     One can use this to dynamically load a list of patch files from a folder.
 
 
-.. _plugin_hooks:
+.. _v0_plugin_hooks:
 
 hooks
 ~~~~~
@@ -141,7 +136,7 @@ or::
     tutor images pull all
     tutor images push all
 
-.. _plugin_templates:
+.. _v0_plugin_templates:
 
 templates
 ~~~~~~~~~
@@ -162,7 +157,7 @@ In Tutor, templates are `Jinja2 <https://jinja.palletsprojects.com/en/2.11.x/>`_
 * ``list_if``: In a list of ``(value, condition)`` tuples, return the list of ``value`` for which the ``condition`` is true.
 * ``long_to_base64``: Base-64 encode a long integer.
 * ``iter_values_named``: Yield the values of the configuration settings that match a certain pattern. Example: ``{% for value in iter_values_named(prefix="KEY", suffix="SUFFIX")%}...{% endfor %}``. By default, only non-empty values are yielded. To iterate also on empty values, pass the ``allow_empty=True`` argument.
-* ``patch``: See :ref:`patches <plugin_patches>`.
+* ``patch``: See :ref:`patches <v0_plugin_patches>`.
 * ``random_string``: Return a random string of the given length composed of ASCII letters and digits. Example: ``{{ 8|random_string }}``.
 * ``reverse_host``: Reverse a domain name (see `reference <https://en.wikipedia.org/wiki/Reverse_domain_name_notation>`__). Example: ``{{ "demo.myopenedx.com"|reverse_host }}`` is equal to "com.myopenedx.demo".
 * ``rsa_import_key``: Import a PEM-formatted RSA key and return the corresponding object.
@@ -178,7 +173,7 @@ When saving the environment, template files that are stored in a template root w
 * Binary files with the following extensions: .ico, .jpg, .png, .ttf
 * Files that are stored in a folder named "partials", or one of its subfolders.
 
-.. _plugin_command:
+.. _v0_plugin_command:
 
 command
 ~~~~~~~

docs/plugins/v0/gettingstarted.rst

@@ -1,6 +1,8 @@
 Getting started with plugin development
 =======================================
 
+.. include:: legacy.rst
+
 Plugins can be created in two different ways: either as plain YAML files or installable Python packages. YAML files are great when you need to make minor changes to the default platform, such as modifying settings. For creating more complex applications, it is recommended to create python packages.
 
 .. _plugins_yaml:

docs/plugins/v0/index.rst

@@ -0,0 +1,11 @@
+=============
+Legacy v0 API
+=============
+
+.. include:: legacy.rst
+
+.. toctree::
+   :maxdepth: 2
+
+   api
+   gettingstarted

docs/plugins/v0/legacy.rst

@@ -0,0 +1 @@
+.. warning:: The v0 plugin API is no longer the recommended way of developing new plugins for Tutor, starting from Tutor v13.2.0. See our :ref:`plugin creation tutorial <plugin_development_tutorial>` to learn more about the v1 plugin API. Existing v0 plugins will remain supported for some time but developers are encouraged to start migrating their plugins as soon as possible to make use of the new API. Please read the `upgrade instructions <https://github.com/overhangio/cookiecutter-tutor-plugin>`__ to upgrade v0 plugins generated with the v0 plugin cookiecutter.

docs/reference.rst

@@ -1,13 +0,0 @@
-CLI Reference
-=============
-
-.. toctree::
-   :maxdepth: 2
-
-   reference/cli/tutor
-   reference/cli/config
-   reference/cli/dev
-   reference/cli/images
-   reference/cli/k8s
-   reference/cli/local
-   reference/cli/plugins

docs/reference/api/hooks/actions.rst

@@ -0,0 +1,17 @@
+.. _actions:
+
+=======
+Actions
+=======
+
+Actions are one of the two types of hooks (the other being :ref:`filters`) that can be used to extend Tutor. Each action represents an event that can occur during the application life cycle. Each action has a name, and callback functions can be attached to it. When an action is triggered, these callback functions are called in sequence. Each callback function can trigger side effects, independently from one another.
+
+.. autofunction:: tutor.hooks.actions::get
+.. autofunction:: tutor.hooks.actions::get_template
+.. autofunction:: tutor.hooks.actions::add
+.. autofunction:: tutor.hooks.actions::do
+.. autofunction:: tutor.hooks.actions::clear
+.. autofunction:: tutor.hooks.actions::clear_all
+
+.. autoclass:: tutor.hooks.actions.Action
+.. autoclass:: tutor.hooks.actions.ActionTemplate

docs/reference/api/hooks/consts.rst

@@ -0,0 +1,23 @@
+=========
+Constants
+=========
+
+Here we lists named :ref:`actions`, :ref:`filters` and :ref:`contexts` that are used across Tutor. These are simply hook variables that we can refer to across the Tutor codebase without having to hard-code string names. The API is slightly different and less verbose than "native" hooks.
+
+Actions
+=======
+
+.. autoclass:: tutor.hooks.Actions
+    :members:
+
+Filters
+=======
+
+.. autoclass:: tutor.hooks.Filters
+    :members:
+
+Contexts
+========
+
+.. autoclass:: tutor.hooks.Contexts
+    :members:

docs/reference/api/hooks/contexts.rst

@@ -0,0 +1,11 @@
+.. _contexts:
+
+========
+Contexts
+========
+
+Contexts are a feature of the hook-based extension system in Tutor, which allows us to keep track of which components of the code created which callbacks. Contexts are very much an internal concept that most plugin developers should not have to worry about.
+
+.. autofunction:: tutor.hooks.contexts::enter
+
+.. autoclass:: tutor.hooks.contexts.Context

docs/reference/api/hooks/filters.rst

@@ -0,0 +1,20 @@
+.. _filters:
+
+=======
+Filters
+=======
+
+Filters are one of the two types of hooks (the other being :ref:`actions`) that can be used to extend Tutor. Filters allow one to modify the application behavior by transforming data. Each filter has a name, and callback functions can be attached to it. When a filter is applied, these callback functions are called in sequence; the result of each callback function is passed as the first argument to the next callback function. The result of the final callback function is returned to the application as the filter's output.
+
+.. autofunction:: tutor.hooks.filters::get
+.. autofunction:: tutor.hooks.filters::get_template
+.. autofunction:: tutor.hooks.filters::add
+.. autofunction:: tutor.hooks.filters::add_item
+.. autofunction:: tutor.hooks.filters::add_items
+.. autofunction:: tutor.hooks.filters::apply
+.. autofunction:: tutor.hooks.filters::iterate
+.. autofunction:: tutor.hooks.filters::clear
+.. autofunction:: tutor.hooks.filters::clear_all
+
+.. autoclass:: tutor.hooks.filters.Filter
+.. autoclass:: tutor.hooks.filters.FilterTemplate

docs/reference/api/hooks/index.rst

@@ -0,0 +1,11 @@
+=========
+Hooks API
+=========
+
+.. toctree::
+   :maxdepth: 1
+
+   actions
+   filters
+   contexts
+   consts

docs/reference/cli/index.rst

@@ -0,0 +1,13 @@
+Command line interface (CLI)
+============================
+
+.. toctree::
+   :maxdepth: 2
+
+   tutor
+   config
+   dev
+   images
+   k8s
+   local
+   plugins

docs/reference/cli/plugins.rst

@@ -1,3 +1,5 @@
+.. _cli_plugins:
+
 .. click:: tutor.commands.plugins:plugins_command
    :prog: tutor plugins
    :nested: full

docs/reference/index.rst

@@ -0,0 +1,9 @@
+Reference
+=========
+
+.. toctree::
+   :maxdepth: 2
+
+   api/hooks/index
+   cli/index
+   patches

docs/reference/patches.rst

@@ -0,0 +1,329 @@
+.. _patches:
+
+================
+Template patches
+================
+
+This is the list of all patches used across Tutor (outside of any plugin). Alternatively, you can search for patches in Tutor templates by grepping the source code::
+
+    git clone https://github.com/overhangio/tutor
+    cd tutor
+    git grep "{{ patch" -- tutor/templates
+
+See also `this GitHub search <https://github.com/search?utf8=✓&q={{+patch+repo%3Aoverhangio%2Ftutor+path%3A%2Ftutor%2Ftemplates&type=Code&ref=advsearch&l=&l= 8>`__.
+
+.. patch:: caddyfile
+
+``caddyfile``
+=============
+
+File: ``apps/caddy/Caddyfile``
+
+Add here Caddy directives to redirect traffic from the outside to your service containers. You should make use of the "proxy" snippet that simplifies configuration and automatically configures logging. Also, make sure to use the ``$default_site_port`` environment variable to make sure that your service will be accessible both when HTTPS is enabled or disabled. For instance::
+
+    {{ MYPLUGIN_HOST }}{$default_site_port} {
+        import proxy "myservice:8000"
+    }
+
+See the `Caddy reference documentation <https://caddyserver.com/docs/caddyfile>`__ for more information.
+
+.. patch:: caddyfile-cms
+
+``caddyfile-cms``
+=================
+
+File: ``apps/caddy/Caddyfile``
+
+.. patch:: caddyfile-global
+
+``caddyfile-global``
+====================
+
+File: ``apps/caddy/Caddyfile``
+
+.. patch:: caddyfile-lms
+
+``caddyfile-lms``
+=================
+
+File: ``apps/caddy/Caddyfile``
+
+.. patch:: cms-env
+
+``cms-env``
+===========
+
+File: ``apps/openedx/config/cms.env.json``
+
+.. patch:: cms-env-features
+
+``cms-env-features``
+====================
+
+File: ``apps/openedx/config/cms.env.json``
+
+.. patch:: common-env-features
+
+``common-env-features``
+=======================
+
+Files: ``apps/openedx/config/cms.env.json``, ``apps/openedx/config/lms.env.json``
+
+.. patch:: dev-docker-compose-jobs-services
+
+``dev-docker-compose-jobs-services``
+====================================
+
+File: ``dev/docker-compose.jobs.yml``
+
+.. patch:: k8s-deployments
+
+``k8s-deployments``
+===================
+
+File: ``k8s/deployments.yml``
+
+.. patch:: k8s-jobs
+
+``k8s-jobs``
+============
+
+File: ``k8s/jobs.yml``
+
+.. patch:: k8s-services
+
+``k8s-services``
+================
+
+File: ``k8s/services.yml``
+
+.. patch:: k8s-volumes
+
+``k8s-volumes``
+===============
+
+File: ``k8s/volumes.yml``
+
+.. patch:: kustomization
+
+``kustomization``
+=================
+
+File: ``kustomization.yml``
+
+.. patch:: kustomization-commonlabels
+
+``kustomization-commonlabels``
+==============================
+
+File: ``kustomization.yml``
+
+.. patch:: kustomization-configmapgenerator
+
+``kustomization-configmapgenerator``
+====================================
+
+File: ``kustomization.yml``
+
+.. patch:: kustomization-resources
+
+``kustomization-resources``
+===========================
+
+File: ``kustomization.yml``
+
+.. patch:: lms-env
+
+``lms-env``
+===========
+
+File: ``apps/openedx/config/lms.env.json``
+
+.. patch:: lms-env-features
+
+``lms-env-features``
+====================
+
+File: ``apps/openedx/config/lms.env.json``
+
+.. patch:: local-docker-compose-caddy-aliases
+
+``local-docker-compose-caddy-aliases``
+======================================
+
+File: ``local/docker-compose.prod.yml``
+
+.. patch:: local-docker-compose-cms-dependencies
+
+``local-docker-compose-cms-dependencies``
+=========================================
+
+File: ``local/docker-compose.yml``
+
+.. patch:: local-docker-compose-dev-services
+
+``local-docker-compose-dev-services``
+=====================================
+
+File: ``dev/docker-compose.yml``
+
+.. patch:: local-docker-compose-jobs-services
+
+``local-docker-compose-jobs-services``
+======================================
+
+File: ``local/docker-compose.jobs.yml``
+
+.. patch:: local-docker-compose-lms-dependencies
+
+``local-docker-compose-lms-dependencies``
+=========================================
+
+File: ``local/docker-compose.yml``
+
+.. patch:: local-docker-compose-prod-services
+
+``local-docker-compose-prod-services``
+======================================
+
+File: ``local/docker-compose.prod.yml``
+
+.. patch:: local-docker-compose-services
+
+``local-docker-compose-services``
+=================================
+
+File: ``local/docker-compose.yml``
+
+.. patch:: openedx-auth
+
+``openedx-auth``
+================
+
+File: ``apps/openedx/config/partials/auth.json``
+
+.. patch:: openedx-cms-common-settings
+
+``openedx-cms-common-settings``
+===============================
+
+File: ``apps/openedx/settings/partials/common_cms.py``
+
+.. patch:: openedx-cms-development-settings
+
+``openedx-cms-development-settings``
+====================================
+
+File: ``apps/openedx/settings/cms/development.py``
+
+.. patch:: openedx-cms-production-settings
+
+``openedx-cms-production-settings``
+===================================
+
+File: ``apps/openedx/settings/cms/production.py``
+
+.. patch:: openedx-common-assets-settings
+
+``openedx-common-assets-settings``
+==================================
+
+File: ``build/openedx/settings/partials/assets.py``
+
+
+.. patch:: openedx-common-i18n-settings
+
+``openedx-common-i18n-settings``
+================================
+
+File: ``build/openedx/settings/partials/i18n.py``
+
+.. patch:: openedx-common-settings
+
+``openedx-common-settings``
+===========================
+
+File: ``apps/openedx/settings/partials/common_all.py``
+
+.. patch:: openedx-dev-dockerfile-post-python-requirements
+
+``openedx-dev-dockerfile-post-python-requirements``
+===================================================
+
+File: ``build/openedx/Dockerfile``
+
+.. patch:: openedx-development-settings
+
+``openedx-development-settings``
+================================
+
+Files: ``apps/openedx/settings/cms/development.py``, ``apps/openedx/settings/lms/development.py``
+
+.. patch:: openedx-dockerfile
+
+``openedx-dockerfile``
+======================
+
+File: ``build/openedx/Dockerfile``
+
+.. patch:: openedx-dockerfile-git-patches-default
+
+``openedx-dockerfile-git-patches-default``
+==========================================
+
+File: ``build/openedx/Dockerfile``
+
+.. patch:: openedx-dockerfile-minimal
+
+``openedx-dockerfile-minimal``
+==============================
+
+File: ``build/openedx/Dockerfile``
+
+.. patch:: openedx-dockerfile-post-git-checkout
+
+``openedx-dockerfile-post-git-checkout``
+========================================
+
+File: ``build/openedx/Dockerfile``
+
+.. patch:: openedx-dockerfile-post-python-requirements
+
+``openedx-dockerfile-post-python-requirements``
+===============================================
+
+File: ``build/openedx/Dockerfile``
+
+.. patch:: openedx-dockerfile-pre-assets
+
+``openedx-dockerfile-pre-assets``
+=================================
+
+File: ``build/openedx/Dockerfile``
+
+.. patch:: openedx-lms-common-settings
+
+``openedx-lms-common-settings``
+===============================
+
+File: ``apps/openedx/settings/partials/common_lms.py``
+
+Python-formatted LMS settings used both in production and development.
+
+.. patch:: openedx-lms-development-settings
+
+``openedx-lms-development-settings``
+====================================
+
+File: ``apps/openedx/settings/lms/development.py``
+
+Python-formatted LMS settings in development. Values defined here override the values from :patch:`openedx-lms-common-settings` or :patch:`openedx-lms-production-settings`.
+
+.. patch:: openedx-lms-production-settings
+
+``openedx-lms-production-settings``
+===================================
+
+File: ``apps/openedx/settings/lms/production.py``
+
+Python-formatted LMS settings in production. Values defined here override the values from :patch:`openedx-lms-common-settings`.

docs/tutorials.rst

@@ -1,30 +0,0 @@
-Tutorials
-=========
-
-Open edX customization
-----------------------
-
-.. toctree::
-   :maxdepth: 2
-
-   tutorials/theming
-   tutorials/edx-platform-settings
-   tutorials/google-smtp
-   tutorials/nightly
-
-System administration
----------------------
-
-.. toctree::
-   :maxdepth: 2
-
-   tutorials/scale
-   tutorials/portainer
-   tutorials/podman
-   tutorials/proxy
-   tutorials/datamigration
-   tutorials/multiplatforms
-   tutorials/oldreleases
-   tutorials/arm64
-
-Other tutorials can be found in the official Tutor forums, `in the "Tutorials" category <https://discuss.overhang.io/c/tutor/tutorials/13>`__.

docs/tutorials/index.rst

@@ -0,0 +1,31 @@
+Tutorials
+=========
+
+Open edX customization
+----------------------
+
+.. toctree::
+   :maxdepth: 1
+
+   plugin
+   theming
+   edx-platform-settings
+   google-smtp
+   nightly
+
+System administration
+---------------------
+
+.. toctree::
+   :maxdepth: 1
+
+   scale
+   portainer
+   podman
+   proxy
+   datamigration
+   multiplatforms
+   oldreleases
+   arm64
+
+Other tutorials can be found in the official Tutor forums, `in the "Tutorials" category <https://discuss.overhang.io/c/tutor/tutorials/13>`__.

docs/tutorials/plugin.rst

@@ -0,0 +1,354 @@
+.. _plugin_development_tutorial:
+
+=======================
+Creating a Tutor plugin
+=======================
+
+Tutor plugins are the offically recommended way of customizing the behaviour of Tutor. If Tutor does not do things the way you want, then your first reaction should *not* be to fork Tutor, but instead to figure out whether you can create a plugin that will allow you to achieve what you want.
+
+You may be thinking that creating a plugin might be overkill for your use case. It's almost certainly not! The stable plugin API guarantees that your changes will keep working even after you upgrade from one major release to the next, with little to no extra work. Also, it allows you to distribute your changes to other users.
+
+A plugin can be created either as a simple, single Python module (a ``*.py`` file) or as a full-blown Python package. Single Python modules are easier to write, while Python packages can be distributed more easily with ``pip install ...``. We'll start by writing our plugin as a single Python module.
+
+Writing a plugin as a single Python module
+==========================================
+
+Getting started
+---------------
+
+In the following, we'll create a new plugin called "myplugin". We start by creating the plugins root folder::
+
+    $ mkdir -p "$(tutor plugins printroot)"
+
+Then, create an empty "myplugin.py" file in this folder::
+
+    $ touch "$(tutor plugins printroot)/myplugin.py"
+
+We can verify that the plugin is correctly detected by running::
+
+    $ tutor plugins list
+    ...
+    myplugin    (disabled)    /home/yourusername/.local/share/tutor-plugins/myplugin.py
+    ...
+
+Our plugin is disabled, for now. To enable it, we run::
+
+    $ tutor plugins enable myplugin
+    Plugin myplugin enabled
+    Configuration saved to /home/yourusername/.local/share/tutor/config.yml
+    You should now re-generate your environment with `tutor config save`.
+
+At this point you could re-generate your environment with ``tutor config save``, but there would not be any change to your environment... because the plugin does not do anything. So let's get started and make some changes.
+
+Modifying existing files with patches
+-------------------------------------
+
+We'll start by modifying some of our Open edX settings files. It's a frequent requirement to modify the ``FEATURES`` setting from the LMS or the CMS in edx-platform. In the legacy native installation, this was done by modifying the ``lms.env.yml`` and ``cms.env.yml`` files. Here we'll modify the Python setting files that define the edx-platform configuration. To achieve that we'll make use of two concepts from the Tutor API: :ref:`patches` and :ref:`filters`.
+
+If you have not already read :ref:`how_does_tutor_work` now would be a good time :-) Tutor uses templates to generate various files, such as settings, Dockerfiles, etc. These templates include ``{{ patch("patch-name") }}`` statements that allow plugins to insert arbitrary content in there. These patches are located at strategic locations. See :ref:`patches` for more information.
+
+Let's say that we would like to limit access to our brand new Open edX platform. It is not ready for prime-time yet, so we want to prevent users from registering new accounts. There is a feature flag for that in the LMS: `FEATURES['ALLOW_PUBLIC_ACCOUNT_CREATION'] <https://edx.readthedocs.io/projects/edx-platform-technical/en/latest/featuretoggles.html#featuretoggle-FEATURES['ALLOW_PUBLIC_ACCOUNT_CREATION']>`__. By default this flag is set to a true value, enabling anyone to create an account. In the following we'll set it to false.
+
+Add the following content to the ``myplugin.py`` file that you created earlier::
+
+    from tutor import hooks
+
+    hooks.Filters.ENV_PATCHES.add_item(
+        (
+            "openedx-lms-common-settings",
+            "FEATURES['ALLOW_PUBLIC_ACCOUNT_CREATION'] = False"
+        )
+    )
+
+Let's go over these changes one by one::
+
+    from tutor import hooks
+
+This imports the ``hooks`` module from Tutor, which grants us access to ``hooks.Actions`` and ``hooks.Filters`` (among other things).
+
+::
+
+    hooks.Filters.ENV_PATCHES.add_item(
+        <name>,
+        <content>
+    )
+
+This means "add ``<content>`` to the ``{{ patch("<name>") }}`` statement, thanks to the  ENV_PATCHES filter". In our case, we want to modify the LMS settings, both in production and development. The right patch for that is :patch:`openedx-lms-common-settings`. We add one item, which is a single Python-formatted line of code::
+
+    "FEATURES['ALLOW_PUBLIC_ACCOUNT_CREATION'] = False"
+
+.. note:: Notice how "False" starts with a capital "F"? That's how booleans are created in Python.
+
+Now, re-render your environment with::
+
+    $ tutor config save
+
+You can check that the feature was added to your environment::
+
+    $ grep -r ALLOW_PUBLIC_ACCOUNT_CREATION "$(tutor config printroot)/env"
+    /home/yourusername/.local/share/tutor/env/apps/openedx/settings/lms/production.py:FEATURES['ALLOW_PUBLIC_ACCOUNT_CREATION'] = False
+    /home/yourusername/.local/share/tutor/env/apps/openedx/settings/lms/development.py:FEATURES['ALLOW_PUBLIC_ACCOUNT_CREATION'] = False
+
+Your new settings will be taken into account by restarting your platform::
+
+    $ tutor local restart
+
+Congratulations! You've created your first working plugin. As you can guess, you can add changes to other files by adding other similar patch statements to your plugin.
+
+Modifying configuration
+-----------------------
+
+In the previous section you've learned how to add custom content to the Tutor templates. Now we'll see how to modify the Tutor configuration. Configuration settings can be specified in three ways:
+
+1. "unique" settings that need to be generated or user-specified, and then preserved in config.yml: such settings do not have reasonable defaults for all users. Examples of such setttings include passwords and secret keys, which should be different for every user.
+2. "default" settings have static fallback values. They are only stored in config.yml when they are modified by users. Most settings belong in this category.
+3. "override" settings modify configuration from Tutor core or from other plugins. These will be removed and restored to their default values when the plugin is disabled.
+
+It is very strongly recommended to prefix unique and default settings with the plugin name, in all-caps, such that different plugins with the same configuration do not conflict with one another.
+
+As an example, we'll make it possible to configure public account creation on the LMS via a Tutor setting. In the previous section we achieved that by creating a patch. Let's modify this patch::
+
+    hooks.Filters.ENV_PATCHES.add_item(
+        (
+            "openedx-lms-common-settings",
+            "FEATURES['ALLOW_PUBLIC_ACCOUNT_CREATION'] = {% if MYPLUGIN_PLATFORM_IS_PUBLIC %}True{% else %}False{% endif %}",
+        )
+    )
+
+This new patch makes use of the ``MYPLUGIN_PLATFORM_IS_PUBLIC`` configuration setting, which we need to create. Since this setting is specific to our plugin and should be stored in config.yml only when it's modified, we create it as a "default" setting. We do that with the :py:data:`tutor.hooks.Filters.CONFIG_DEFAULTS` filter::
+
+    hooks.Filters.CONFIG_DEFAULTS.add_item(
+        ("MYPLUGIN_PLATFORM_IS_PUBLIC", False)
+    )
+
+You can check that the new configuration setting was properly defined::
+
+    $ tutor config printvalue MYPLUGIN_PLATFORM_IS_PUBLIC
+    False
+
+Now you can quickly toggle the public account creation feature by modifying the new setting::
+
+    $ tutor config save --set MYPLUGIN_PLATFORM_IS_PUBLIC=True
+    $ tutor local restart
+
+
+Adding new templates
+--------------------
+
+If you are adding an extra application to your Open edX platform, there is a good chance that you will create a new Docker image with a custom Dockerfile. This new application will have its own settings and build assets, for instance. This means that you need to add new templates to the Tutor environment. To do that, we will create a new subfolder in our plugins folder::
+
+    $ mkdir -p "$(tutor plugins printroot)/templates/myplugin"
+
+Then we tell Tutor about this new template root thanks to the :py:data:`tutor.hooks.Filters.ENV_TEMPLATE_ROOTS` filter::
+
+    import os
+
+    template_folder = os.path.join(os.path.dirname(__file__), "templates")
+    hooks.Filters.ENV_TEMPLATE_ROOTS.add_item(template_folder)
+
+We create a "build" subfolder which will contain all assets to build our "myservice" image::
+
+    $ mkdir -p "$(tutor plugins printroot)/templates/myplugin/build/myservice"
+
+Create the following Dockerfile in ``$(tutor plugins printroot)/templates/myplugin/build/myservice/Dockerfile``::
+
+    FROM docker.io/debian:bullseye-slim
+    CMD echo "what an awesome plugin!"
+
+Tell Tutor that the "build" folder should be recursively rendered to ``env/plugins/myplugin/build`` with the :py:data:`tutor.hooks.Filters.ENV_TEMPLATE_TARGETS`::
+
+    hooks.Filters.ENV_TEMPLATE_TARGETS.add_item(
+        ("myplugin/build", "plugins")
+    )
+
+At this point you can verify that the Dockerfile template was properly rendered::
+
+    $ cat "$(tutor config printroot)/env/plugins/myplugin/build/myservice/Dockerfile"
+    FROM docker.io/debian:bullseye-slim
+    CMD echo "what an awesome plugin!"
+
+We would like to build this image by running ``tutor images build myservice``. For that, we use the :py:data:`tutor.hooks.Filters.IMAGES_BUILD` filter::
+
+    hooks.Filters.IMAGES_BUILD.add_item(
+        (
+            "myservice", # same name that will be passed to the `build` command
+            ("plugins", "myplugin", "build", "myservice"), # path to the Dockerfile folder
+            "myservice:latest", # Docker image tag
+            (), # custom build arguments that will be passed to the `docker build` command
+        )
+    )
+
+You can now build your image::
+
+    $ tutor images build myservice
+    Building image myservice:latest
+    docker build -t myservice:latest /home/yourusername/.local/share/tutor/env/plugins/myplugin/build/myservice
+    ...
+    Successfully tagged myservice:latest
+
+Similarly, to push/pull your image to/from a Docker registry, implement the :py:data:`tutor.hooks.Filters.IMAGES_PUSH` and :py:data:`tutor.hooks.Filters.IMAGES_PULL` filters::
+
+    hooks.Filters.IMAGES_PUSH.add_item(("myservice", "myservice:latest"))
+    hooks.Filters.IMAGES_PULL.add_item(("myservice", "myservice:latest"))
+
+You can now run::
+
+    $ tutor images push myservice
+    $ tutor images pull myservice
+
+The "myservice" container can be automatically run in local installations by implementing the :patch:`local-docker-compose-services` patch::
+
+    hooks.Filters.ENV_PATCHES.add_item(
+        (
+            "local-docker-compose-services",
+            """
+    myservice:
+        image: myservice:latest
+    """
+        )
+    )
+
+You can now run the "myservice" container which will execute the ``CMD`` statement we wrote in the Dockerfile::
+
+    $ tutor config save && tutor local run myservice
+    ...
+    Creating tutor_local_myservice_run ... done
+    what an awesome plugin!
+
+Declaring initialisation tasks
+------------------------------
+
+Services often need to run specific tasks before they can be started. For instance, the LMS and the CMS need to apply database migrations. These commands are written in shell scripts that are executed whenever we run ``quickstart``. We call these scripts "init tasks". To add a new local init task, we must first add the corresponding service to the ``docker-compose-jobs.yml`` file by implementing the :patch:`local-docker-compose-jobs-services` patch::
+
+    hooks.Filters.ENV_PATCHES.add_item(
+        (
+            "local-docker-compose-jobs-services",
+            """
+    myservice-job:
+        image: myservice:latest
+    """,
+        )
+    )
+
+The patch above defined the "myservice-job" container which will run our initialisation task. Make sure that it is applied by updating your environment::
+
+    $ tutor config save
+
+Next, we create the folder which will contain our init task script::
+
+    $ mkdir "$(tutor plugins printroot)/templates/myplugin/tasks"
+
+Edit ``$(tutor plugins printroot)/templates/myplugin/tasks/init.sh``::
+
+    echo "++++++ initialising my plugin..."
+    echo "++++++ done!"
+
+Add our init task script to the :py:data:`tutor.hooks.Filters.COMMANDS_INIT` filter::
+
+    hooks.Filters.COMMANDS_INIT.add_item(
+        ("myservice", ("myplugin", "tasks", "init.sh")),
+    )
+
+Run this initialisation task with::
+
+    $ tutor local init --limit=myplugin
+    ...
+    Running init task: myplugin/tasks/init.sh
+    ...
+    Creating tutor_local_myservice-job_run ... done
+    ++++++ initialising my plugin...
+    ++++++ done!
+    All services initialised.
+
+Final result
+------------
+
+Eventually, our plugin is composed of the following files, all stored within the folder indicated by ``tutor plugins printroot`` (on Linux: ``~/.local/share/tutor-plugins``).
+
+``myplugin.py``
+~~~~~~~~~~~~~~~
+
+::
+
+    import os
+    from tutor import hooks
+
+    # Define extra folder to look for templates and render the content of the "build" folder
+    template_folder = os.path.join(os.path.dirname(__file__), "templates")
+    hooks.Filters.ENV_TEMPLATE_ROOTS.add_item(template_folder)
+    hooks.Filters.ENV_TEMPLATE_TARGETS.add_item(
+        ("myplugin/build", "plugins")
+    )
+
+    # Define patches
+    hooks.Filters.ENV_PATCHES.add_item(
+        (
+            "openedx-lms-common-settings",
+            "FEATURES['ALLOW_PUBLIC_ACCOUNT_CREATION'] = False"
+        )
+    )
+    hooks.Filters.ENV_PATCHES.add_item(
+        (
+            "openedx-lms-common-settings",
+            "FEATURES['ALLOW_PUBLIC_ACCOUNT_CREATION'] = {% if MYPLUGIN_PLATFORM_IS_PUBLIC %}True{% else %}False{% endif %}",
+        )
+    )
+    hooks.Filters.ENV_PATCHES.add_item(
+        (
+            "local-docker-compose-services",
+            """
+    myservice:
+        image: myservice:latest
+    """
+        )
+    )
+    hooks.Filters.ENV_PATCHES.add_item(
+        (
+            "local-docker-compose-jobs-services",
+            """
+    myservice-job:
+        image: myservice:latest
+    """,
+        )
+    )
+
+    # Modify configuration
+    hooks.Filters.CONFIG_DEFAULTS.add_item(
+        ("MYPLUGIN_PLATFORM_IS_PUBLIC", False)
+    )
+
+    # Define tasks
+    hooks.Filters.IMAGES_BUILD.add_item(
+        (
+            "myservice",
+            ("plugins", "myplugin", "build", "myservice"),
+            "myservice:latest",
+            (),
+        )
+    )
+    hooks.Filters.IMAGES_PUSH.add_item(("myservice", "myservice:latest"))
+    hooks.Filters.IMAGES_PULL.add_item(("myservice", "myservice:latest"))
+    hooks.Filters.COMMANDS_INIT.add_item(
+        ("myservice", ("myplugin", "tasks", "init.sh")),
+    )
+
+``templates/myplugin/build/myservice/Dockerfile``
+~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
+
+::
+
+    FROM docker.io/debian:bullseye-slim
+    CMD echo "what an awesome plugin!"
+
+``templates/myplugin/tasks/init.sh``
+~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
+
+::
+
+    echo "initialising my plugin..."
+    echo "done!"
+
+Distributing a plugin as a Python package
+=========================================
+
+Storing plugins as simple Python modules has the merit of simplicity, but it makes it more difficult to distribute them, either to other users or to remote servers. When your plugin grows more complex, it is recommended to migrate it to a Python package. You should create a package using the `plugin cookiecutter <https://github.com/overhangio/cookiecutter-tutor-plugin>`__. Packages are automatically detected as plugins thanks to the "tutor.plugin.v1" `entry point <https://setuptools.pypa.io/en/latest/userguide/entry_point.html#advertising-behavior>`__. The modules indicated by this entry point will be automatically imported when the plugins are enabled. See the cookiecutter project `README <https://github.com/overhangio/cookiecutter-tutor-plugin/blob/master/README.rst>`__ for more information.

requirements/base.txt

@@ -26,7 +26,7 @@ kubernetes==18.20.0
     # via -r requirements/base.in
 markupsafe==2.0.1
     # via jinja2
-mypy==0.931
+mypy==0.942
     # via -r requirements/base.in
 mypy-extensions==0.4.3
     # via mypy

requirements/dev.in

@@ -7,5 +7,6 @@ twine
 coverage
 
 # Types packages
+types-docutils
 types-PyYAML
 types-setuptools

requirements/dev.txt

@@ -10,7 +10,7 @@ appdirs==1.4.4
     # via -r requirements/base.txt
 astroid==2.8.3
     # via pylint
-black==21.9b0
+black==22.1.0
     # via -r requirements/dev.in
 bleach==4.1.0
     # via readme-renderer
@@ -74,7 +74,7 @@ markupsafe==2.0.1
     #   jinja2
 mccabe==0.6.1
     # via pylint
-mypy==0.910
+mypy==0.942
     # via -r requirements/base.txt
 mypy-extensions==0.4.3
     # via
@@ -132,8 +132,6 @@ pyyaml==6.0
     #   kubernetes
 readme-renderer==30.0
     # via twine
-regex==2021.10.23
-    # via black
 requests==2.26.0
     # via
     #   -r requirements/base.txt
@@ -163,18 +161,19 @@ six==1.16.0
     #   kubernetes
     #   python-dateutil
 toml==0.10.2
+    # via pylint
+tomli==2.0.1
     # via
     #   -r requirements/base.txt
-    #   mypy
-    #   pylint
-tomli==1.2.2
-    # via
     #   black
+    #   mypy
     #   pep517
 tqdm==4.62.3
     # via twine
 twine==3.4.2
     # via -r requirements/dev.in
+types-docutils==0.18.0
+    # via -r requirements/dev.in
 types-pyyaml==6.0.0
     # via -r requirements/dev.in
 types-setuptools==57.4.2

requirements/docs.txt

@@ -52,7 +52,7 @@ markupsafe==2.0.1
     # via
     #   -r requirements/base.txt
     #   jinja2
-mypy==0.910
+mypy==0.942
     # via -r requirements/base.txt
 mypy-extensions==0.4.3
     # via
@@ -132,7 +132,7 @@ sphinxcontrib-qthelp==1.0.3
     # via sphinx
 sphinxcontrib-serializinghtml==1.1.5
     # via sphinx
-toml==0.10.2
+tomli==2.0.1
     # via
     #   -r requirements/base.txt
     #   mypy

tests/commands/base.py

@@ -0,0 +1,35 @@
+import typing as t
+
+import click.testing
+
+from tests.helpers import TestContext, temporary_root
+from tutor.commands.cli import cli
+
+
+class TestCommandMixin:
+    """
+    Run CLI tests in an isolated test root.
+    """
+
+    @staticmethod
+    def invoke(args: t.List[str]) -> click.testing.Result:
+        with temporary_root() as root:
+            return TestCommandMixin.invoke_in_root(root, args)
+
+    @staticmethod
+    def invoke_in_root(root: str, args: t.List[str]) -> click.testing.Result:
+        """
+        Use this method for commands that all need to run in the same root:
+
+            with temporary_root() as root:
+                result1 = self.invoke_in_root(root, ...)
+                result2 = self.invoke_in_root(root, ...)
+        """
+        runner = click.testing.CliRunner(
+            env={
+                "TUTOR_ROOT": root,
+                "TUTOR_IGNORE_ENTRYPOINT_PLUGINS": "1",
+                "TUTOR_IGNORE_DICT_PLUGINS": "1",
+            }
+        )
+        return runner.invoke(cli, args, obj=TestContext(root))

tests/commands/test_cli.py

@@ -1,27 +1,23 @@
 import unittest
 
-from click.testing import CliRunner
-
 from tutor.__about__ import __version__
-from tutor.commands.cli import cli, print_help
+
+from .base import TestCommandMixin
 
 
-class CliTests(unittest.TestCase):
+class CliTests(unittest.TestCase, TestCommandMixin):
     def test_help(self) -> None:
-        runner = CliRunner()
-        result = runner.invoke(print_help)
+        result = self.invoke(["help"])
         self.assertEqual(0, result.exit_code)
         self.assertIsNone(result.exception)
 
     def test_cli_help(self) -> None:
-        runner = CliRunner()
-        result = runner.invoke(cli, ["--help"])
+        result = self.invoke(["--help"])
         self.assertEqual(0, result.exit_code)
         self.assertIsNone(result.exception)
 
     def test_cli_version(self) -> None:
-        runner = CliRunner()
-        result = runner.invoke(cli, ["--version"])
+        result = self.invoke(["--version"])
         self.assertEqual(0, result.exit_code)
         self.assertIsNone(result.exception)
-        self.assertRegex(result.output, r"cli, version {}\n".format(__version__))
+        self.assertRegex(result.output, rf"cli, version {__version__}\n")

tests/commands/test_config.py

@@ -2,115 +2,88 @@ import os
 import tempfile
 import unittest
 
-from click.testing import CliRunner
-
-from tests.helpers import TestContext, temporary_root
+from tests.helpers import temporary_root
 from tutor import config as tutor_config
-from tutor.commands.config import config_command
+
+from .base import TestCommandMixin
 
 
-class ConfigTests(unittest.TestCase):
+class ConfigTests(unittest.TestCase, TestCommandMixin):
     def test_config_help(self) -> None:
-        runner = CliRunner()
-        result = runner.invoke(config_command, ["--help"])
+        result = self.invoke(["config", "--help"])
         self.assertEqual(0, result.exit_code)
         self.assertFalse(result.exception)
 
     def test_config_save(self) -> None:
-        with temporary_root() as root:
-            context = TestContext(root)
-            runner = CliRunner()
-            result = runner.invoke(config_command, ["save"], obj=context)
-            self.assertEqual(0, result.exit_code)
-            self.assertFalse(result.exception)
+        result = self.invoke(["config", "save"])
+        self.assertFalse(result.exception)
+        self.assertEqual(0, result.exit_code)
 
     def test_config_save_interactive(self) -> None:
-        with temporary_root() as root:
-            context = TestContext(root)
-            runner = CliRunner()
-            result = runner.invoke(config_command, ["save", "-i"], obj=context)
-            self.assertEqual(0, result.exit_code)
-            self.assertFalse(result.exception)
+        result = self.invoke(["config", "save", "-i"])
+        self.assertFalse(result.exception)
+        self.assertEqual(0, result.exit_code)
 
     def test_config_save_skip_update(self) -> None:
-        with temporary_root() as root:
-            context = TestContext(root)
-            runner = CliRunner()
-            result = runner.invoke(config_command, ["save", "-e"], obj=context)
-            self.assertEqual(0, result.exit_code)
-            self.assertFalse(result.exception)
+        result = self.invoke(["config", "save", "-e"])
+        self.assertFalse(result.exception)
+        self.assertEqual(0, result.exit_code)
 
     def test_config_save_set_value(self) -> None:
         with temporary_root() as root:
-            context = TestContext(root)
-            runner = CliRunner()
-            result = runner.invoke(
-                config_command, ["save", "-s", "key=value"], obj=context
-            )
-            self.assertEqual(0, result.exit_code)
-            self.assertFalse(result.exception)
-            result = runner.invoke(config_command, ["printvalue", "key"], obj=context)
-            self.assertIn("value", result.output)
+            result1 = self.invoke_in_root(root, ["config", "save", "-s", "key=value"])
+            result2 = self.invoke_in_root(root, ["config", "printvalue", "key"])
+        self.assertFalse(result1.exception)
+        self.assertEqual(0, result1.exit_code)
+        self.assertIn("value", result2.output)
 
     def test_config_save_unset_value(self) -> None:
         with temporary_root() as root:
-            context = TestContext(root)
-            runner = CliRunner()
-            result = runner.invoke(config_command, ["save", "-U", "key"], obj=context)
-            self.assertEqual(0, result.exit_code)
-            self.assertFalse(result.exception)
-            result = runner.invoke(config_command, ["printvalue", "key"], obj=context)
-            self.assertEqual(1, result.exit_code)
+            result1 = self.invoke_in_root(root, ["config", "save", "-U", "key"])
+            result2 = self.invoke_in_root(root, ["config", "printvalue", "key"])
+        self.assertFalse(result1.exception)
+        self.assertEqual(0, result1.exit_code)
+        self.assertEqual(1, result2.exit_code)
 
     def test_config_printroot(self) -> None:
         with temporary_root() as root:
-            context = TestContext(root)
-            runner = CliRunner()
-            result = runner.invoke(config_command, ["printroot"], obj=context)
-            self.assertEqual(0, result.exit_code)
-            self.assertFalse(result.exception)
-            self.assertIn(context.root, result.output)
+            result = self.invoke_in_root(root, ["config", "printroot"])
+        self.assertFalse(result.exception)
+        self.assertEqual(0, result.exit_code)
+        self.assertIn(root, result.output)
 
     def test_config_printvalue(self) -> None:
         with temporary_root() as root:
-            context = TestContext(root)
-            runner = CliRunner()
-            runner.invoke(config_command, ["save"], obj=context)
-            result = runner.invoke(
-                config_command, ["printvalue", "MYSQL_ROOT_PASSWORD"], obj=context
+            self.invoke_in_root(root, ["config", "save"])
+            result = self.invoke_in_root(
+                root, ["config", "printvalue", "MYSQL_ROOT_PASSWORD"]
             )
-            self.assertEqual(0, result.exit_code)
-            self.assertFalse(result.exception)
-            self.assertTrue(result.output)
+        self.assertFalse(result.exception)
+        self.assertEqual(0, result.exit_code)
+        self.assertTrue(result.output)
 
     def test_config_render(self) -> None:
         with tempfile.TemporaryDirectory() as dest:
             with temporary_root() as root:
-                context = TestContext(root)
-                runner = CliRunner()
-                runner.invoke(config_command, ["save"], obj=context)
-                result = runner.invoke(
-                    config_command, ["render", context.root, dest], obj=context
-                )
-                self.assertEqual(0, result.exit_code)
-                self.assertFalse(result.exception)
+                self.invoke_in_root(root, ["config", "save"])
+                result = self.invoke_in_root(root, ["config", "render", root, dest])
+        self.assertEqual(0, result.exit_code)
+        self.assertFalse(result.exception)
 
     def test_config_render_with_extra_configs(self) -> None:
         with tempfile.TemporaryDirectory() as dest:
             with temporary_root() as root:
-                context = TestContext(root)
-                runner = CliRunner()
-                runner.invoke(config_command, ["save"], obj=context)
-                result = runner.invoke(
-                    config_command,
+                self.invoke_in_root(root, ["config", "save"])
+                result = self.invoke_in_root(
+                    root,
                     [
+                        "config",
                         "render",
                         "-x",
-                        os.path.join(context.root, tutor_config.CONFIG_FILENAME),
-                        context.root,
+                        os.path.join(root, tutor_config.CONFIG_FILENAME),
+                        root,
                         dest,
                     ],
-                    obj=context,
                 )
-                self.assertEqual(0, result.exit_code)
-                self.assertFalse(result.exception)
+        self.assertEqual(0, result.exit_code)
+        self.assertFalse(result.exception)

tests/commands/test_dev.py

@@ -1,20 +1,15 @@
 import unittest
 
-from click.testing import CliRunner
-
-from tutor.commands.compose import bindmount_command
-from tutor.commands.dev import dev
+from .base import TestCommandMixin
 
 
-class DevTests(unittest.TestCase):
+class DevTests(unittest.TestCase, TestCommandMixin):
     def test_dev_help(self) -> None:
-        runner = CliRunner()
-        result = runner.invoke(dev, ["--help"])
+        result = self.invoke(["dev", "--help"])
         self.assertEqual(0, result.exit_code)
         self.assertIsNone(result.exception)
 
     def test_dev_bindmount(self) -> None:
-        runner = CliRunner()
-        result = runner.invoke(bindmount_command, ["--help"])
+        result = self.invoke(["dev", "bindmount", "--help"])
         self.assertEqual(0, result.exit_code)
         self.assertIsNone(result.exception)

tests/commands/test_images.py

@@ -1,177 +1,145 @@
-import unittest
 from unittest.mock import Mock, patch
 
-from click.testing import CliRunner
-
-from tests.helpers import TestContext, temporary_root
-from tutor.__about__ import __version__
+from tests.helpers import PluginsTestCase, temporary_root
 from tutor import images, plugins
-from tutor.commands.config import config_command
-from tutor.commands.images import ImageNotFoundError, images_command
+from tutor.__about__ import __version__
+from tutor.commands.images import ImageNotFoundError
+
+from .base import TestCommandMixin
 
 
-class ImagesTests(unittest.TestCase):
+class ImagesTests(PluginsTestCase, TestCommandMixin):
     def test_images_help(self) -> None:
-        runner = CliRunner()
-        result = runner.invoke(images_command, ["--help"])
-        self.assertEqual(0, result.exit_code)
+        result = self.invoke(["images", "--help"])
         self.assertIsNone(result.exception)
+        self.assertEqual(0, result.exit_code)
 
     def test_images_pull_image(self) -> None:
-        with temporary_root() as root:
-            context = TestContext(root)
-            runner = CliRunner()
-            result = runner.invoke(images_command, ["pull"], obj=context)
-            self.assertEqual(0, result.exit_code)
-            self.assertIsNone(result.exception)
+        result = self.invoke(["images", "pull"])
+        self.assertIsNone(result.exception)
+        self.assertEqual(0, result.exit_code)
 
     def test_images_pull_plugin_invalid_plugin_should_throw_error(self) -> None:
-        with temporary_root() as root:
-            context = TestContext(root)
-            runner = CliRunner()
-            result = runner.invoke(images_command, ["pull", "plugin"], obj=context)
-            self.assertEqual(1, result.exit_code)
-            self.assertEqual(ImageNotFoundError, type(result.exception))
+        result = self.invoke(["images", "pull", "plugin"])
+        self.assertEqual(1, result.exit_code)
+        self.assertEqual(ImageNotFoundError, type(result.exception))
 
-    @patch.object(plugins.BasePlugin, "iter_installed", return_value=[])
-    @patch.object(
-        plugins.Plugins,
-        "iter_hooks",
-        return_value=[
-            (
-                "dev-plugins",
-                {"plugin": "plugin:dev-1.0.0", "plugin2": "plugin2:dev-1.0.0"},
-            )
-        ],
-    )
     @patch.object(images, "pull", return_value=None)
-    def test_images_pull_plugin(
-        self, _image_pull: Mock, iter_hooks: Mock, iter_installed: Mock
-    ) -> None:
-        with temporary_root() as root:
-            context = TestContext(root)
-            runner = CliRunner()
-            result = runner.invoke(images_command, ["pull", "plugin"], obj=context)
-            self.assertEqual(0, result.exit_code)
-            self.assertIsNone(result.exception)
-            iter_hooks.assert_called_once_with("remote-image")
-            _image_pull.assert_called_once_with("plugin:dev-1.0.0")
-            iter_installed.assert_called()
+    def test_images_pull_plugin(self, image_pull: Mock) -> None:
+        plugins.v0.DictPlugin(
+            {
+                "name": "plugin1",
+                "hooks": {
+                    "remote-image": {
+                        "service1": "service1:1.0.0",
+                        "service2": "service2:2.0.0",
+                    }
+                },
+            }
+        )
+        plugins.load("plugin1")
+        result = self.invoke(["images", "pull", "service1"])
+        self.assertIsNone(result.exception)
+        self.assertEqual(0, result.exit_code)
+        image_pull.assert_called_once_with("service1:1.0.0")
+
+    @patch.object(images, "pull", return_value=None)
+    def test_images_pull_all_vendor_images(self, image_pull: Mock) -> None:
+        result = self.invoke(["images", "pull", "mysql"])
+        self.assertIsNone(result.exception)
+        self.assertEqual(0, result.exit_code)
+        # Note: we should update this tag whenever the mysql image is updated
+        image_pull.assert_called_once_with("docker.io/mysql:5.7.35")
 
     def test_images_printtag_image(self) -> None:
-        with temporary_root() as root:
-            context = TestContext(root)
-            runner = CliRunner()
-            result = runner.invoke(images_command, ["printtag", "openedx"], obj=context)
-            self.assertEqual(0, result.exit_code)
-            self.assertIsNone(result.exception)
-            self.assertRegex(
-                result.output, r"docker.io/overhangio/openedx:{}\n".format(__version__)
-            )
+        result = self.invoke(["images", "printtag", "openedx"])
+        self.assertIsNone(result.exception)
+        self.assertEqual(0, result.exit_code)
+        self.assertRegex(
+            result.output, rf"docker.io/overhangio/openedx:{__version__}\n"
+        )
 
-    @patch.object(plugins.BasePlugin, "iter_installed", return_value=[])
-    @patch.object(
-        plugins.Plugins,
-        "iter_hooks",
-        return_value=[
-            (
-                "dev-plugins",
-                {"plugin": "plugin:dev-1.0.0", "plugin2": "plugin2:dev-1.0.0"},
-            )
-        ],
-    )
-    def test_images_printtag_plugin(
-        self, iter_hooks: Mock, iter_installed: Mock
-    ) -> None:
-        with temporary_root() as root:
-            context = TestContext(root)
-            runner = CliRunner()
-            result = runner.invoke(images_command, ["printtag", "plugin"], obj=context)
-            self.assertEqual(0, result.exit_code)
-            self.assertIsNone(result.exception)
-            iter_hooks.assert_called_once_with("build-image")
-            iter_installed.assert_called()
-            self.assertEqual(result.output, "plugin:dev-1.0.0\n")
+    def test_images_printtag_plugin(self) -> None:
+        plugins.v0.DictPlugin(
+            {
+                "name": "plugin1",
+                "hooks": {
+                    "build-image": {
+                        "service1": "service1:1.0.0",
+                        "service2": "service2:2.0.0",
+                    }
+                },
+            }
+        )
+        plugins.load("plugin1")
+        result = self.invoke(["images", "printtag", "service1"])
+        self.assertIsNone(result.exception)
+        self.assertEqual(0, result.exit_code, result)
+        self.assertEqual(result.output, "service1:1.0.0\n")
 
-    @patch.object(plugins.BasePlugin, "iter_installed", return_value=[])
-    @patch.object(
-        plugins.Plugins,
-        "iter_hooks",
-        return_value=[
-            (
-                "dev-plugins",
-                {"plugin": "plugin:dev-1.0.0", "plugin2": "plugin2:dev-1.0.0"},
-            )
-        ],
-    )
     @patch.object(images, "build", return_value=None)
-    def test_images_build_plugin(
-        self, image_build: Mock, iter_hooks: Mock, iter_installed: Mock
-    ) -> None:
+    def test_images_build_plugin(self, mock_image_build: Mock) -> None:
+        plugins.v0.DictPlugin(
+            {
+                "name": "plugin1",
+                "hooks": {
+                    "build-image": {
+                        "service1": "service1:1.0.0",
+                        "service2": "service2:2.0.0",
+                    }
+                },
+            }
+        )
+        plugins.load("plugin1")
         with temporary_root() as root:
-            context = TestContext(root)
-            runner = CliRunner()
-            runner.invoke(config_command, ["save"], obj=context)
-            result = runner.invoke(images_command, ["build", "plugin"], obj=context)
-            self.assertIsNone(result.exception)
-            self.assertEqual(0, result.exit_code)
-            image_build.assert_called()
-            iter_hooks.assert_called_once_with("build-image")
-            iter_installed.assert_called()
-            self.assertIn("plugin:dev-1.0.0", image_build.call_args[0])
+            self.invoke_in_root(root, ["config", "save"])
+            result = self.invoke_in_root(root, ["images", "build", "service1"])
+        self.assertIsNone(result.exception)
+        self.assertEqual(0, result.exit_code)
+        mock_image_build.assert_called()
+        self.assertIn("service1:1.0.0", mock_image_build.call_args[0])
 
-    @patch.object(plugins.BasePlugin, "iter_installed", return_value=[])
-    @patch.object(
-        plugins.Plugins,
-        "iter_hooks",
-        return_value=[
-            (
-                "dev-plugins",
-                {"plugin": "plugin:dev-1.0.0", "plugin2": "plugin2:dev-1.0.0"},
-            )
-        ],
-    )
     @patch.object(images, "build", return_value=None)
-    def test_images_build_plugin_with_args(
-        self, image_build: Mock, iter_hooks: Mock, iter_installed: Mock
-    ) -> None:
+    def test_images_build_plugin_with_args(self, image_build: Mock) -> None:
+        plugins.v0.DictPlugin(
+            {
+                "name": "plugin1",
+                "hooks": {
+                    "build-image": {
+                        "service1": "service1:1.0.0",
+                        "service2": "service2:2.0.0",
+                    }
+                },
+            }
+        )
+        plugins.load("plugin1")
+        build_args = [
+            "images",
+            "build",
+            "--no-cache",
+            "-a",
+            "myarg=value",
+            "--add-host",
+            "host",
+            "--target",
+            "target",
+            "-d",
+            "docker_args",
+            "service1",
+        ]
         with temporary_root() as root:
-            context = TestContext(root)
-            runner = CliRunner()
-            runner.invoke(config_command, ["save"], obj=context)
-            args = [
-                "build",
-                "--no-cache",
-                "-a",
-                "myarg=value",
-                "--add-host",
-                "host",
-                "--target",
-                "target",
-                "-d",
-                "docker_args",
-                "plugin",
-            ]
-            result = runner.invoke(
-                images_command,
-                args,
-                obj=context,
-            )
-            self.assertEqual(0, result.exit_code)
-            self.assertIsNone(result.exception)
-            iter_hooks.assert_called_once_with("build-image")
-            iter_installed.assert_called()
-            image_build.assert_called()
-            self.assertIn("plugin:dev-1.0.0", image_build.call_args[0])
-            for arg in image_build.call_args[0][2:]:
-                if arg == "--build-arg":
-                    continue
-                self.assertIn(arg, args)
+            self.invoke_in_root(root, ["config", "save"])
+            result = self.invoke_in_root(root, build_args)
+        self.assertIsNone(result.exception)
+        self.assertEqual(0, result.exit_code)
+        image_build.assert_called()
+        self.assertIn("service1:1.0.0", image_build.call_args[0])
+        for arg in image_build.call_args[0][2:]:
+            # The only extra args are `--build-arg`
+            if arg != "--build-arg":
+                self.assertIn(arg, build_args)
 
     def test_images_push(self) -> None:
-        with temporary_root() as root:
-            context = TestContext(root)
-            runner = CliRunner()
-            result = runner.invoke(images_command, ["push"], obj=context)
-            self.assertEqual(0, result.exit_code)
-            self.assertIsNone(result.exception)
+        result = self.invoke(["images", "push"])
+        self.assertIsNone(result.exception)
+        self.assertEqual(0, result.exit_code)

tests/commands/test_k8s.py

@@ -1,13 +1,10 @@
 import unittest
 
-from click.testing import CliRunner
-
-from tutor.commands.k8s import k8s
+from .base import TestCommandMixin
 
 
-class K8sTests(unittest.TestCase):
+class K8sTests(unittest.TestCase, TestCommandMixin):
     def test_k8s_help(self) -> None:
-        runner = CliRunner()
-        result = runner.invoke(k8s, ["--help"])
-        self.assertEqual(0, result.exit_code)
+        result = self.invoke(["k8s", "--help"])
         self.assertIsNone(result.exception)
+        self.assertEqual(0, result.exit_code)

tests/commands/test_local.py

@@ -1,25 +1,20 @@
 import unittest
 
-from click.testing import CliRunner
-
-from tutor.commands.local import local, quickstart, upgrade
+from .base import TestCommandMixin
 
 
-class LocalTests(unittest.TestCase):
+class LocalTests(unittest.TestCase, TestCommandMixin):
     def test_local_help(self) -> None:
-        runner = CliRunner()
-        result = runner.invoke(local, ["--help"])
-        self.assertEqual(0, result.exit_code)
+        result = self.invoke(["local", "--help"])
         self.assertIsNone(result.exception)
+        self.assertEqual(0, result.exit_code)
 
     def test_local_quickstart_help(self) -> None:
-        runner = CliRunner()
-        result = runner.invoke(quickstart, ["--help"])
-        self.assertEqual(0, result.exit_code)
+        result = self.invoke(["local", "quickstart", "--help"])
         self.assertIsNone(result.exception)
+        self.assertEqual(0, result.exit_code)
 
     def test_local_upgrade_help(self) -> None:
-        runner = CliRunner()
-        result = runner.invoke(upgrade, ["--help"])
-        self.assertEqual(0, result.exit_code)
+        result = self.invoke(["local", "upgrade", "--help"])
         self.assertIsNone(result.exception)
+        self.assertEqual(0, result.exit_code)

tests/commands/test_plugins.py

@@ -1,64 +1,42 @@
 import unittest
 from unittest.mock import Mock, patch
 
-from click.testing import CliRunner
-
-from tests.helpers import TestContext, temporary_root
 from tutor import plugins
-from tutor.commands.plugins import plugins_command
+
+from .base import TestCommandMixin
 
 
-class PluginsTests(unittest.TestCase):
+class PluginsTests(unittest.TestCase, TestCommandMixin):
     def test_plugins_help(self) -> None:
-        runner = CliRunner()
-        result = runner.invoke(plugins_command, ["--help"])
-        self.assertEqual(0, result.exit_code)
+        result = self.invoke(["plugins", "--help"])
         self.assertIsNone(result.exception)
+        self.assertEqual(0, result.exit_code)
 
     def test_plugins_printroot(self) -> None:
-        with temporary_root() as root:
-            context = TestContext(root)
-            runner = CliRunner()
-            result = runner.invoke(plugins_command, ["printroot"], obj=context)
-            self.assertEqual(0, result.exit_code)
-            self.assertIsNone(result.exception)
-            self.assertTrue(result.output)
+        result = self.invoke(["plugins", "printroot"])
+        self.assertIsNone(result.exception)
+        self.assertEqual(0, result.exit_code)
+        self.assertTrue(result.output)
 
-    @patch.object(plugins.BasePlugin, "iter_installed", return_value=[])
-    def test_plugins_list(self, _iter_installed: Mock) -> None:
-        with temporary_root() as root:
-            context = TestContext(root)
-            runner = CliRunner()
-            result = runner.invoke(plugins_command, ["list"], obj=context)
-            self.assertEqual(0, result.exit_code)
-            self.assertIsNone(result.exception)
-            self.assertFalse(result.output)
-            _iter_installed.assert_called()
+    @patch.object(plugins, "iter_info", return_value=[])
+    def test_plugins_list(self, _iter_info: Mock) -> None:
+        result = self.invoke(["plugins", "list"])
+        self.assertIsNone(result.exception)
+        self.assertEqual(0, result.exit_code)
+        self.assertFalse(result.output)
+        _iter_info.assert_called()
 
     def test_plugins_install_not_found_plugin(self) -> None:
-        with temporary_root() as root:
-            context = TestContext(root)
-            runner = CliRunner()
-            result = runner.invoke(
-                plugins_command, ["install", "notFound"], obj=context
-            )
-            self.assertEqual(1, result.exit_code)
-            self.assertTrue(result.exception)
+        result = self.invoke(["plugins", "install", "notFound"])
+        self.assertEqual(1, result.exit_code)
+        self.assertTrue(result.exception)
 
     def test_plugins_enable_not_installed_plugin(self) -> None:
-        with temporary_root() as root:
-            context = TestContext(root)
-            runner = CliRunner()
-            result = runner.invoke(plugins_command, ["enable", "notFound"], obj=context)
-            self.assertEqual(1, result.exit_code)
-            self.assertTrue(result.exception)
+        result = self.invoke(["plugins", "enable", "notFound"])
+        self.assertEqual(1, result.exit_code)
+        self.assertTrue(result.exception)
 
     def test_plugins_disable_not_installed_plugin(self) -> None:
-        with temporary_root() as root:
-            context = TestContext(root)
-            runner = CliRunner()
-            result = runner.invoke(
-                plugins_command, ["disable", "notFound"], obj=context
-            )
-            self.assertEqual(0, result.exit_code)
-            self.assertFalse(result.exception)
+        result = self.invoke(["plugins", "disable", "notFound"])
+        self.assertEqual(0, result.exit_code)
+        self.assertFalse(result.exception)

tests/helpers.py

@@ -1,25 +1,25 @@
 import os
 import tempfile
+import typing as t
+import unittest
+import unittest.result
 
+from tutor import hooks
 from tutor.commands.context import BaseJobContext
 from tutor.jobs import BaseJobRunner
 from tutor.types import Config
 
 
 class TestJobRunner(BaseJobRunner):
-    def __init__(self, root: str, config: Config):
-        """
-        Mock job runner for unit testing.
+    """
+    Mock job runner for unit testing.
 
-        This runner does nothing except print the service name and command,
-        separated by dashes.
-        """
-        super().__init__(root, config)
+    This runner does nothing except print the service name and command,
+    separated by dashes.
+    """
 
     def run_job(self, service: str, command: str) -> int:
-        print(
-            os.linesep.join(["Service: {}".format(service), "-----", command, "----- "])
-        )
+        print(os.linesep.join([f"Service: {service}", "-----", command, "----- "]))
         return 0
 
 
@@ -43,3 +43,36 @@ class TestContext(BaseJobContext):
 
     def job_runner(self, config: Config) -> TestJobRunner:
         return TestJobRunner(self.root, config)
+
+
+class PluginsTestCase(unittest.TestCase):
+    """
+    This test case class clears the hooks created during tests. It also makes sure that
+    we don't accidentally load entrypoint/dict plugins from the user.
+    """
+
+    def setUp(self) -> None:
+        self.clean()
+        self.addCleanup(self.clean)
+        super().setUp()
+
+    def clean(self) -> None:
+        # We clear hooks created in some contexts, such that user plugins are never loaded.
+        for context in [
+            hooks.Contexts.PLUGINS.name,
+            hooks.Contexts.PLUGINS_V0_ENTRYPOINT.name,
+            hooks.Contexts.PLUGINS_V0_YAML.name,
+            "unittests",
+        ]:
+            hooks.filters.clear_all(context=context)
+            hooks.actions.clear_all(context=context)
+
+    def run(
+        self, result: t.Optional[unittest.result.TestResult] = None
+    ) -> t.Optional[unittest.result.TestResult]:
+        """
+        Run all actions and filters with a test context, such that they can be cleared
+        from one run to the next.
+        """
+        with hooks.contexts.enter("unittests"):
+            return super().run(result=result)

tests/hooks/test_actions.py

@@ -0,0 +1,57 @@
+import typing as t
+import unittest
+
+from tutor import hooks
+
+
+class PluginActionsTests(unittest.TestCase):
+    def setUp(self) -> None:
+        self.side_effect_int = 0
+
+    def tearDown(self) -> None:
+        super().tearDown()
+        hooks.actions.clear_all(context="tests")
+
+    def run(self, result: t.Any = None) -> t.Any:
+        with hooks.contexts.enter("tests"):
+            return super().run(result=result)
+
+    def test_on(self) -> None:
+        @hooks.actions.add("test-action")
+        def _test_action_1(increment: int) -> None:
+            self.side_effect_int += increment
+
+        @hooks.actions.add("test-action")
+        def _test_action_2(increment: int) -> None:
+            self.side_effect_int += increment * 2
+
+        hooks.actions.do("test-action", 1)
+        self.assertEqual(3, self.side_effect_int)
+
+    def test_priority(self) -> None:
+        @hooks.actions.add("test-action", priority=2)
+        def _test_action_1() -> None:
+            self.side_effect_int += 4
+
+        @hooks.actions.add("test-action", priority=1)
+        def _test_action_2() -> None:
+            self.side_effect_int = self.side_effect_int // 2
+
+        # Action 2 must be performed before action 1
+        self.side_effect_int = 4
+        hooks.actions.do("test-action")
+        self.assertEqual(6, self.side_effect_int)
+
+    def test_equal_priority(self) -> None:
+        @hooks.actions.add("test-action", priority=2)
+        def _test_action_1() -> None:
+            self.side_effect_int += 4
+
+        @hooks.actions.add("test-action", priority=2)
+        def _test_action_2() -> None:
+            self.side_effect_int = self.side_effect_int // 2
+
+        # Action 2 must be performed after action 1
+        self.side_effect_int = 4
+        hooks.actions.do("test-action")
+        self.assertEqual(4, self.side_effect_int)

tests/hooks/test_filters.py

@@ -0,0 +1,60 @@
+import typing as t
+import unittest
+
+from tutor import hooks
+
+
+class PluginFiltersTests(unittest.TestCase):
+    def tearDown(self) -> None:
+        super().tearDown()
+        hooks.filters.clear_all(context="tests")
+
+    def run(self, result: t.Any = None) -> t.Any:
+        with hooks.contexts.enter("tests"):
+            return super().run(result=result)
+
+    def test_add(self) -> None:
+        @hooks.filters.add("tests:count-sheeps")
+        def filter1(value: int) -> int:
+            return value + 1
+
+        value = hooks.filters.apply("tests:count-sheeps", 0)
+        self.assertEqual(1, value)
+
+    def test_add_items(self) -> None:
+        @hooks.filters.add("tests:add-sheeps")
+        def filter1(sheeps: t.List[int]) -> t.List[int]:
+            return sheeps + [0]
+
+        hooks.filters.add_item("tests:add-sheeps", 1)
+        hooks.filters.add_item("tests:add-sheeps", 2)
+        hooks.filters.add_items("tests:add-sheeps", [3, 4])
+
+        sheeps: t.List[int] = hooks.filters.apply("tests:add-sheeps", [])
+        self.assertEqual([0, 1, 2, 3, 4], sheeps)
+
+    def test_filter_callbacks(self) -> None:
+        callback = hooks.filters.FilterCallback(lambda _: 1)
+        self.assertTrue(callback.is_in_context(None))
+        self.assertFalse(callback.is_in_context("customcontext"))
+        self.assertEqual(1, callback.apply(0))
+        self.assertEqual(0, callback.apply(0, context="customcontext"))
+
+    def test_filter_context(self) -> None:
+        with hooks.contexts.enter("testcontext"):
+            hooks.filters.add_item("test:sheeps", 1)
+        hooks.filters.add_item("test:sheeps", 2)
+
+        self.assertEqual([1, 2], hooks.filters.apply("test:sheeps", []))
+        self.assertEqual(
+            [1], hooks.filters.apply("test:sheeps", [], context="testcontext")
+        )
+
+    def test_clear_context(self) -> None:
+        with hooks.contexts.enter("testcontext"):
+            hooks.filters.add_item("test:sheeps", 1)
+        hooks.filters.add_item("test:sheeps", 2)
+
+        self.assertEqual([1, 2], hooks.filters.apply("test:sheeps", []))
+        hooks.filters.clear("test:sheeps", context="testcontext")
+        self.assertEqual([2], hooks.filters.apply("test:sheeps", []))

tests/test_config.py

@@ -5,15 +5,15 @@ from unittest.mock import Mock, patch
 
 import click
 
-from tests.helpers import temporary_root
+from tests.helpers import PluginsTestCase, temporary_root
 from tutor import config as tutor_config
-from tutor import interactive
+from tutor import hooks, interactive
 from tutor.types import Config, get_typed
 
 
 class ConfigTests(unittest.TestCase):
     def test_version(self) -> None:
-        defaults = tutor_config.get_defaults({})
+        defaults = tutor_config.get_defaults()
         self.assertNotIn("TUTOR_VERSION", defaults)
 
     def test_merge(self) -> None:
@@ -24,7 +24,7 @@ class ConfigTests(unittest.TestCase):
 
     def test_merge_not_render(self) -> None:
         config: Config = {}
-        base = tutor_config.get_base({})
+        base = tutor_config.get_base()
         with patch.object(tutor_config.utils, "random_string", return_value="abcd"):
             tutor_config.merge(config, base)
 
@@ -40,26 +40,6 @@ class ConfigTests(unittest.TestCase):
 
         self.assertEqual(config1, config2)
 
-    @patch.object(tutor_config.fmt, "echo")
-    def test_removed_entry_is_added_on_save(self, _: Mock) -> None:
-        with temporary_root() as root:
-            with patch.object(
-                tutor_config.utils, "random_string"
-            ) as mock_random_string:
-                mock_random_string.return_value = "abcd"
-                config1 = tutor_config.load_full(root)
-                password1 = config1["MYSQL_ROOT_PASSWORD"]
-
-                config1.pop("MYSQL_ROOT_PASSWORD")
-                tutor_config.save_config_file(root, config1)
-
-                mock_random_string.return_value = "efgh"
-                config2 = tutor_config.load_full(root)
-                password2 = config2["MYSQL_ROOT_PASSWORD"]
-
-        self.assertEqual("abcd", password1)
-        self.assertEqual("efgh", password2)
-
     def test_interactive(self) -> None:
         def mock_prompt(*_args: None, **kwargs: str) -> str:
             return kwargs["default"]
@@ -100,3 +80,26 @@ class ConfigTests(unittest.TestCase):
             self.assertTrue(os.path.exists(config_yml_path))
             self.assertFalse(os.path.exists(config_json_path))
             self.assertEqual(config, current)
+
+
+class ConfigPluginTestCase(PluginsTestCase):
+    @patch.object(tutor_config.fmt, "echo")
+    def test_removed_entry_is_added_on_save(self, _: Mock) -> None:
+        with temporary_root() as root:
+            mock_random_string = Mock()
+
+            hooks.Filters.ENV_TEMPLATE_FILTERS.add_item(
+                ("random_string", mock_random_string),
+            )
+            mock_random_string.return_value = "abcd"
+            config1 = tutor_config.load_full(root)
+            password1 = config1.pop("MYSQL_ROOT_PASSWORD")
+
+            tutor_config.save_config_file(root, config1)
+
+            mock_random_string.return_value = "efgh"
+            config2 = tutor_config.load_full(root)
+            password2 = config2["MYSQL_ROOT_PASSWORD"]
+
+        self.assertEqual("abcd", password1)
+        self.assertEqual("efgh", password2)

tests/test_env.py

@@ -3,14 +3,15 @@ import tempfile
 import unittest
 from unittest.mock import Mock, patch
 
-from tutor.__about__ import __version__
+from tests.helpers import PluginsTestCase, temporary_root
 from tutor import config as tutor_config
-from tutor import env, exceptions, fmt
+from tutor import env, exceptions, fmt, plugins
+from tutor.__about__ import __version__
+from tutor.plugins.v0 import DictPlugin
 from tutor.types import Config
-from tests.helpers import temporary_root
 
 
-class EnvTests(unittest.TestCase):
+class EnvTests(PluginsTestCase):
     def test_walk_templates(self) -> None:
         renderer = env.Renderer({}, [env.TEMPLATES_ROOT])
         templates = list(renderer.walk_templates("local"))
@@ -103,15 +104,15 @@ class EnvTests(unittest.TestCase):
     def test_patch(self) -> None:
         patches = {"plugin1": "abcd", "plugin2": "efgh"}
         with patch.object(
-            env.plugins, "iter_patches", return_value=patches.items()
+            env.plugins, "iter_patches", return_value=patches.values()
         ) as mock_iter_patches:
             rendered = env.render_str({}, '{{ patch("location") }}')
-            mock_iter_patches.assert_called_once_with({}, "location")
+            mock_iter_patches.assert_called_once_with("location")
         self.assertEqual("abcd\nefgh", rendered)
 
     def test_patch_separator_suffix(self) -> None:
         patches = {"plugin1": "abcd", "plugin2": "efgh"}
-        with patch.object(env.plugins, "iter_patches", return_value=patches.items()):
+        with patch.object(env.plugins, "iter_patches", return_value=patches.values()):
             rendered = env.render_str(
                 {}, '{{ patch("location", separator=",\n", suffix=",") }}'
             )
@@ -119,11 +120,9 @@ class EnvTests(unittest.TestCase):
 
     def test_plugin_templates(self) -> None:
         with tempfile.TemporaryDirectory() as plugin_templates:
-            # Create plugin
-            plugin1 = env.plugins.DictPlugin(
+            DictPlugin(
                 {"name": "plugin1", "version": "0", "templates": plugin_templates}
             )
-
             # Create two templates
             os.makedirs(os.path.join(plugin_templates, "plugin1", "apps"))
             with open(
@@ -139,36 +138,37 @@ class EnvTests(unittest.TestCase):
             ) as f:
                 f.write("Hello my ID is {{ ID }}")
 
-            # Create configuration
-            config: Config = {"ID": "abcd"}
-
             # Render templates
-            with patch.object(
-                env.plugins,
-                "iter_enabled",
-                return_value=[plugin1],
-            ):
-                with temporary_root() as root:
-                    # Render plugin templates
-                    env.save_plugin_templates(plugin1, root, config)
+            with temporary_root() as root:
+                # Create configuration
+                config: Config = tutor_config.load_full(root)
+                config["ID"] = "Hector Rumblethorpe"
+                plugins.load("plugin1")
+                tutor_config.save_enabled_plugins(config)
 
-                    # Check that plugin template was rendered
-                    dst_unrendered = os.path.join(
-                        root, "env", "plugins", "plugin1", "unrendered.txt"
-                    )
-                    dst_rendered = os.path.join(
-                        root, "env", "plugins", "plugin1", "apps", "rendered.txt"
-                    )
-                    self.assertFalse(os.path.exists(dst_unrendered))
-                    self.assertTrue(os.path.exists(dst_rendered))
-                    with open(dst_rendered, encoding="utf-8") as f:
-                        self.assertEqual("Hello my ID is abcd", f.read())
+                # Render environment
+                with patch.object(fmt, "STDOUT"):
+                    env.save(root, config)
+
+                # Check that plugin template was rendered
+                root_env = os.path.join(root, "env")
+                dst_unrendered = os.path.join(
+                    root_env, "plugins", "plugin1", "unrendered.txt"
+                )
+                dst_rendered = os.path.join(
+                    root_env, "plugins", "plugin1", "apps", "rendered.txt"
+                )
+                self.assertFalse(os.path.exists(dst_unrendered))
+                self.assertTrue(os.path.exists(dst_rendered))
+                with open(dst_rendered, encoding="utf-8") as f:
+                    self.assertEqual("Hello my ID is Hector Rumblethorpe", f.read())
 
     def test_renderer_is_reset_on_config_change(self) -> None:
         with tempfile.TemporaryDirectory() as plugin_templates:
-            plugin1 = env.plugins.DictPlugin(
+            plugin1 = DictPlugin(
                 {"name": "plugin1", "version": "0", "templates": plugin_templates}
             )
+
             # Create one template
             os.makedirs(os.path.join(plugin_templates, plugin1.name))
             with open(
@@ -182,14 +182,12 @@ class EnvTests(unittest.TestCase):
             config: Config = {"PLUGINS": []}
             env1 = env.Renderer.instance(config).environment
 
-            with patch.object(
-                env.plugins,
-                "iter_enabled",
-                return_value=[plugin1],
-            ):
-                # Load env a second time
-                config["PLUGINS"] = ["myplugin"]
-                env2 = env.Renderer.instance(config).environment
+            # Enable plugins
+            plugins.load("plugin1")
+
+            # Load env a second time
+            config["PLUGINS"] = ["myplugin"]
+            env2 = env.Renderer.instance(config).environment
 
             self.assertNotIn("plugin1/myplugin.txt", env1.loader.list_templates())
             self.assertIn("plugin1/myplugin.txt", env2.loader.list_templates())

tests/test_plugins.py

@@ -1,244 +0,0 @@
-import unittest
-from unittest.mock import Mock, patch
-
-from tutor import config as tutor_config
-from tutor import exceptions, fmt, plugins
-from tutor.types import Config, get_typed
-
-
-class PluginsTests(unittest.TestCase):
-    def setUp(self) -> None:
-        plugins.Plugins.clear_cache()
-
-    @patch.object(plugins.DictPlugin, "iter_installed", return_value=[])
-    def test_iter_installed(self, dict_plugin_iter_installed: Mock) -> None:
-        with patch.object(plugins.pkg_resources, "iter_entry_points", return_value=[]):  # type: ignore
-            self.assertEqual([], list(plugins.iter_installed()))
-            dict_plugin_iter_installed.assert_called_once()
-
-    def test_is_installed(self) -> None:
-        self.assertFalse(plugins.is_installed("dummy"))
-
-    @patch.object(plugins.DictPlugin, "iter_installed", return_value=[])
-    def test_official_plugins(self, dict_plugin_iter_installed: Mock) -> None:
-        with patch.object(plugins.importlib, "import_module", return_value=42):  # type: ignore
-            plugin1 = plugins.OfficialPlugin.load("plugin1")
-        with patch.object(plugins.importlib, "import_module", return_value=43):  # type: ignore
-            plugin2 = plugins.OfficialPlugin.load("plugin2")
-        with patch.object(
-            plugins.EntrypointPlugin,
-            "iter_installed",
-            return_value=[plugin1],
-        ):
-            self.assertEqual(
-                [plugin1, plugin2],
-                list(plugins.iter_installed()),
-            )
-        dict_plugin_iter_installed.assert_called_once()
-
-    def test_enable(self) -> None:
-        config: Config = {plugins.CONFIG_KEY: []}
-        with patch.object(plugins, "is_installed", return_value=True):
-            plugins.enable(config, "plugin2")
-            plugins.enable(config, "plugin1")
-        self.assertEqual(["plugin1", "plugin2"], config[plugins.CONFIG_KEY])
-
-    def test_enable_twice(self) -> None:
-        config: Config = {plugins.CONFIG_KEY: []}
-        with patch.object(plugins, "is_installed", return_value=True):
-            plugins.enable(config, "plugin1")
-            plugins.enable(config, "plugin1")
-        self.assertEqual(["plugin1"], config[plugins.CONFIG_KEY])
-
-    def test_enable_not_installed_plugin(self) -> None:
-        config: Config = {"PLUGINS": []}
-        with patch.object(plugins, "is_installed", return_value=False):
-            self.assertRaises(exceptions.TutorError, plugins.enable, config, "plugin1")
-
-    @patch.object(
-        plugins.Plugins,
-        "iter_installed",
-        return_value=[
-            plugins.DictPlugin(
-                {
-                    "name": "plugin1",
-                    "version": "1.0.0",
-                    "config": {"set": {"KEY": "value"}},
-                }
-            ),
-            plugins.DictPlugin(
-                {
-                    "name": "plugin2",
-                    "version": "1.0.0",
-                }
-            ),
-        ],
-    )
-    def test_disable(self, _iter_installed_mock: Mock) -> None:
-        config: Config = {"PLUGINS": ["plugin1", "plugin2"]}
-        with patch.object(fmt, "STDOUT"):
-            plugin = plugins.get_enabled(config, "plugin1")
-            plugins.disable(config, plugin)
-        self.assertEqual(["plugin2"], config["PLUGINS"])
-
-    @patch.object(
-        plugins.Plugins,
-        "iter_installed",
-        return_value=[
-            plugins.DictPlugin(
-                {
-                    "name": "plugin1",
-                    "version": "1.0.0",
-                    "config": {"set": {"KEY": "value"}},
-                }
-            ),
-        ],
-    )
-    def test_disable_removes_set_config(self, _iter_installed_mock: Mock) -> None:
-        config: Config = {"PLUGINS": ["plugin1"], "KEY": "value"}
-        plugin = plugins.get_enabled(config, "plugin1")
-        with patch.object(fmt, "STDOUT"):
-            plugins.disable(config, plugin)
-        self.assertEqual([], config["PLUGINS"])
-        self.assertNotIn("KEY", config)
-
-    def test_none_plugins(self) -> None:
-        config: Config = {plugins.CONFIG_KEY: None}
-        self.assertFalse(plugins.is_enabled(config, "myplugin"))
-
-    def test_patches(self) -> None:
-        class plugin1:
-            patches = {"patch1": "Hello {{ ID }}"}
-
-        with patch.object(
-            plugins.Plugins,
-            "iter_enabled",
-            return_value=[plugins.BasePlugin("plugin1", plugin1)],
-        ):
-            patches = list(plugins.iter_patches({}, "patch1"))
-        self.assertEqual([("plugin1", "Hello {{ ID }}")], patches)
-
-    def test_plugin_without_patches(self) -> None:
-        with patch.object(
-            plugins.Plugins,
-            "iter_enabled",
-            return_value=[plugins.BasePlugin("plugin1", None)],
-        ):
-            patches = list(plugins.iter_patches({}, "patch1"))
-        self.assertEqual([], patches)
-
-    def test_configure(self) -> None:
-        class plugin1:
-            config: Config = {
-                "add": {"PARAM1": "value1", "PARAM2": "value2"},
-                "set": {"PARAM3": "value3"},
-                "defaults": {"PARAM4": "value4"},
-            }
-
-        with patch.object(
-            plugins.Plugins,
-            "iter_enabled",
-            return_value=[plugins.BasePlugin("plugin1", plugin1)],
-        ):
-            base = tutor_config.get_base({})
-            defaults = tutor_config.get_defaults({})
-
-        self.assertEqual(base["PARAM3"], "value3")
-        self.assertEqual(base["PLUGIN1_PARAM1"], "value1")
-        self.assertEqual(base["PLUGIN1_PARAM2"], "value2")
-        self.assertEqual(defaults["PLUGIN1_PARAM4"], "value4")
-
-    def test_configure_set_does_not_override(self) -> None:
-        config: Config = {"ID1": "oldid"}
-
-        class plugin1:
-            config: Config = {"set": {"ID1": "newid", "ID2": "id2"}}
-
-        with patch.object(
-            plugins.Plugins,
-            "iter_enabled",
-            return_value=[plugins.BasePlugin("plugin1", plugin1)],
-        ):
-            tutor_config.update_with_base(config)
-
-        self.assertEqual("oldid", config["ID1"])
-        self.assertEqual("id2", config["ID2"])
-
-    def test_configure_set_random_string(self) -> None:
-        class plugin1:
-            config: Config = {"set": {"PARAM1": "{{ 128|random_string }}"}}
-
-        with patch.object(
-            plugins.Plugins,
-            "iter_enabled",
-            return_value=[plugins.BasePlugin("plugin1", plugin1)],
-        ):
-            config = tutor_config.get_base({})
-        tutor_config.render_full(config)
-
-        self.assertEqual(128, len(get_typed(config, "PARAM1", str)))
-
-    def test_configure_default_value_with_previous_definition(self) -> None:
-        config: Config = {"PARAM1": "value"}
-
-        class plugin1:
-            config: Config = {"defaults": {"PARAM2": "{{ PARAM1 }}"}}
-
-        with patch.object(
-            plugins.Plugins,
-            "iter_enabled",
-            return_value=[plugins.BasePlugin("plugin1", plugin1)],
-        ):
-            tutor_config.update_with_defaults(config)
-        self.assertEqual("{{ PARAM1 }}", config["PLUGIN1_PARAM2"])
-
-    def test_config_load_from_plugins(self) -> None:
-        config: Config = {}
-
-        class plugin1:
-            config: Config = {"add": {"PARAM1": "{{ 10|random_string }}"}}
-
-        with patch.object(
-            plugins.Plugins,
-            "iter_enabled",
-            return_value=[plugins.BasePlugin("plugin1", plugin1)],
-        ):
-            tutor_config.update_with_base(config)
-            tutor_config.update_with_defaults(config)
-        tutor_config.render_full(config)
-        value1 = get_typed(config, "PLUGIN1_PARAM1", str)
-
-        self.assertEqual(10, len(value1))
-
-    def test_hooks(self) -> None:
-        class plugin1:
-            hooks = {"init": ["myclient"]}
-
-        with patch.object(
-            plugins.Plugins,
-            "iter_enabled",
-            return_value=[plugins.BasePlugin("plugin1", plugin1)],
-        ):
-            self.assertEqual(
-                [("plugin1", ["myclient"])], list(plugins.iter_hooks({}, "init"))
-            )
-
-    def test_plugins_are_updated_on_config_change(self) -> None:
-        config: Config = {"PLUGINS": []}
-        plugins1 = plugins.Plugins(config)
-        self.assertEqual(0, len(list(plugins1.iter_enabled())))
-        config["PLUGINS"] = ["plugin1"]
-        with patch.object(
-            plugins.Plugins,
-            "iter_installed",
-            return_value=[plugins.BasePlugin("plugin1", None)],
-        ):
-            plugins2 = plugins.Plugins(config)
-            self.assertEqual(1, len(list(plugins2.iter_enabled())))
-
-    def test_dict_plugin(self) -> None:
-        plugin = plugins.DictPlugin(
-            {"name": "myplugin", "config": {"set": {"KEY": "value"}}, "version": "0.1"}
-        )
-        self.assertEqual("myplugin", plugin.name)
-        self.assertEqual({"KEY": "value"}, plugin.config_set)

tests/test_plugins_v0.py

@@ -0,0 +1,222 @@
+import typing as t
+from unittest.mock import patch
+
+from tests.helpers import PluginsTestCase, temporary_root
+from tutor import config as tutor_config
+from tutor import exceptions, fmt, hooks, plugins
+from tutor.plugins import v0 as plugins_v0
+from tutor.types import Config, get_typed
+
+
+class PluginsTests(PluginsTestCase):
+    def test_iter_installed(self) -> None:
+        self.assertEqual([], list(plugins.iter_installed()))
+
+    def test_is_installed(self) -> None:
+        self.assertFalse(plugins.is_installed("dummy"))
+
+    def test_official_plugins(self) -> None:
+        # Create 2 official plugins
+        plugins_v0.OfficialPlugin("plugin1")
+        plugins_v0.OfficialPlugin("plugin2")
+        self.assertEqual(
+            ["plugin1", "plugin2"],
+            list(plugins.iter_installed()),
+        )
+
+    def test_load(self) -> None:
+        config: Config = {tutor_config.PLUGINS_CONFIG_KEY: []}
+        plugins_v0.DictPlugin({"name": "plugin1"})
+        plugins_v0.DictPlugin({"name": "plugin2"})
+        plugins.load("plugin2")
+        plugins.load("plugin1")
+        tutor_config.save_enabled_plugins(config)
+        self.assertEqual(
+            ["plugin1", "plugin2"], config[tutor_config.PLUGINS_CONFIG_KEY]
+        )
+
+    def test_enable_twice(self) -> None:
+        plugins_v0.DictPlugin({"name": "plugin1"})
+        plugins.load("plugin1")
+        plugins.load("plugin1")
+        config: Config = {tutor_config.PLUGINS_CONFIG_KEY: []}
+        tutor_config.save_enabled_plugins(config)
+        self.assertEqual(["plugin1"], config[tutor_config.PLUGINS_CONFIG_KEY])
+
+    def test_load_not_installed_plugin(self) -> None:
+        self.assertRaises(exceptions.TutorError, plugins.load, "plugin1")
+
+    def test_disable(self) -> None:
+        plugins_v0.DictPlugin(
+            {
+                "name": "plugin1",
+                "version": "1.0.0",
+                "config": {"set": {"KEY": "value"}},
+            }
+        )
+        plugins_v0.DictPlugin(
+            {
+                "name": "plugin2",
+                "version": "1.0.0",
+            }
+        )
+        config: Config = {"PLUGINS": ["plugin1", "plugin2"]}
+        tutor_config.enable_plugins(config)
+        with patch.object(fmt, "STDOUT"):
+            hooks.Actions.PLUGIN_UNLOADED.do("plugin1", "", config)
+        self.assertEqual(["plugin2"], config["PLUGINS"])
+
+    def test_disable_removes_set_config(self) -> None:
+        plugins_v0.DictPlugin(
+            {
+                "name": "plugin1",
+                "version": "1.0.0",
+                "config": {"set": {"KEY": "value"}},
+            }
+        )
+        config: Config = {"PLUGINS": ["plugin1"], "KEY": "value"}
+        tutor_config.enable_plugins(config)
+        with patch.object(fmt, "STDOUT"):
+            hooks.Actions.PLUGIN_UNLOADED.do("plugin1", "", config)
+        self.assertEqual([], config["PLUGINS"])
+        self.assertNotIn("KEY", config)
+
+    def test_patches(self) -> None:
+        plugins_v0.DictPlugin(
+            {"name": "plugin1", "patches": {"patch1": "Hello {{ ID }}"}}
+        )
+        plugins.load("plugin1")
+        patches = list(plugins.iter_patches("patch1"))
+        self.assertEqual(["Hello {{ ID }}"], patches)
+
+    def test_plugin_without_patches(self) -> None:
+        plugins_v0.DictPlugin({"name": "plugin1"})
+        plugins.load("plugin1")
+        patches = list(plugins.iter_patches("patch1"))
+        self.assertEqual([], patches)
+
+    def test_configure(self) -> None:
+        plugins_v0.DictPlugin(
+            {
+                "name": "plugin1",
+                "config": {
+                    "add": {"PARAM1": "value1", "PARAM2": "value2"},
+                    "set": {"PARAM3": "value3"},
+                    "defaults": {"PARAM4": "value4"},
+                },
+            }
+        )
+        plugins.load("plugin1")
+
+        base = tutor_config.get_base()
+        defaults = tutor_config.get_defaults()
+
+        self.assertEqual(base["PARAM3"], "value3")
+        self.assertEqual(base["PLUGIN1_PARAM1"], "value1")
+        self.assertEqual(base["PLUGIN1_PARAM2"], "value2")
+        self.assertEqual(defaults["PLUGIN1_PARAM4"], "value4")
+
+    def test_configure_set_does_not_override(self) -> None:
+        config: Config = {"ID1": "oldid"}
+
+        plugins_v0.DictPlugin(
+            {"name": "plugin1", "config": {"set": {"ID1": "newid", "ID2": "id2"}}}
+        )
+        plugins.load("plugin1")
+        tutor_config.update_with_base(config)
+
+        self.assertEqual("oldid", config["ID1"])
+        self.assertEqual("id2", config["ID2"])
+
+    def test_configure_set_random_string(self) -> None:
+        plugins_v0.DictPlugin(
+            {
+                "name": "plugin1",
+                "config": {"set": {"PARAM1": "{{ 128|random_string }}"}},
+            }
+        )
+        plugins.load("plugin1")
+        config = tutor_config.get_base()
+        tutor_config.render_full(config)
+
+        self.assertEqual(128, len(get_typed(config, "PARAM1", str)))
+
+    def test_configure_default_value_with_previous_definition(self) -> None:
+        config: Config = {"PARAM1": "value"}
+        plugins_v0.DictPlugin(
+            {"name": "plugin1", "config": {"defaults": {"PARAM2": "{{ PARAM1 }}"}}}
+        )
+        plugins.load("plugin1")
+        tutor_config.update_with_defaults(config)
+        self.assertEqual("{{ PARAM1 }}", config["PLUGIN1_PARAM2"])
+
+    def test_config_load_from_plugins(self) -> None:
+        config: Config = {}
+
+        plugins_v0.DictPlugin(
+            {"name": "plugin1", "config": {"add": {"PARAM1": "{{ 10|random_string }}"}}}
+        )
+        plugins.load("plugin1")
+
+        tutor_config.update_with_base(config)
+        tutor_config.update_with_defaults(config)
+        tutor_config.render_full(config)
+        value1 = get_typed(config, "PLUGIN1_PARAM1", str)
+
+        self.assertEqual(10, len(value1))
+
+    def test_init_tasks(self) -> None:
+        plugins_v0.DictPlugin({"name": "plugin1", "hooks": {"init": ["myclient"]}})
+        plugins.load("plugin1")
+        self.assertIn(
+            ("myclient", ("plugin1", "hooks", "myclient", "init")),
+            list(hooks.Filters.COMMANDS_INIT.iterate()),
+        )
+
+    def test_plugins_are_updated_on_config_change(self) -> None:
+        config: Config = {}
+        plugins_v0.DictPlugin({"name": "plugin1"})
+        tutor_config.enable_plugins(config)
+        plugins1 = list(plugins.iter_loaded())
+        config["PLUGINS"] = ["plugin1"]
+        tutor_config.enable_plugins(config)
+        plugins2 = list(plugins.iter_loaded())
+
+        self.assertEqual([], plugins1)
+        self.assertEqual(1, len(plugins2))
+
+    def test_dict_plugin(self) -> None:
+        plugin = plugins_v0.DictPlugin(
+            {"name": "myplugin", "config": {"set": {"KEY": "value"}}, "version": "0.1"}
+        )
+        plugins.load("myplugin")
+        overriden_items: t.List[
+            t.Tuple[str, t.Any]
+        ] = hooks.Filters.CONFIG_OVERRIDES.apply([])
+        versions = list(plugins.iter_info())
+        self.assertEqual("myplugin", plugin.name)
+        self.assertEqual([("myplugin", "0.1")], versions)
+        self.assertEqual([("KEY", "value")], overriden_items)
+
+    def test_config_disable_plugin(self) -> None:
+        plugins_v0.DictPlugin(
+            {"name": "plugin1", "config": {"set": {"KEY1": "value1"}}}
+        )
+        plugins_v0.DictPlugin(
+            {"name": "plugin2", "config": {"set": {"KEY2": "value2"}}}
+        )
+        plugins.load("plugin1")
+        plugins.load("plugin2")
+
+        with temporary_root() as root:
+            config = tutor_config.load_minimal(root)
+            config_pre = config.copy()
+            with patch.object(fmt, "STDOUT"):
+                hooks.Actions.PLUGIN_UNLOADED.do("plugin1", "", config)
+            config_post = tutor_config.load_minimal(root)
+
+        self.assertEqual("value1", config_pre["KEY1"])
+        self.assertEqual("value2", config_pre["KEY2"])
+        self.assertNotIn("KEY1", config)
+        self.assertNotIn("KEY1", config_post)
+        self.assertEqual("value2", config["KEY2"])

tutor.spec

@@ -11,7 +11,11 @@ hidden_imports = []
 # Auto-discover plugins and include patches & templates folders
 for entrypoint in pkg_resources.iter_entry_points("tutor.plugin.v0"):
     plugin_name = entrypoint.name
-    plugin = entrypoint.load()
+    try:
+        plugin = entrypoint.load()
+    except Exception as e:
+        print(f"ERROR Failed to load plugin {plugin_name}: {e}")
+        continue
     plugin_root = os.path.dirname(plugin.__file__)
     plugin_root_module_name = os.path.basename(plugin_root)
     hidden_imports.append(entrypoint.module_name)

tutor/commands/cli.py

@@ -1,39 +1,93 @@
 import sys
+import typing as t
 
 import appdirs
 import click
 
-from .. import exceptions, fmt, utils
-from ..__about__ import __app__, __version__
-from .config import config_command
-from .context import Context
-from .dev import dev
-from .images import images_command
-from .k8s import k8s
-from .local import local
-from .plugins import add_plugin_commands, plugins_command
+from tutor import exceptions, fmt, hooks, utils
+from tutor.__about__ import __app__, __version__
+from tutor.commands.config import config_command
+from tutor.commands.context import Context
+from tutor.commands.dev import dev
+from tutor.commands.images import images_command
+from tutor.commands.k8s import k8s
+from tutor.commands.local import local
+from tutor.commands.plugins import plugins_command
+
+# Everyone on board
+hooks.Actions.CORE_READY.do()
 
 
 def main() -> None:
     try:
-        cli.add_command(images_command)
-        cli.add_command(config_command)
-        cli.add_command(local)
-        cli.add_command(dev)
-        cli.add_command(k8s)
-        cli.add_command(print_help)
-        cli.add_command(plugins_command)
-        add_plugin_commands(cli)
         cli()  # pylint: disable=no-value-for-parameter
     except KeyboardInterrupt:
         pass
     except exceptions.TutorError as e:
-        fmt.echo_error("Error: {}".format(e.args[0]))
+        fmt.echo_error(f"Error: {e.args[0]}")
         sys.exit(1)
 
 
+class TutorCli(click.MultiCommand):
+    """
+    Dynamically load subcommands at runtime.
+
+    This is necessary to load plugin subcommands, based on the list of enabled
+    plugins (and thus of config.yml).
+    Docs: https://click.palletsprojects.com/en/latest/commands/#custom-multi-commands
+    """
+
+    IS_ROOT_READY = False
+
+    @classmethod
+    def iter_commands(cls, ctx: click.Context) -> t.Iterator[click.Command]:
+        """
+        Return the list of subcommands (click.Command).
+        """
+        cls.ensure_plugins_enabled(ctx)
+        yield from hooks.Filters.CLI_COMMANDS.iterate()
+
+    @classmethod
+    def ensure_plugins_enabled(cls, ctx: click.Context) -> None:
+        """
+        We enable plugins as soon as possible to have access to commands.
+        """
+        if not isinstance(ctx, click.Context):
+            # When generating docs, this function is incorrectly called with a
+            # multicommand object instead of a Context. That's ok, we just
+            # ignore it.
+            # https://github.com/click-contrib/sphinx-click/issues/70
+            return
+        if not cls.IS_ROOT_READY:
+            hooks.Actions.PROJECT_ROOT_READY.do(root=ctx.params["root"])
+            cls.IS_ROOT_READY = True
+
+    def list_commands(self, ctx: click.Context) -> t.List[str]:
+        """
+        This is run in the following cases:
+        - shell autocompletion: tutor <tab>
+        - print help: tutor, tutor -h
+        """
+        return sorted(
+            [command.name or "<undefined>" for command in self.iter_commands(ctx)]
+        )
+
+    def get_command(
+        self, ctx: click.Context, cmd_name: str
+    ) -> t.Optional[click.Command]:
+        """
+        This is run when passing a command from the CLI. E.g: tutor config ...
+        """
+        for command in self.iter_commands(ctx):
+            if cmd_name == command.name:
+                return command
+        return None
+
+
 @click.group(
-    context_settings={"help_option_names": ["-h", "--help", "help"]},
+    cls=TutorCli,
+    invoke_without_command=True,
+    add_help_option=False,  # Context is incorrectly loaded when help option is automatically added
     help="Tutor is the Docker-based Open edX distribution designed for peace of mind.",
 )
 @click.version_option(version=__version__)
@@ -46,8 +100,15 @@ def main() -> None:
     type=click.Path(resolve_path=True),
     help="Root project directory (environment variable: TUTOR_ROOT)",
 )
+@click.option(
+    "-h",
+    "--help",
+    "show_help",
+    is_flag=True,
+    help="Print this help",
+)
 @click.pass_context
-def cli(context: click.Context, root: str) -> None:
+def cli(context: click.Context, root: str, show_help: bool) -> None:
     if utils.is_root():
         fmt.echo_alert(
             "You are running Tutor as root. This is strongly not recommended. If you are doing this in order to access"
@@ -55,12 +116,28 @@ def cli(context: click.Context, root: str) -> None:
             "/install/linux/linux-postinstall/#manage-docker-as-a-non-root-user)"
         )
     context.obj = Context(root)
+    if context.invoked_subcommand is None or show_help:
+        click.echo(context.get_help())
 
 
 @click.command(help="Print this help", name="help")
-def print_help() -> None:
-    context = click.Context(cli)
-    click.echo(cli.get_help(context))
+@click.pass_context
+def help_command(context: click.Context) -> None:
+    context.invoke(cli, show_help=True)
+
+
+hooks.filters.add_items(
+    "cli:commands",
+    [
+        images_command,
+        config_command,
+        local,
+        dev,
+        k8s,
+        help_command,
+        plugins_command,
+    ],
+)
 
 
 if __name__ == "__main__":

tutor/commands/compose.py

@@ -3,13 +3,13 @@ from typing import List
 
 import click
 
-from .. import bindmounts
-from .. import config as tutor_config
-from .. import env as tutor_env
-from .. import fmt, jobs, utils
-from ..exceptions import TutorError
-from ..types import Config
-from .context import BaseJobContext
+from tutor import bindmounts
+from tutor import config as tutor_config
+from tutor import env as tutor_env
+from tutor import fmt, jobs, utils
+from tutor.commands.context import BaseJobContext
+from tutor.exceptions import TutorError
+from tutor.types import Config
 
 
 class ComposeJobRunner(jobs.BaseComposeJobRunner):

tutor/commands/config.py

@@ -80,10 +80,9 @@ def render(context: Context, extra_configs: List[str], src: str, dst: str) -> No
         config.update(
             env.render_unknown(config, tutor_config.get_yaml_file(extra_config))
         )
-
     renderer = env.Renderer(config, [src])
     renderer.render_all_to(dst)
-    fmt.echo_info("Templates rendered to {}".format(dst))
+    fmt.echo_info(f"Templates rendered to {dst}")
 
 
 @click.command(help="Print the project root")
@@ -101,9 +100,7 @@ def printvalue(context: Context, key: str) -> None:
         # Note that this will incorrectly print None values
         fmt.echo(str(config[key]))
     except KeyError as e:
-        raise exceptions.TutorError(
-            "Missing configuration value: {}".format(key)
-        ) from e
+        raise exceptions.TutorError(f"Missing configuration value: {key}") from e
 
 
 config_command.add_command(save)

tutor/commands/images.py

@@ -1,12 +1,12 @@
-from typing import Iterator, List, Tuple
+import typing as t
 
 import click
 
-from .. import config as tutor_config
-from .. import env as tutor_env
-from .. import exceptions, images, plugins
-from ..types import Config
-from .context import Context
+from tutor import config as tutor_config
+from tutor import env as tutor_env
+from tutor import exceptions, hooks, images
+from tutor.commands.context import Context
+from tutor.types import Config
 
 BASE_IMAGE_NAMES = ["openedx", "permissions"]
 VENDOR_IMAGES = [
@@ -19,6 +19,47 @@ VENDOR_IMAGES = [
 ]
 
 
+@hooks.Filters.IMAGES_BUILD.add()
+def _add_core_images_to_build(
+    build_images: t.List[t.Tuple[str, t.Tuple[str, str], str, t.List[str]]],
+    config: Config,
+) -> t.List[t.Tuple[str, t.Tuple[str, str], str, t.List[str]]]:
+    """
+    Add base images to the list of Docker images to build on `tutor build all`.
+    """
+    for image in BASE_IMAGE_NAMES:
+        tag = images.get_tag(config, image)
+        build_images.append((image, ("build", image), tag, []))
+    return build_images
+
+
+@hooks.Filters.IMAGES_PULL.add()
+def _add_images_to_pull(
+    remote_images: t.List[t.Tuple[str, str]], config: Config
+) -> t.List[t.Tuple[str, str]]:
+    """
+    Add base and vendor images to the list of Docker images to pull on `tutor pull all`.
+    """
+    for image in VENDOR_IMAGES:
+        if config.get(f"RUN_{image.upper()}", True):
+            remote_images.append((image, images.get_tag(config, image)))
+    for image in BASE_IMAGE_NAMES:
+        remote_images.append((image, images.get_tag(config, image)))
+    return remote_images
+
+
+@hooks.Filters.IMAGES_PULL.add()
+def _add_core_images_to_push(
+    remote_images: t.List[t.Tuple[str, str]], config: Config
+) -> t.List[t.Tuple[str, str]]:
+    """
+    Add base images to the list of Docker images to push on `tutor push all`.
+    """
+    for image in BASE_IMAGE_NAMES:
+        remote_images.append((image, images.get_tag(config, image)))
+    return remote_images
+
+
 @click.group(name="images", short_help="Manage docker images")
 def images_command() -> None:
     pass
@@ -59,12 +100,12 @@ def images_command() -> None:
 @click.pass_obj
 def build(
     context: Context,
-    image_names: List[str],
+    image_names: t.List[str],
     no_cache: bool,
-    build_args: List[str],
-    add_hosts: List[str],
+    build_args: t.List[str],
+    add_hosts: t.List[str],
     target: str,
-    docker_args: List[str],
+    docker_args: t.List[str],
 ) -> None:
     config = tutor_config.load(context.root)
     command_args = []
@@ -79,134 +120,92 @@ def build(
     if docker_args:
         command_args += docker_args
     for image in image_names:
-        build_image(context.root, config, image, *command_args)
+        for _name, path, tag, custom_args in find_images_to_build(config, image):
+            images.build(
+                tutor_env.pathjoin(context.root, *path),
+                tag,
+                *command_args,
+                *custom_args,
+            )
 
 
 @click.command(short_help="Pull images from the Docker registry")
 @click.argument("image_names", metavar="image", nargs=-1)
 @click.pass_obj
-def pull(context: Context, image_names: List[str]) -> None:
+def pull(context: Context, image_names: t.List[str]) -> None:
     config = tutor_config.load_full(context.root)
     for image in image_names:
-        pull_image(config, image)
+        for tag in find_remote_image_tags(config, hooks.Filters.IMAGES_PULL, image):
+            images.pull(tag)
 
 
 @click.command(short_help="Push images to the Docker registry")
 @click.argument("image_names", metavar="image", nargs=-1)
 @click.pass_obj
-def push(context: Context, image_names: List[str]) -> None:
+def push(context: Context, image_names: t.List[str]) -> None:
     config = tutor_config.load_full(context.root)
     for image in image_names:
-        push_image(config, image)
+        for tag in find_remote_image_tags(config, hooks.Filters.IMAGES_PUSH, image):
+            images.push(tag)
 
 
 @click.command(short_help="Print tag associated to a Docker image")
 @click.argument("image_names", metavar="image", nargs=-1)
 @click.pass_obj
-def printtag(context: Context, image_names: List[str]) -> None:
+def printtag(context: Context, image_names: t.List[str]) -> None:
     config = tutor_config.load_full(context.root)
     for image in image_names:
-        to_print = []
-        for _img, tag in iter_images(config, image, BASE_IMAGE_NAMES):
-            to_print.append(tag)
-        for _plugin, _img, tag in iter_plugin_images(config, image, "build-image"):
-            to_print.append(tag)
-
-        if not to_print:
-            raise ImageNotFoundError(image)
-
-        for tag in to_print:
+        for _name, _path, tag, _args in find_images_to_build(config, image):
             print(tag)
 
 
-def build_image(root: str, config: Config, image: str, *args: str) -> None:
-    to_build = []
+def find_images_to_build(
+    config: Config, image: str
+) -> t.Iterator[t.Tuple[str, t.Tuple[str], str, t.List[str]]]:
+    """
+    Iterate over all images to build.
 
-    # Build base images
-    for img, tag in iter_images(config, image, BASE_IMAGE_NAMES):
-        to_build.append((tutor_env.pathjoin(root, "build", img), tag, args))
+    If no corresponding image is found, raise exception.
 
-    # Build plugin images
-    for plugin, img, tag in iter_plugin_images(config, image, "build-image"):
-        to_build.append(
-            (tutor_env.pathjoin(root, "plugins", plugin, "build", img), tag, args)
-        )
+    Yield: (name, path, tag, build args)
+    """
+    all_images_to_build: t.Iterator[
+        t.Tuple[str, t.Tuple[str], str, t.List[str]]
+    ] = hooks.Filters.IMAGES_BUILD.iterate(config)
+    found = False
+    for name, path, tag, args in all_images_to_build:
+        if name == image or image == "all":
+            found = True
+            tag = tutor_env.render_str(config, tag)
+            yield (name, path, tag, args)
 
-    if not to_build:
+    if not found:
         raise ImageNotFoundError(image)
 
-    for path, tag, build_args in to_build:
-        images.build(path, tag, *args)
 
+def find_remote_image_tags(
+    config: Config, filtre: hooks.filters.Filter, image: str
+) -> t.Iterator[str]:
+    """
+    Iterate over all images to push or pull.
 
-def pull_image(config: Config, image: str) -> None:
-    to_pull = []
-    for _img, tag in iter_images(config, image, all_image_names(config)):
-        to_pull.append(tag)
-    for _plugin, _img, tag in iter_plugin_images(config, image, "remote-image"):
-        to_pull.append(tag)
+    If no corresponding image is found, raise exception.
 
-    if not to_pull:
+    Yield: tag
+    """
+    all_remote_images: t.Iterator[t.Tuple[str, str]] = filtre.iterate(config)
+    found = False
+    for name, tag in all_remote_images:
+        if name == image or image == "all":
+            found = True
+            yield tutor_env.render_str(config, tag)
+    if not found:
         raise ImageNotFoundError(image)
 
-    for tag in to_pull:
-        images.pull(tag)
-
-
-def push_image(config: Config, image: str) -> None:
-    to_push = []
-    for _img, tag in iter_images(config, image, BASE_IMAGE_NAMES):
-        to_push.append(tag)
-    for _plugin, _img, tag in iter_plugin_images(config, image, "remote-image"):
-        to_push.append(tag)
-
-    if not to_push:
-        raise ImageNotFoundError(image)
-
-    for tag in to_push:
-        images.push(tag)
-
-
-def iter_images(
-    config: Config, image: str, image_list: List[str]
-) -> Iterator[Tuple[str, str]]:
-    for img in image_list:
-        if image in [img, "all"]:
-            tag = images.get_tag(config, img)
-            yield img, tag
-
-
-def iter_plugin_images(
-    config: Config, image: str, hook_name: str
-) -> Iterator[Tuple[str, str, str]]:
-    for plugin, hook in plugins.iter_hooks(config, hook_name):
-        if not isinstance(hook, dict):
-            raise exceptions.TutorError(
-                "Invalid hook '{}': expected dict, got {}".format(
-                    hook_name, hook.__class__
-                )
-            )
-        for img, tag in hook.items():
-            if image in [img, "all"]:
-                tag = tutor_env.render_str(config, tag)
-                yield plugin, img, tag
-
-
-def all_image_names(config: Config) -> List[str]:
-    return BASE_IMAGE_NAMES + vendor_image_names(config)
-
-
-def vendor_image_names(config: Config) -> List[str]:
-    vendor_images = VENDOR_IMAGES[:]
-    for image in VENDOR_IMAGES:
-        if not config.get("RUN_" + image.upper(), True):
-            vendor_images.remove(image)
-    return vendor_images
-
 
 class ImageNotFoundError(exceptions.TutorError):
     def __init__(self, image_name: str):
-        super().__init__("Image '{}' could not be found".format(image_name))
+        super().__init__(f"Image '{image_name}' could not be found")
 
 
 images_command.add_command(build)

tutor/commands/plugins.py

@@ -1,13 +1,13 @@
 import os
-import shutil
 import urllib.request
-from typing import List
+import typing as t
 
 import click
 
-from .. import config as tutor_config
-from .. import env as tutor_env
-from .. import exceptions, fmt, plugins
+from tutor import config as tutor_config
+from tutor import exceptions, fmt, hooks, plugins
+from tutor.plugins.base import PLUGINS_ROOT, PLUGINS_ROOT_ENV_VAR_NAME
+
 from .context import Context
 
 
@@ -24,26 +24,29 @@ def plugins_command() -> None:
 
 
 @click.command(name="list", help="List installed plugins")
-@click.pass_obj
-def list_command(context: Context) -> None:
-    config = tutor_config.load_full(context.root)
-    for plugin in plugins.iter_installed():
-        status = "" if plugins.is_enabled(config, plugin.name) else " (disabled)"
-        print(
-            "{plugin}=={version}{status}".format(
-                plugin=plugin.name, status=status, version=plugin.version
-            )
-        )
+def list_command() -> None:
+    lines = []
+    first_column_width = 1
+    for plugin, plugin_info in plugins.iter_info():
+        plugin_info = plugin_info or ""
+        plugin_info.replace("\n", " ")
+        status = "" if plugins.is_loaded(plugin) else "(disabled)"
+        lines.append((plugin, status, plugin_info))
+        first_column_width = max([first_column_width, len(plugin) + 2])
+
+    for line in lines:
+        print("{:{width}}\t{:10}\t{}".format(*line, width=first_column_width))
 
 
 @click.command(help="Enable a plugin")
 @click.argument("plugin_names", metavar="plugin", nargs=-1)
 @click.pass_obj
-def enable(context: Context, plugin_names: List[str]) -> None:
+def enable(context: Context, plugin_names: t.List[str]) -> None:
     config = tutor_config.load_minimal(context.root)
     for plugin in plugin_names:
-        plugins.enable(config, plugin)
-        fmt.echo_info("Plugin {} enabled".format(plugin))
+        plugins.load(plugin)
+        fmt.echo_info(f"Plugin {plugin} enabled")
+    tutor_config.save_enabled_plugins(config)
     tutor_config.save_config_file(context.root, config)
     fmt.echo_info(
         "You should now re-generate your environment with `tutor config save`."
@@ -56,61 +59,43 @@ def enable(context: Context, plugin_names: List[str]) -> None:
 )
 @click.argument("plugin_names", metavar="plugin", nargs=-1)
 @click.pass_obj
-def disable(context: Context, plugin_names: List[str]) -> None:
+def disable(context: Context, plugin_names: t.List[str]) -> None:
     config = tutor_config.load_minimal(context.root)
     disable_all = "all" in plugin_names
-    for plugin in plugins.iter_enabled(config):
-        if disable_all or plugin.name in plugin_names:
-            fmt.echo_info("Disabling plugin {}...".format(plugin.name))
-            for key, value in plugin.config_set.items():
-                value = tutor_env.render_unknown(config, value)
-                fmt.echo_info("    Removing config entry {}={}".format(key, value))
-            plugins.disable(config, plugin)
-            delete_plugin(context.root, plugin.name)
-            fmt.echo_info("    Plugin disabled")
-    tutor_config.save_config_file(context.root, config)
-    fmt.echo_info(
-        "You should now re-generate your environment with `tutor config save`."
-    )
-
-
-def delete_plugin(root: str, name: str) -> None:
-    plugin_dir = tutor_env.pathjoin(root, "plugins", name)
-    if os.path.exists(plugin_dir):
-        try:
-            shutil.rmtree(plugin_dir)
-        except PermissionError as e:
-            raise exceptions.TutorError(
-                "Could not delete file {} from plugin {} in folder {}".format(
-                    e.filename, name, plugin_dir
-                )
-            )
+    disabled: t.List[str] = []
+    for plugin in tutor_config.get_enabled_plugins(config):
+        if disable_all or plugin in plugin_names:
+            fmt.echo_info(f"Disabling plugin {plugin}...")
+            hooks.Actions.PLUGIN_UNLOADED.do(plugin, context.root, config)
+            disabled.append(plugin)
+            fmt.echo_info(f"Plugin {plugin} disabled")
+    if disabled:
+        tutor_config.save_config_file(context.root, config)
+        fmt.echo_info(
+            "You should now re-generate your environment with `tutor config save`."
+        )
 
 
 @click.command(
     short_help="Print the location of yaml-based plugins",
-    help="""Print the location of yaml-based plugins. This location can be manually
-defined by setting the {} environment variable""".format(
-        plugins.DictPlugin.ROOT_ENV_VAR_NAME
-    ),
+    help=f"""Print the location of yaml-based plugins. This location can be manually
+defined by setting the {PLUGINS_ROOT_ENV_VAR_NAME} environment variable""",
 )
 def printroot() -> None:
-    fmt.echo(plugins.DictPlugin.ROOT)
+    fmt.echo(PLUGINS_ROOT)
 
 
 @click.command(
     short_help="Install a plugin",
-    help="""Install a plugin, either from a local YAML file or a remote, web-hosted
-location. The plugin will be installed to {}.""".format(
-        plugins.DictPlugin.ROOT_ENV_VAR_NAME
-    ),
+    help=f"""Install a plugin, either from a local Python/YAML file or a remote, web-hosted
+location. The plugin will be installed to {PLUGINS_ROOT_ENV_VAR_NAME}.""",
 )
 @click.argument("location")
 def install(location: str) -> None:
     basename = os.path.basename(location)
-    if not basename.endswith(".yml"):
-        basename += ".yml"
-    plugin_path = os.path.join(plugins.DictPlugin.ROOT, basename)
+    if not basename.endswith(".yml") and not basename.endswith(".py"):
+        basename += ".py"
+    plugin_path = os.path.join(PLUGINS_ROOT, basename)
 
     if location.startswith("http"):
         # Download file
@@ -118,28 +103,17 @@ def install(location: str) -> None:
         content = response.read().decode()
     elif os.path.isfile(location):
         # Read file
-        with open(location) as f:
+        with open(location, encoding="utf-8") as f:
             content = f.read()
     else:
-        raise exceptions.TutorError("No plugin found at {}".format(location))
+        raise exceptions.TutorError(f"No plugin found at {location}")
 
     # Save file
-    if not os.path.exists(plugins.DictPlugin.ROOT):
-        os.makedirs(plugins.DictPlugin.ROOT)
-    with open(plugin_path, "w", newline="\n") as f:
+    if not os.path.exists(PLUGINS_ROOT):
+        os.makedirs(PLUGINS_ROOT)
+    with open(plugin_path, "w", newline="\n", encoding="utf-8") as f:
         f.write(content)
-    fmt.echo_info("Plugin installed at {}".format(plugin_path))
-
-
-def add_plugin_commands(command_group: click.Group) -> None:
-    """
-    Add commands provided by all plugins to the given command group. Each command is
-    added with a name that is equal to the plugin name.
-    """
-    for plugin in plugins.iter_installed():
-        if isinstance(plugin.command, click.Command):
-            plugin.command.name = plugin.name
-            command_group.add_command(plugin.command)
+    fmt.echo_info(f"Plugin installed at {plugin_path}")
 
 
 plugins_command.add_command(list_command)

tutor/commands/upgrade/common.py

@@ -1,5 +1,5 @@
-from tutor import fmt
-from tutor import plugins
+from tutor import config as tutor_config
+from tutor import fmt, plugins
 from tutor.types import Config
 
 
@@ -9,23 +9,25 @@ def upgrade_from_lilac(config: Config) -> None:
             "The Open edX forum feature was moved to a separate plugin in Maple. To keep using this feature, "
             "you must install and enable the tutor-forum plugin: https://github.com/overhangio/tutor-forum"
         )
-    elif not plugins.is_enabled(config, "forum"):
+    elif not plugins.is_loaded("forum"):
         fmt.echo_info(
             "The Open edX forum feature was moved to a separate plugin in Maple. To keep using this feature, "
             "we will now enable the 'forum' plugin. If you do not want to use this feature, you should disable the "
             "plugin with: `tutor plugins disable forum`."
         )
-        plugins.enable(config, "forum")
+        plugins.load("forum")
+        tutor_config.save_enabled_plugins(config)
 
     if not plugins.is_installed("mfe"):
         fmt.echo_alert(
             "In Maple the legacy courseware is no longer supported. You need to install and enable the 'mfe' plugin "
             "to make use of the new learning microfrontend: https://github.com/overhangio/tutor-mfe"
         )
-    elif not plugins.is_enabled(config, "mfe"):
+    elif not plugins.is_loaded("mfe"):
         fmt.echo_info(
             "In Maple the legacy courseware is no longer supported. To start using the new learning microfrontend, "
             "we will now enable the 'mfe' plugin. If you do not want to use this feature, you should disable the "
             "plugin with: `tutor plugins disable mfe`."
         )
-        plugins.enable(config, "mfe")
+        plugins.load("mfe")
+        tutor_config.save_enabled_plugins(config)

tutor/commands/upgrade/k8s.py

@@ -3,6 +3,7 @@ from tutor import fmt
 from tutor.commands import k8s
 from tutor.commands.context import Context
 from tutor.types import Config
+
 from . import common as common_upgrade
 
 

tutor/commands/upgrade/local.py

@@ -7,6 +7,7 @@ from tutor import env as tutor_env
 from tutor import fmt
 from tutor.commands import compose
 from tutor.types import Config
+
 from . import common as common_upgrade
 
 

tutor/config.py

@@ -1,7 +1,8 @@
 import os
+import typing as t
 
-from . import env, exceptions, fmt, plugins, serialize, utils
-from .types import Config, cast_config
+from tutor import env, exceptions, fmt, hooks, plugins, serialize, utils
+from tutor.types import Config, ConfigValue, cast_config, get_typed
 
 CONFIG_FILENAME = "config.yml"
 
@@ -58,7 +59,7 @@ def update_with_base(config: Config) -> None:
 
     Note that configuration entries are unrendered at this point.
     """
-    base = get_base(config)
+    base = get_base()
     merge(config, base)
 
 
@@ -68,7 +69,7 @@ def update_with_defaults(config: Config) -> None:
 
     Note that configuration entries are unrendered at this point.
     """
-    defaults = get_defaults(config)
+    defaults = get_defaults()
     merge(config, defaults)
 
 
@@ -100,41 +101,37 @@ def get_user(root: str) -> Config:
     return config
 
 
-def get_base(config: Config) -> Config:
+def get_base() -> Config:
     """
     Load the base configuration.
 
     Entries in this configuration are unrendered.
     """
     base = get_template("base.yml")
-
-    # Load base values from plugins
-    for plugin in plugins.iter_enabled(config):
-        # Add new config key/values
-        for key, value in plugin.config_add.items():
-            new_key = plugin.config_key(key)
-            base[new_key] = value
-
-        # Set existing config key/values
-        for key, value in plugin.config_set.items():
-            base[key] = value
-
+    extra_config: t.List[t.Tuple[str, ConfigValue]] = []
+    extra_config = hooks.Filters.CONFIG_UNIQUE.apply(extra_config)
+    extra_config = hooks.Filters.CONFIG_OVERRIDES.apply(extra_config)
+    for name, value in extra_config:
+        if name in base:
+            fmt.echo_alert(
+                f"Found conflicting values for setting '{name}': '{value}' or '{base[name]}'"
+            )
+        base[name] = value
     return base
 
 
-def get_defaults(config: Config) -> Config:
+def get_defaults() -> Config:
     """
     Get default configuration, including from plugins.
 
     Entries in this configuration are unrendered.
     """
     defaults = get_template("defaults.yml")
-
-    for plugin in plugins.iter_enabled(config):
-        # Create new defaults
-        for key, value in plugin.config_defaults.items():
-            defaults[plugin.config_key(key)] = value
-
+    extra_defaults: t.Iterator[
+        t.Tuple[str, ConfigValue]
+    ] = hooks.Filters.CONFIG_DEFAULTS.iterate()
+    for name, value in extra_defaults:
+        defaults[name] = value
     update_with_env(defaults)
     return defaults
 
@@ -153,7 +150,7 @@ def get_yaml_file(path: str) -> Config:
     """
     Load config from yaml file.
     """
-    with open(path) as f:
+    with open(path, encoding="utf-8") as f:
         config = serialize.load(f.read())
     return cast_config(config)
 
@@ -198,11 +195,13 @@ def upgrade_obsolete(config: Config) -> None:
         config["OPENEDX_MYSQL_USERNAME"] = config.pop("MYSQL_USERNAME")
     if "RUN_NOTES" in config:
         if config["RUN_NOTES"]:
-            plugins.enable(config, "notes")
+            plugins.load("notes")
+            save_enabled_plugins(config)
         config.pop("RUN_NOTES")
     if "RUN_XQUEUE" in config:
         if config["RUN_XQUEUE"]:
-            plugins.enable(config, "xqueue")
+            plugins.load("xqueue")
+            save_enabled_plugins(config)
         config.pop("RUN_XQUEUE")
     if "SECRET_KEY" in config:
         config["OPENEDX_SECRET_KEY"] = config.pop("SECRET_KEY")
@@ -254,10 +253,73 @@ def convert_json2yml(root: str) -> None:
 def save_config_file(root: str, config: Config) -> None:
     path = config_path(root)
     utils.ensure_file_directory_exists(path)
-    with open(path, "w") as of:
+    with open(path, "w", encoding="utf-8") as of:
         serialize.dump(config, of)
     fmt.echo_info(f"Configuration saved to {path}")
 
 
 def config_path(root: str) -> str:
     return os.path.join(root, CONFIG_FILENAME)
+
+
+# Key name under which plugins are listed
+PLUGINS_CONFIG_KEY = "PLUGINS"
+
+
+def enable_plugins(config: Config) -> None:
+    """
+    Enable all plugins listed in the configuration.
+    """
+    plugins.load_all(get_enabled_plugins(config))
+
+
+def get_enabled_plugins(config: Config) -> t.List[str]:
+    """
+    Return the list of plugins that are enabled, as per the configuration. Note that
+    this may differ from the list of loaded plugins. For instance when a plugin is
+    present in the configuration but it's not installed.
+    """
+    return get_typed(config, PLUGINS_CONFIG_KEY, list, [])
+
+
+def save_enabled_plugins(config: Config) -> None:
+    """
+    Save the list of enabled plugins.
+
+    Plugins are deduplicated by name.
+    """
+    config[PLUGINS_CONFIG_KEY] = list(plugins.iter_loaded())
+
+
+@hooks.Actions.PROJECT_ROOT_READY.add()
+def _enable_plugins(root: str) -> None:
+    """
+    Enable plugins that are listed in the user configuration.
+    """
+    config = load_minimal(root)
+    enable_plugins(config)
+
+
+@hooks.Actions.PLUGIN_UNLOADED.add()
+def _remove_plugin_config_overrides_on_unload(
+    plugin: str, _root: str, config: Config
+) -> None:
+    # Find the configuration entries that were overridden by the plugin and
+    # remove them from the current config
+    overriden_config_items: t.Iterator[
+        t.Tuple[str, ConfigValue]
+    ] = hooks.Filters.CONFIG_OVERRIDES.iterate(context=hooks.Contexts.APP(plugin).name)
+    for key, _value in overriden_config_items:
+        value = config.pop(key, None)
+        value = env.render_unknown(config, value)
+        fmt.echo_info(f"    config - removing entry: {key}={value}")
+
+
+@hooks.Actions.PLUGIN_UNLOADED.add(priority=100)
+def _update_enabled_plugins_on_unload(_plugin: str, _root: str, config: Config) -> None:
+    """
+    Update the list of enabled plugins.
+
+    Note that this action must be performed after the plugin has been unloaded, hence the low priority.
+    """
+    save_enabled_plugins(config)

tutor/env.py

@@ -1,91 +1,136 @@
 import os
+import shutil
+import typing as t
 from copy import deepcopy
-from typing import Any, Iterable, List, Optional, Type, Union
 
 import jinja2
 import pkg_resources
 
-from . import exceptions, fmt, plugins, utils
-from .__about__ import __app__, __version__
-from .types import Config, ConfigValue
+from tutor import exceptions, fmt, hooks, plugins, utils
+from tutor.__about__ import __app__, __version__
+from tutor.types import Config, ConfigValue
 
 TEMPLATES_ROOT = pkg_resources.resource_filename("tutor", "templates")
 VERSION_FILENAME = "version"
 BIN_FILE_EXTENSIONS = [".ico", ".jpg", ".patch", ".png", ".ttf", ".woff", ".woff2"]
+JinjaFilter = t.Callable[..., t.Any]
+
+
+def _prepare_environment() -> None:
+    """
+    Prepare environment by adding core data to filters.
+    """
+    # Core template targets
+    hooks.Filters.ENV_TEMPLATE_TARGETS.add_items(
+        [
+            ("apps/", ""),
+            ("build/", ""),
+            ("dev/", ""),
+            ("k8s/", ""),
+            ("local/", ""),
+            (VERSION_FILENAME, ""),
+            ("kustomization.yml", ""),
+        ],
+    )
+    # Template filters
+    hooks.Filters.ENV_TEMPLATE_FILTERS.add_items(
+        [
+            ("common_domain", utils.common_domain),
+            ("encrypt", utils.encrypt),
+            ("list_if", utils.list_if),
+            ("long_to_base64", utils.long_to_base64),
+            ("random_string", utils.random_string),
+            ("reverse_host", utils.reverse_host),
+            ("rsa_private_key", utils.rsa_private_key),
+        ],
+    )
+    # Template variables
+    hooks.Filters.ENV_TEMPLATE_VARIABLES.add_items(
+        [
+            ("rsa_import_key", utils.rsa_import_key),
+            ("HOST_USER_ID", utils.get_user_id()),
+            ("TUTOR_APP", __app__.replace("-", "_")),
+            ("TUTOR_VERSION", __version__),
+        ],
+    )
+
+
+_prepare_environment()
 
 
 class JinjaEnvironment(jinja2.Environment):
     loader: jinja2.BaseLoader
 
-    def __init__(self, template_roots: List[str]) -> None:
+    def __init__(self, template_roots: t.List[str]) -> None:
         loader = jinja2.FileSystemLoader(template_roots)
         super().__init__(loader=loader, undefined=jinja2.StrictUndefined)
 
 
 class Renderer:
     @classmethod
-    def instance(cls: Type["Renderer"], config: Config) -> "Renderer":
+    def instance(cls: t.Type["Renderer"], config: Config) -> "Renderer":
         # Load template roots: these are required to be able to use
         # {% include .. %} directives
-        template_roots = [TEMPLATES_ROOT]
-        for plugin in plugins.iter_enabled(config):
-            if plugin.templates_root:
-                template_roots.append(plugin.templates_root)
-
+        template_roots = hooks.Filters.ENV_TEMPLATE_ROOTS.apply([TEMPLATES_ROOT])
         return cls(config, template_roots, ignore_folders=["partials"])
 
     def __init__(
         self,
         config: Config,
-        template_roots: List[str],
-        ignore_folders: Optional[List[str]] = None,
+        template_roots: t.List[str],
+        ignore_folders: t.Optional[t.List[str]] = None,
     ):
         self.config = deepcopy(config)
         self.template_roots = template_roots
         self.ignore_folders = ignore_folders or []
         self.ignore_folders.append(".git")
 
-        # Create environment
-        environment = JinjaEnvironment(template_roots)
-        environment.filters["common_domain"] = utils.common_domain
-        environment.filters["encrypt"] = utils.encrypt
-        environment.filters["list_if"] = utils.list_if
-        environment.filters["long_to_base64"] = utils.long_to_base64
-        environment.globals["iter_values_named"] = self.iter_values_named
-        environment.globals["patch"] = self.patch
-        environment.filters["random_string"] = utils.random_string
-        environment.filters["reverse_host"] = utils.reverse_host
-        environment.globals["rsa_import_key"] = utils.rsa_import_key
-        environment.filters["rsa_private_key"] = utils.rsa_private_key
-        environment.filters["walk_templates"] = self.walk_templates
-        environment.globals["HOST_USER_ID"] = utils.get_user_id()
-        environment.globals["TUTOR_APP"] = __app__.replace("-", "_")
-        environment.globals["TUTOR_VERSION"] = __version__
-        self.environment = environment
+        # Create environment with extra filters and globals
+        self.environment = JinjaEnvironment(template_roots)
 
-    def iter_templates_in(self, *prefix: str) -> Iterable[str]:
+        # Filters
+        plugin_filters: t.Iterator[
+            t.Tuple[str, JinjaFilter]
+        ] = hooks.Filters.ENV_TEMPLATE_FILTERS.iterate()
+        for name, func in plugin_filters:
+            if name in self.environment.filters:
+                fmt.echo_alert(f"Found conflicting template filters named '{name}'")
+            self.environment.filters[name] = func
+        self.environment.filters["walk_templates"] = self.walk_templates
+
+        # Globals
+        plugin_globals: t.Iterator[
+            t.Tuple[str, JinjaFilter]
+        ] = hooks.Filters.ENV_TEMPLATE_VARIABLES.iterate()
+        for name, value in plugin_globals:
+            if name in self.environment.globals:
+                fmt.echo_alert(f"Found conflicting template variables named '{name}'")
+            self.environment.globals[name] = value
+        self.environment.globals["iter_values_named"] = self.iter_values_named
+        self.environment.globals["patch"] = self.patch
+
+    def iter_templates_in(self, *prefix: str) -> t.Iterable[str]:
         """
         The elements of `prefix` must contain only "/", and not os.sep.
         """
         full_prefix = "/".join(prefix)
-        env_templates: List[str] = self.environment.loader.list_templates()
+        env_templates: t.List[str] = self.environment.loader.list_templates()
         for template in env_templates:
             if template.startswith(full_prefix) and self.is_part_of_env(template):
                 yield template
 
     def iter_values_named(
         self,
-        prefix: Optional[str] = None,
-        suffix: Optional[str] = None,
+        prefix: t.Optional[str] = None,
+        suffix: t.Optional[str] = None,
         allow_empty: bool = False,
-    ) -> Iterable[ConfigValue]:
+    ) -> t.Iterable[ConfigValue]:
         """
         Iterate on all config values for which the name match the given pattern.
 
         Note that here we only iterate on the values, not the key names. Empty
         values (those that evaluate to boolean `false`) will not be yielded, unless
         `allow_empty` is True.
-        TODO document this in the plugins API
         """
         for var_name, value in self.config.items():
             if prefix is not None and not var_name.startswith(prefix):
@@ -96,7 +141,7 @@ class Renderer:
                 continue
             yield value
 
-    def walk_templates(self, subdir: str) -> Iterable[str]:
+    def walk_templates(self, subdir: str) -> t.Iterable[str]:
         """
         Iterate on the template files from `templates/<subdir>`.
 
@@ -134,11 +179,11 @@ class Renderer:
         Render calls to {{ patch("...") }} in environment templates from plugin patches.
         """
         patches = []
-        for plugin, patch in plugins.iter_patches(self.config, name):
+        for patch in plugins.iter_patches(name):
             try:
                 patches.append(self.render_str(patch))
             except exceptions.TutorError:
-                fmt.echo_error(f"Error rendering patch '{name}' from plugin {plugin}")
+                fmt.echo_error(f"Error rendering patch '{name}': {patch}")
                 raise
         rendered = separator.join(patches)
         if rendered:
@@ -149,7 +194,7 @@ class Renderer:
         template = self.environment.from_string(text)
         return self.__render(template)
 
-    def render_template(self, template_name: str) -> Union[str, bytes]:
+    def render_template(self, template_name: str) -> t.Union[str, bytes]:
         """
         Render a template file. Return the corresponding string. If it's a binary file
         (as indicated by its path), return bytes.
@@ -177,14 +222,14 @@ class Renderer:
             fmt.echo_error("Unknown error rendering template " + template_name)
             raise
 
-    def render_all_to(self, root: str, *prefix: str) -> None:
+    def render_all_to(self, dst: str, *prefix: str) -> None:
         """
         `prefix` can be used to limit the templates to render.
         """
         for template_name in self.iter_templates_in(*prefix):
             rendered = self.render_template(template_name)
-            dst = os.path.join(root, template_name.replace("/", os.sep))
-            write_to(rendered, dst)
+            template_dst = os.path.join(dst, template_name.replace("/", os.sep))
+            write_to(rendered, template_dst)
 
     def __render(self, template: jinja2.Template) -> str:
         try:
@@ -198,20 +243,11 @@ def save(root: str, config: Config) -> None:
     Save the full environment, including version information.
     """
     root_env = pathjoin(root)
-    for prefix in [
-        "apps/",
-        "build/",
-        "dev/",
-        "k8s/",
-        "local/",
-        VERSION_FILENAME,
-        "kustomization.yml",
-    ]:
-        save_all_from(prefix, root_env, config)
-
-    for plugin in plugins.iter_enabled(config):
-        if plugin.templates_root:
-            save_plugin_templates(plugin, root, config)
+    targets: t.Iterator[
+        t.Tuple[str, str]
+    ] = hooks.Filters.ENV_TEMPLATE_TARGETS.iterate()
+    for src, dst in targets:
+        save_all_from(src, os.path.join(root_env, dst), config)
 
     upgrade_obsolete(root)
     fmt.echo_info(f"Environment generated in {base_dir(root)}")
@@ -223,29 +259,16 @@ def upgrade_obsolete(_root: str) -> None:
     """
 
 
-def save_plugin_templates(
-    plugin: plugins.BasePlugin, root: str, config: Config
-) -> None:
-    """
-    Save plugin templates to plugins/<plugin name>/*.
-    Only the "apps" and "build" subfolders are rendered.
-    """
-    plugins_root = pathjoin(root, "plugins")
-    for subdir in ["apps", "build"]:
-        subdir_path = os.path.join(plugin.name, subdir)
-        save_all_from(subdir_path, plugins_root, config)
-
-
-def save_all_from(prefix: str, root: str, config: Config) -> None:
+def save_all_from(prefix: str, dst: str, config: Config) -> None:
     """
     Render the templates that start with `prefix` and store them with the same
-    hierarchy at `root`. Here, `prefix` can be the result of os.path.join(...).
+    hierarchy at `dst`. Here, `prefix` can be the result of os.path.join(...).
     """
     renderer = Renderer.instance(config)
-    renderer.render_all_to(root, prefix.replace(os.sep, "/"))
+    renderer.render_all_to(dst, prefix.replace(os.sep, "/"))
 
 
-def write_to(content: Union[str, bytes], path: str) -> None:
+def write_to(content: t.Union[str, bytes], path: str) -> None:
     """
     Write some content to a path. Content can be either str or bytes.
     """
@@ -258,7 +281,7 @@ def write_to(content: Union[str, bytes], path: str) -> None:
             of_text.write(content)
 
 
-def render_file(config: Config, *path: str) -> Union[str, bytes]:
+def render_file(config: Config, *path: str) -> t.Union[str, bytes]:
     """
     Return the rendered contents of a template.
     """
@@ -267,7 +290,7 @@ def render_file(config: Config, *path: str) -> Union[str, bytes]:
     return renderer.render_template(template_name)
 
 
-def render_unknown(config: Config, value: Any) -> Any:
+def render_unknown(config: Config, value: t.Any) -> t.Any:
     """
     Render an unknown `value` object with the selected config.
 
@@ -311,7 +334,7 @@ def is_up_to_date(root: str) -> bool:
     return current is None or current == __version__
 
 
-def should_upgrade_from_release(root: str) -> Optional[str]:
+def should_upgrade_from_release(root: str) -> t.Optional[str]:
     """
     Return the name of the currently installed release that we should upgrade from. Return None If we already run the
     latest release.
@@ -326,7 +349,7 @@ def should_upgrade_from_release(root: str) -> Optional[str]:
     return get_release(current)
 
 
-def get_env_release(root: str) -> Optional[str]:
+def get_env_release(root: str) -> t.Optional[str]:
     """
     Return the Open edX release name from the current environment.
 
@@ -356,7 +379,7 @@ def get_release(version: str) -> str:
     }[version.split(".", maxsplit=1)[0]]
 
 
-def current_version(root: str) -> Optional[str]:
+def current_version(root: str) -> t.Optional[str]:
     """
     Return the current environment version. If the current environment has no version,
     return None.
@@ -415,3 +438,23 @@ def root_dir(root: str) -> str:
     Return the project root directory.
     """
     return os.path.abspath(root)
+
+
+@hooks.Actions.PLUGIN_UNLOADED.add()
+def _delete_plugin_templates(plugin: str, root: str, _config: Config) -> None:
+    """
+    Delete plugin env files on unload.
+    """
+    targets: t.Iterator[t.Tuple[str, str]] = hooks.Filters.ENV_TEMPLATE_TARGETS.iterate(
+        context=hooks.Contexts.APP(plugin).name
+    )
+    for src, dst in targets:
+        path = pathjoin(root, dst.replace("/", os.sep), src.replace("/", os.sep))
+        if os.path.exists(path):
+            fmt.echo_info(f"    env - removing folder: {path}")
+            try:
+                shutil.rmtree(path)
+            except PermissionError as e:
+                raise exceptions.TutorError(
+                    f"Could not delete file {e.filename} from plugin {plugin} in folder {path}"
+                )

tutor/hooks/__init__.py

@@ -0,0 +1,16 @@
+# The Tutor plugin system is licensed under the terms of the Apache 2.0 license.
+__license__ = "Apache 2.0"
+
+import typing as t
+
+# These imports are the hooks API
+from . import actions, contexts, filters
+from .consts import *
+
+
+def clear_all(context: t.Optional[str] = None) -> None:
+    """
+    Clear both actions and filters.
+    """
+    filters.clear_all(context=context)
+    actions.clear_all(context=context)

tutor/hooks/actions.py

@@ -0,0 +1,209 @@
+# The Tutor plugin system is licensed under the terms of the Apache 2.0 license.
+__license__ = "Apache 2.0"
+
+import sys
+import typing as t
+
+from .contexts import Contextualized
+
+# Similarly to CallableFilter, it should be possible to refine the definition of
+# CallableAction in the future.
+CallableAction = t.Callable[..., None]
+
+DEFAULT_PRIORITY = 10
+
+
+class ActionCallback(Contextualized):
+    def __init__(
+        self,
+        func: CallableAction,
+        priority: t.Optional[int] = None,
+    ):
+        super().__init__()
+        self.func = func
+        self.priority = priority or DEFAULT_PRIORITY
+
+    def do(
+        self, *args: t.Any, context: t.Optional[str] = None, **kwargs: t.Any
+    ) -> None:
+        if self.is_in_context(context):
+            self.func(*args, **kwargs)
+
+
+class Action:
+    """
+    Each action is associated to a name and a list of callbacks, sorted by
+    priority.
+    """
+
+    INDEX: t.Dict[str, "Action"] = {}
+
+    def __init__(self, name: str) -> None:
+        self.name = name
+        self.callbacks: t.List[ActionCallback] = []
+
+    def __repr__(self) -> str:
+        return f"{self.__class__.__name__}('{self.name}')"
+
+    @classmethod
+    def get(cls, name: str) -> "Action":
+        """
+        Get an existing action with the given name from the index, or create one.
+        """
+        return cls.INDEX.setdefault(name, cls(name))
+
+    def add(
+        self, priority: t.Optional[int] = None
+    ) -> t.Callable[[CallableAction], CallableAction]:
+        def inner(func: CallableAction) -> CallableAction:
+            callback = ActionCallback(func, priority=priority)
+            # I wish we could use bisect.insort_right here but the `key=` parameter
+            # is unsupported in Python 3.9
+            position = 0
+            while (
+                position < len(self.callbacks)
+                and self.callbacks[position].priority <= callback.priority
+            ):
+                position += 1
+            self.callbacks.insert(position, callback)
+            return func
+
+        return inner
+
+    def do(
+        self, *args: t.Any, context: t.Optional[str] = None, **kwargs: t.Any
+    ) -> None:
+        for callback in self.callbacks:
+            try:
+                callback.do(*args, context=context, **kwargs)
+            except:
+                sys.stderr.write(
+                    f"Error applying action '{self.name}': func={callback.func} contexts={callback.contexts}'\n"
+                )
+                raise
+
+    def clear(self, context: t.Optional[str] = None) -> None:
+        self.callbacks = [
+            callback
+            for callback in self.callbacks
+            if not callback.is_in_context(context)
+        ]
+
+
+class ActionTemplate:
+    """
+    Action templates are for actions for which the name needs to be formatted
+    before the action can be applied.
+    """
+
+    def __init__(self, name: str):
+        self.template = name
+
+    def __repr__(self) -> str:
+        return f"{self.__class__.__name__}('{self.template}')"
+
+    def __call__(self, *args: t.Any, **kwargs: t.Any) -> Action:
+        return get(self.template.format(*args, **kwargs))
+
+
+# Syntactic sugar
+get = Action.get
+
+
+def get_template(name: str) -> ActionTemplate:
+    """
+    Create an action with a template name.
+
+    Templated actions must be formatted with ``(*args)`` before being applied. For example::
+
+        action_template = actions.get_template("namespace:{0}")
+
+        @action_template("name").add()
+        def my_callback():
+            ...
+
+        action_template("name").do()
+    """
+    return ActionTemplate(name)
+
+
+def add(
+    name: str,
+    priority: t.Optional[int] = None,
+) -> t.Callable[[CallableAction], CallableAction]:
+    """
+    Decorator to add a callback action associated to a name.
+
+    :param name: name of the action. For forward compatibility, it is
+        recommended not to hardcode any string here, but to pick a value from
+        :py:class:`tutor.hooks.Actions` instead.
+    :param priority: optional order in which the action callbacks are performed. Higher
+        values mean that they will be performed later. The default value is
+        ``DEFAULT_PRIORITY`` (10). Actions that should be performed last should
+        have a priority of 100.
+
+    Usage::
+
+        from tutor import hooks
+
+        @hooks.actions.add("my-action")
+        def do_stuff():
+            ...
+
+    The ``do_stuff`` callback function will be called on ``hooks.actions.do("my-action")``. (see :py:func:`do`)
+
+    The signature of each callback action function must match the signature of the corresponding ``hooks.actions.do`` call. Callback action functions are not supposed to return any value. Returned values will be ignored.
+    """
+    return get(name).add(priority=priority)
+
+
+def do(
+    name: str, *args: t.Any, context: t.Optional[str] = None, **kwargs: t.Any
+) -> None:
+    """
+    Run action callbacks associated to a name/context.
+
+    :param name: name of the action for which callbacks will be run.
+    :param context: limit the set of callback actions to those that
+        were declared within a certain context (see
+        :py:func:`tutor.hooks.contexts.enter`).
+
+    Extra ``*args`` and ``*kwargs`` arguments will be passed as-is to
+    callback functions.
+
+    Callbacks are executed in order of priority, then FIFO. There is no error
+    management here: a single exception will cause all following callbacks
+    not to be run and the exception to be bubbled up.
+    """
+    action = Action.INDEX.get(name)
+    if action:
+        action.do(*args, context=context, **kwargs)
+
+
+def clear_all(context: t.Optional[str] = None) -> None:
+    """
+    Clear any previously defined filter with the  given context.
+
+    This will call :py:func:`clear` with all action names.
+    """
+    for name in Action.INDEX:
+        clear(name, context=context)
+
+
+def clear(name: str, context: t.Optional[str] = None) -> None:
+    """
+    Clear any previously defined action with the given name and context.
+
+    :param name: name of the action callbacks to remove.
+    :param context: when defined, will clear only the actions that were
+        created within that context.
+
+    Actions will be removed from the list of callbacks and will no longer be
+    run in :py:func:`do` calls.
+
+    This function should almost certainly never be called by plugins. It is
+    mostly useful to disable some plugins at runtime or in unit tests.
+    """
+    action = Action.INDEX.get(name)
+    if action:
+        action.clear(context=context)

tutor/hooks/consts.py

@@ -0,0 +1,287 @@
+"""
+List of all the action, filter and context names used across Tutor. This module is used
+to generate part of the reference documentation.
+"""
+# The Tutor plugin system is licensed under the terms of the Apache 2.0 license.
+__license__ = "Apache 2.0"
+
+from . import actions, contexts, filters
+
+__all__ = ["Actions", "Filters", "Contexts"]
+
+
+class Actions:
+    """
+    This class is a container for the names of all actions used across Tutor
+    (see :py:mod:`tutor.hooks.actions.do`). For each action, we describe the
+    arguments that are passed to the callback functions.
+
+    To create a new callback for an existing action, write the following::
+
+        from tutor import hooks
+
+        @hooks.Actions.YOUR_ACTION.add()
+        def your_action():
+            # Do stuff here
+    """
+
+    #: Called whenever the core project is ready to run. This action is called as soon
+    #: as possible. This is the right time to discover plugins, for instance. In
+    #: particular, we auto-discover the following plugins:
+    #:
+    #: - Python packages that declare a "tutor.plugin.v0" entrypoint.
+    #: - Python packages that declare a "tutor.plugin.v1" entrypoint.
+    #: - YAML and Python plugins stored in ~/.local/share/tutor-plugins (as indicated by ``tutor plugins printroot``)
+    #: - When running the binary version of Tutor, official plugins that ship with the binary are automatically discovered.
+    #:
+    #: Discovering a plugin is typically done by the Tutor plugin mechanism. Thus, plugin
+    #: developers probably don't have to implement this action themselves.
+    #:
+    #: This action does not have any parameter.
+    CORE_READY = actions.get("core:ready")
+
+    #: Called as soon as we have access to the Tutor project root.
+    #:
+    #: :parameter str root: absolute path to the project root.
+    PROJECT_ROOT_READY = actions.get("project:root:ready")
+
+    #: Triggered when a single plugin needs to be loaded. Only plugins that have previously been
+    #: discovered can be loaded (see :py:data:`CORE_READY`).
+    #:
+    #: Plugins are typically loaded because they were enabled by the user; the list of
+    #: plugins to enable is found in the project root (see
+    #: :py:data:``PROJECT_ROOT_READY``).
+    #:
+    #: Most plugin developers will not have to implement this action themselves, unless
+    #: they want to perform a specific action at the moment the plugin is enabled.
+    #:
+    #: This action does not have any parameter.
+    PLUGIN_LOADED = actions.get_template("plugins:loaded:{0}")
+
+    #: Triggered after all plugins have been loaded. At this point the list of loaded
+    #: plugins may be obtained from the :py:data:``Filters.PLUGINS_LOADED`` filter.
+    #:
+    #: This action does not have any parameter.
+    PLUGINS_LOADED = actions.get("plugins:loaded")
+
+    #: Triggered when a single plugin is unloaded. Only plugins that have previously been
+    #: loaded can be unloaded (see :py:data:`PLUGIN_LOADED`).
+    #:
+    #: Plugins are typically unloaded because they were disabled by the user.
+    #:
+    #: Most plugin developers will not have to implement this action themselves, unless
+    #: they want to perform a specific action at the moment the plugin is disabled.
+    #:
+    #: :parameter str plugin: plugin name.
+    #: :parameter str root: absolute path to the project root.
+    #: :parameter dict config: full project configuration
+    PLUGIN_UNLOADED = actions.get("plugins:unloaded")
+
+
+class Filters:
+    """
+    Here are the names of all filters used across Tutor. For each filter, the
+    type of the first argument also indicates the type of the expected returned value.
+
+    Filter names are all namespaced with domains separated by colons (":").
+
+    To add custom data to any filter, write the following in your plugin::
+
+        from tutor import hooks
+
+        @hooks.Filters.YOUR_FILTER.add()
+        def your_filter(items):
+            # do stuff with items
+            ...
+            # return the modified list of items
+            return items
+    """
+
+    #: List of images to be built when we run ``tutor images build ...``.
+    #:
+    #: :parameter list[tuple[str, tuple[str, ...], str, tuple[str, ...]]] tasks: list of ``(name, path, tag, args)`` tuples.
+    #:
+    #:    - ``name`` is the name of the image, as in ``tutor images build myimage``.
+    #:    - ``path`` is the relative path to the folder that contains the Dockerfile.
+    #:      For instance ``("myplugin", "build", "myservice")`` indicates that the template will be read from
+    #:      ``myplugin/build/myservice/Dockerfile``
+    #:    - ``tag`` is the Docker tag that will be applied to the image. It will be
+    #:      rendered at runtime with the user configuration. Thus, the image tag could
+    #:      be ``"{{ DOCKER_REGISTRY }}/myimage:{{ TUTOR_VERSION }}"``.
+    #:    - ``args`` is a list of arguments that will be passed to ``docker build ...``.
+    #: :parameter dict config: user configuration.
+    IMAGES_BUILD = filters.get("images:build")
+
+    #: List of images to be pulled when we run ``tutor images pull ...``.
+    #:
+    #: :parameter list[tuple[str, str]] tasks: list of ``(name, tag)`` tuples.
+    #:
+    #:    - ``name`` is the name of the image, as in ``tutor images pull myimage``.
+    #:    - ``tag`` is the Docker tag that will be applied to the image. (see :py:data:`IMAGES_BUILD`).
+    #: :parameter dict config: user configuration.
+    IMAGES_PULL = filters.get("images:pull")
+
+    #: List of images to be pulled when we run ``tutor images push ...``.
+    #: Parameters are the same as for :py:data:`IMAGES_PULL`.
+    IMAGES_PUSH = filters.get("images:push")
+
+    #: List of commands to be executed during initialization. These commands typically
+    #: include database migrations, setting feature flags, etc.
+    #:
+    #: :parameter list[tuple[str, tuple[str, ...]]] tasks: list of ``(service, path)`` tasks.
+    #:
+    #:     - ``service`` is the name of the container in which the task will be executed.
+    #:     - ``path`` is a tuple that corresponds to a template relative path.
+    #:       Example: ``("myplugin", "hooks", "myservice", "pre-init")`` (see:py:data:`IMAGES_BUILD`).
+    #:       The command to execute will be read from that template, after it is rendered.
+    COMMANDS_INIT = filters.get("commands:init")
+
+    #: List of commands to be executed prior to initialization. These commands are run even
+    #: before the mysql databases are created and the migrations are applied.
+    #:
+    #: :parameter list[tuple[str, tuple[str, ...]]] tasks: list of ``(service, path)`` tasks. (see :py:data:`COMMANDS_INIT`).
+    COMMANDS_PRE_INIT = filters.get("commands:pre-init")
+
+    #: List of command line interface (CLI) commands.
+    #:
+    #: :parameter list commands: commands are instances of ``click.Command``. They will
+    #:   all be added as subcommands of the main ``tutor`` command.
+    CLI_COMMANDS = filters.get("cli:commands")
+
+    #: Declare new default configuration settings that don't necessarily have to be saved in the user
+    #: ``config.yml`` file. Default settings may be overridden with ``tutor config save --set=...``, in which
+    #: case they will automatically be added to ``config.yml``.
+    #:
+    #: :parameter list[tuple[str, ...]] items: list of (name, value) new settings. All
+    #:    new entries must be prefixed with the plugin name in all-caps.
+    CONFIG_DEFAULTS = filters.get("config:defaults")
+
+    #: Modify existing settings, either from Tutor core or from other plugins. Beware not to override any
+    #: important setting, such as passwords! Overridden setting values will be printed to stdout when the plugin
+    #: is disabled, such that users have a chance to back them up.
+    #:
+    #: :parameter list[tuple[str, ...]] items: list of (name, value) settings.
+    CONFIG_OVERRIDES = filters.get("config:overrides")
+
+    #: Declare uniqaue configuration settings that must be saved in the user ``config.yml`` file. This is where
+    #: you should declare passwords and randomly-generated values that are different from one environment to the next.
+    #:
+    #: :parameter list[tuple[str, ...]] items: list of (name, value) new settings. All
+    #:   names must be prefixed with the plugin name in all-caps.
+    CONFIG_UNIQUE = filters.get("config:unique")
+
+    #: List of patches that should be inserted in a given location of the templates. The
+    #: filter name must be formatted with the patch name.
+    #: This filter is not so convenient and plugin developers will probably
+    #: prefer :py:data:`ENV_PATCHES`.
+    #:
+    #: :parameter list[str] patches: each item is the unrendered patch content.
+    ENV_PATCH = filters.get_template("env:patches:{0}")
+
+    #: List of patches that should be inserted in a given location of the templates. This is very similar to :py:data:`ENV_PATCH`, except that the patch is added as a ``(name, content)`` tuple.
+    #:
+    #: :parameter list[tuple[str, str]] patches: pairs of (name, content) tuples. Use this
+    #:   filter to modify the Tutor templates.
+    ENV_PATCHES = filters.get("env:patches")
+
+    #: List of all template root folders.
+    #:
+    #: :parameter list[str] templates_root: absolute paths to folders which contain templates.
+    #:   The templates in these folders will then be accessible by the environment
+    #:   renderer using paths that are relative to their template root.
+    ENV_TEMPLATE_ROOTS = filters.get("env:templates:roots")
+
+    #: List of template source/destination targets.
+    #:
+    #: :parameter list[tuple[str, str]] targets: list of (source, destination) pairs.
+    #:   Each source is a path relative to one of the template roots, and each destination
+    #:   is a path relative to the environment root. For instance: adding ``("c/d",
+    #:   "a/b")`` to the filter will cause all files from "c/d" to be rendered to the ``a/b/c/d``
+    #:   subfolder.
+    ENV_TEMPLATE_TARGETS = filters.get("env:templates:targets")
+
+    #: List of `Jinja2 filters <https://jinja.palletsprojects.com/en/latest/templates/#filters>`__ that will be
+    #: available in templates. Jinja2 filters are basically functions that can be used
+    #: as follows within templates::
+    #:
+    #:    {{ "somevalue"|my_filter }}
+    #:
+    #: Note that Jinja2 filters are a completely different thing than the Tutor hook
+    #: filters, although they share the same name.
+    #:
+    #: :parameter filters: list of (name, function) tuples. The function signature
+    #:   should correspond to its usage in templates.
+    ENV_TEMPLATE_FILTERS = filters.get("env:templates:filters")
+
+    #: List of extra variables to be included in all templates.
+    #:
+    #: :parameter filters: list of (name, value) tuples.
+    ENV_TEMPLATE_VARIABLES = filters.get("env:templates:variables")
+
+    #: List of installed plugins. In order to be added to this list, a plugin must first
+    #: be discovered (see :py:data:`Actions.CORE_READY`).
+    #:
+    #: :param list[str] plugins: plugin developers probably don't have to implement this
+    #:   filter themselves, but they can apply it to check for the presence of other
+    #:   plugins.
+    PLUGINS_INSTALLED = filters.get("plugins:installed")
+
+    #: Information about each installed plugin, including its version.
+    #: Keep this information to a single line for easier parsing by 3rd-party scripts.
+    #:
+    #: :param list[tuple[str, str]] versions: each pair is a ``(plugin, info)`` tuple.
+    PLUGINS_INFO = filters.get("plugins:installed:versions")
+
+    #: List of loaded plugins.
+    #:
+    #: :param list[str] plugins: plugin developers probably don't have to modify this
+    #:   filter themselves, but they can apply it to check whether other plugins are enabled.
+    PLUGINS_LOADED = filters.get("plugins:loaded")
+
+
+class Contexts:
+    """
+    Contexts are used to track in which parts of the code filters and actions have been
+    declared. Let's look at an example::
+
+        from tutor import hooks
+
+        with hooks.contexts.enter("c1"):
+            @filters.add("f1") def add_stuff_to_filter(...):
+                ...
+
+    The fact that our custom filter was added in a certain context allows us to later
+    remove it. To do so, we write::
+
+        from tutor import hooks
+        filters.clear("f1", context="c1")
+
+    This makes it easy to disable side-effects by plugins, provided they were created with appropriate contexts.
+
+    Here we list all the contexts that are used across Tutor. It is not expected that
+    plugin developers will ever need to use contexts. But if you do, this is how it
+    should be done::
+
+        from tutor import hooks
+
+        with hooks.Contexts.MY_CONTEXT.enter():
+            # do stuff and all created hooks will include MY_CONTEXT
+
+        # Apply only the hook callbacks that were created within MY_CONTEXT
+        hooks.Actions.MY_ACTION.do(context=str(hooks.Contexts.MY_CONTEXT))
+        hooks.Filters.MY_FILTER.apply(context=hooks.Contexts.MY_CONTEXT.name)
+    """
+
+    #: We enter this context whenever we create hooks for a specific application or :
+    #: plugin. For instance, plugin "myplugin" will be enabled within the "app:myplugin"
+    #: context.
+    APP = contexts.ContextTemplate("app:{0}")
+
+    #: Plugins will be installed and enabled within this context.
+    PLUGINS = contexts.Context("plugins")
+
+    #: YAML-formatted v0 plugins will be installed within that context.
+    PLUGINS_V0_YAML = contexts.Context("plugins:v0:yaml")
+
+    #: Python entrypoint plugins will be installed within that context.
+    PLUGINS_V0_ENTRYPOINT = contexts.Context("plugins:v0:entrypoint")

tutor/hooks/contexts.py

@@ -0,0 +1,84 @@
+# The Tutor plugin system is licensed under the terms of the Apache 2.0 license.
+__license__ = "Apache 2.0"
+
+import typing as t
+from contextlib import contextmanager
+
+
+class Context:
+    CURRENT: t.List[str] = []
+
+    def __init__(self, name: str):
+        self.name = name
+
+    @contextmanager
+    def enter(self) -> t.Iterator[None]:
+        try:
+            Context.CURRENT.append(self.name)
+            yield
+        finally:
+            Context.CURRENT.pop()
+
+
+class ContextTemplate:
+    """
+    Context templates are for filters for which the name needs to be formatted
+    before the filter can be applied.
+    """
+
+    def __init__(self, name: str):
+        self.template = name
+
+    def __repr__(self) -> str:
+        return f"{self.__class__.__name__}('{self.template}')"
+
+    def __call__(self, *args: t.Any, **kwargs: t.Any) -> Context:
+        return Context(self.template.format(*args, **kwargs))
+
+
+class Contextualized:
+    """
+    This is a simple class to store the current context in hooks.
+
+    The current context is stored as a static variable.
+    """
+
+    def __init__(self) -> None:
+        self.contexts = Context.CURRENT[:]
+
+    def is_in_context(self, context: t.Optional[str]) -> bool:
+        return context is None or context in self.contexts
+
+
+def enter(name: str) -> t.ContextManager[None]:
+    """
+    Identify created hooks with one or multiple context strings.
+
+    :param name: name of the context that will be attached to hooks.
+    :rtype t.ContextManager[None]:
+
+    Usage::
+
+        from tutor import hooks
+
+        with hooks.contexts.enter("my-context"):
+            # declare new actions and filters
+            ...
+
+        # Later on, actions and filters can be disabled with:
+        hooks.actions.clear_all(context="my-context")
+        hooks.filters.clear_all(context="my-context")
+
+    This is a context manager that will attach a context name to all hook callbacks
+    created within its scope. The purpose of contexts is to solve an issue that
+    is inherent to pluggable hooks: it is difficult to track in which part of the
+    code each hook callback was created. This makes things hard to debug when a single
+    hook callback goes wrong. It also makes it impossible to disable some hook callbacks after
+    they have been created.
+
+    We resolve this issue by storing the current contexts in a static list.
+    Whenever a hook is created, the list of current contexts is copied as a
+    ``contexts`` attribute. This attribute can be later examined, either for
+    removal or for limiting the set of hook callbacks that should be applied.
+    """
+    return Context(name).enter()

tutor/hooks/filters.py

@@ -0,0 +1,272 @@
+# The Tutor plugin system is licensed under the terms of the Apache 2.0 license.
+__license__ = "Apache 2.0"
+
+import sys
+import typing as t
+
+from . import contexts
+
+# For now, this signature is not very restrictive. In the future, we could improve it by writing:
+#
+# P = ParamSpec("P")
+# CallableFilter = t.Callable[Concatenate[T, P], T]
+#
+# See PEP-612: https://www.python.org/dev/peps/pep-0612/
+# Unfortunately, this piece of code fails because of a bug in mypy:
+# https://github.com/python/mypy/issues/11833
+# https://github.com/python/mypy/issues/8645
+# https://github.com/python/mypy/issues/5876
+# https://github.com/python/typing/issues/696
+T = t.TypeVar("T")
+CallableFilter = t.Callable[..., t.Any]
+
+
+class FilterCallback(contexts.Contextualized):
+    def __init__(self, func: CallableFilter):
+        super().__init__()
+        self.func = func
+
+    def apply(
+        self, value: T, *args: t.Any, context: t.Optional[str] = None, **kwargs: t.Any
+    ) -> T:
+        if self.is_in_context(context):
+            value = self.func(value, *args, **kwargs)
+        return value
+
+
+class Filter:
+    """
+    Each filter is associated to a name and a list of callbacks.
+    """
+
+    INDEX: t.Dict[str, "Filter"] = {}
+
+    def __init__(self, name: str) -> None:
+        self.name = name
+        self.callbacks: t.List[FilterCallback] = []
+
+    def __repr__(self) -> str:
+        return f"{self.__class__.__name__}('{self.name}')"
+
+    @classmethod
+    def get(cls, name: str) -> "Filter":
+        """
+        Get an existing action with the given name from the index, or create one.
+        """
+        return cls.INDEX.setdefault(name, cls(name))
+
+    def add(self) -> t.Callable[[CallableFilter], CallableFilter]:
+        def inner(func: CallableFilter) -> CallableFilter:
+            self.callbacks.append(FilterCallback(func))
+            return func
+
+        return inner
+
+    def add_item(self, item: T) -> None:
+        self.add_items([item])
+
+    def add_items(self, items: t.List[T]) -> None:
+        @self.add()
+        def callback(value: t.List[T], *_args: t.Any, **_kwargs: t.Any) -> t.List[T]:
+            return value + items
+
+    def iterate(
+        self, *args: t.Any, context: t.Optional[str] = None, **kwargs: t.Any
+    ) -> t.Iterator[T]:
+        yield from self.apply([], *args, context=context, **kwargs)
+
+    def apply(
+        self,
+        value: T,
+        *args: t.Any,
+        context: t.Optional[str] = None,
+        **kwargs: t.Any,
+    ) -> T:
+        """
+        Apply all declared filters to a single value, passing along the additional arguments.
+
+        The return value of every filter is passed as the first argument to the next callback.
+
+        Usage::
+
+            results = filters.apply("my-filter", ["item0"])
+
+        :type value: object
+        :rtype: same as the type of ``value``.
+        """
+        for callback in self.callbacks:
+            try:
+                value = callback.apply(value, *args, context=context, **kwargs)
+            except:
+                sys.stderr.write(
+                    f"Error applying filter '{self.name}': func={callback.func} contexts={callback.contexts}'\n"
+                )
+                raise
+        return value
+
+    def clear(self, context: t.Optional[str] = None) -> None:
+        """
+        Clear any previously defined filter with the given name and context.
+        """
+        self.callbacks = [
+            callback
+            for callback in self.callbacks
+            if not callback.is_in_context(context)
+        ]
+
+
+class FilterTemplate:
+    """
+    Filter templates are for filters for which the name needs to be formatted
+    before the filter can be applied.
+    """
+
+    def __init__(self, name: str):
+        self.template = name
+
+    def __repr__(self) -> str:
+        return f"{self.__class__.__name__}('{self.template}')"
+
+    def __call__(self, *args: t.Any, **kwargs: t.Any) -> Filter:
+        return get(self.template.format(*args, **kwargs))
+
+
+# Syntactic sugar
+get = Filter.get
+
+
+def get_template(name: str) -> FilterTemplate:
+    """
+    Create a filter with a template name.
+
+    Templated filters must be formatted with ``(*args)`` before being applied. For example::
+
+        filter_template = filters.get_template("namespace:{0}")
+        named_filter = filter_template("name")
+
+        @named_filter.add()
+        def my_callback():
+            ...
+
+        named_filter.do()
+    """
+    return FilterTemplate(name)
+
+
+def add(name: str) -> t.Callable[[CallableFilter], CallableFilter]:
+    """
+    Decorator for functions that will be applied to a single named filter.
+
+    :param name: name of the filter to which the decorated function should be added.
+
+    The return value of each filter function callback will be passed as the first argument to the next one.
+
+    Usage::
+
+        from tutor import hooks
+
+        @hooks.filters.add("my-filter")
+        def my_func(value, some_other_arg):
+            # Do something with `value`
+            ...
+            return value
+
+        # After filters have been created, the result of calling all filter callbacks is obtained by running:
+        hooks.filters.apply("my-filter", initial_value, some_other_argument_value)
+    """
+    return Filter.get(name).add()
+
+
+def add_item(name: str, item: T) -> None:
+    """
+    Convenience function to add a single item to a filter that returns a list of items.
+
+    :param name: filter name.
+    :param object item: item that will be appended to the resulting list.
+
+    Usage::
+
+        from tutor import hooks
+
+        hooks.filters.add_item("my-filter", "item1")
+        hooks.filters.add_item("my-filter", "item2")
+
+        assert ["item1", "item2"] == hooks.filters.apply("my-filter", [])
+    """
+    get(name).add_item(item)
+
+
+def add_items(name: str, items: t.List[T]) -> None:
+    """
+    Convenience function to add multiple item to a filter that returns a list of items.
+
+    :param name: filter name.
+    :param list[object] items: items that will be appended to the resulting list.
+
+    Usage::
+
+        from tutor import hooks
+
+        hooks.filters.add_items("my-filter", ["item1", "item2"])
+
+        assert ["item1", "item2"] == hooks.filters.apply("my-filter", [])
+    """
+    get(name).add_items(items)
+
+
+def iterate(
+    name: str, *args: t.Any, context: t.Optional[str] = None, **kwargs: t.Any
+) -> t.Iterator[T]:
+    """
+    Convenient function to iterate over the results of a filter result list.
+
+    This pieces of code are equivalent::
+
+        for value in filters.apply("my-filter", [], *args, **kwargs):
+            ...
+
+        for value in filters.iterate("my-filter", *args, **kwargs):
+            ...
+
+    :rtype iterator[T]: iterator over the list items from the filter with the same name.
+    """
+    yield from Filter.get(name).iterate(*args, context=context, **kwargs)
+
+
+def apply(
+    name: str,
+    value: T,
+    *args: t.Any,
+    context: t.Optional[str] = None,
+    **kwargs: t.Any,
+) -> T:
+    """
+    Apply all declared filters to a single value, passing along the additional arguments.
+
+    The return value of every filter is passed as the first argument to the next callback.
+
+    Usage::
+
+        results = filters.apply("my-filter", ["item0"])
+
+    :type value: object
+    :rtype: same as the type of ``value``.
+    """
+    return Filter.get(name).apply(value, *args, context=context, **kwargs)
+
+
+def clear_all(context: t.Optional[str] = None) -> None:
+    """
+    Clear any previously defined filter with the  given context.
+    """
+    for name in Filter.INDEX:
+        clear(name, context=context)
+
+
+def clear(name: str, context: t.Optional[str] = None) -> None:
+    """
+    Clear any previously defined filter with the given name and context.
+    """
+    filtre = Filter.INDEX.get(name)
+    if filtre:
+        filtre.clear(context=context)

tutor/images.py

@@ -8,15 +8,15 @@ def get_tag(config: Config, name: str) -> str:
 
 
 def build(path: str, tag: str, *args: str) -> None:
-    fmt.echo_info("Building image {}".format(tag))
+    fmt.echo_info(f"Building image {tag}")
     utils.docker("build", "-t", tag, *args, path)
 
 
 def pull(tag: str) -> None:
-    fmt.echo_info("Pulling image {}".format(tag))
+    fmt.echo_info(f"Pulling image {tag}")
     utils.docker("pull", tag)
 
 
 def push(tag: str) -> None:
-    fmt.echo_info("Pushing image {}".format(tag))
+    fmt.echo_info(f"Pushing image {tag}")
     utils.docker("push", tag)

tutor/interactive.py

@@ -18,7 +18,7 @@ def load_user_config(root: str, interactive: bool = True) -> Config:
 
 
 def ask_questions(config: Config) -> None:
-    defaults = tutor_config.get_defaults(config)
+    defaults = tutor_config.get_defaults()
     run_for_prod = config.get("LMS_HOST") != "local.overhang.io"
     run_for_prod = click.confirm(
         fmt.question(
@@ -38,9 +38,8 @@ def ask_questions(config: Config) -> None:
         )
         for k, v in dev_values.items():
             config[k] = v
-            fmt.echo_info("    {} = {}".format(k, v))
-
-    if run_for_prod:
+            fmt.echo_info(f"    {k} = {v}")
+    else:
         ask("Your website domain name for students (LMS)", "LMS_HOST", config, defaults)
         lms_host = get_typed(config, "LMS_HOST", str)
         if "localhost" in lms_host:

tutor/jobs.py

@@ -1,7 +1,7 @@
-from typing import Dict, Iterator, List, Optional, Tuple, Union
+import typing as t
 
-from . import env, fmt, plugins
-from .types import Config, get_typed
+from tutor import env, fmt, hooks
+from tutor.types import Config, get_typed
 
 BASE_OPENEDX_COMMAND = """
 export DJANGO_SETTINGS_MODULE=$SERVICE_VARIANT.envs.$SETTINGS
@@ -36,44 +36,48 @@ class BaseJobRunner:
         """
         raise NotImplementedError
 
-    def iter_plugin_hooks(
-        self, hook: str
-    ) -> Iterator[Tuple[str, Union[Dict[str, str], List[str]]]]:
-        yield from plugins.iter_hooks(self.config, hook)
-
 
 class BaseComposeJobRunner(BaseJobRunner):
     def docker_compose(self, *command: str) -> int:
         raise NotImplementedError
 
 
-def initialise(runner: BaseJobRunner, limit_to: Optional[str] = None) -> None:
+@hooks.Actions.CORE_READY.add()
+def _add_core_init_tasks() -> None:
+    """
+    Declare core init scripts at runtime.
+
+    The context is important, because it allows us to select the init scripts based on
+    the --limit argument.
+    """
+    with hooks.Contexts.APP("mysql").enter():
+        hooks.Filters.COMMANDS_INIT.add_item(("mysql", ("hooks", "mysql", "init")))
+    with hooks.Contexts.APP("lms").enter():
+        hooks.Filters.COMMANDS_INIT.add_item(("lms", ("hooks", "lms", "init")))
+    with hooks.Contexts.APP("cms").enter():
+        hooks.Filters.COMMANDS_INIT.add_item(("cms", ("hooks", "cms", "init")))
+
+
+def initialise(runner: BaseJobRunner, limit_to: t.Optional[str] = None) -> None:
     fmt.echo_info("Initialising all services...")
-    if limit_to is None or limit_to == "mysql":
-        fmt.echo_info("Initialising mysql...")
-        runner.run_job_from_template("mysql", "hooks", "mysql", "init")
-    for plugin_name, hook in runner.iter_plugin_hooks("pre-init"):
-        if limit_to is None or limit_to == plugin_name:
-            for service in hook:
-                fmt.echo_info(
-                    f"Plugin {plugin_name}: running pre-init for service {service}..."
-                )
-                runner.run_job_from_template(
-                    service, plugin_name, "hooks", service, "pre-init"
-                )
-    for service in ["lms", "cms"]:
-        if limit_to is None or limit_to == service:
-            fmt.echo_info(f"Initialising {service}...")
-            runner.run_job_from_template(service, "hooks", service, "init")
-    for plugin_name, hook in runner.iter_plugin_hooks("init"):
-        if limit_to is None or limit_to == plugin_name:
-            for service in hook:
-                fmt.echo_info(
-                    f"Plugin {plugin_name}: running init for service {service}..."
-                )
-                runner.run_job_from_template(
-                    service, plugin_name, "hooks", service, "init"
-                )
+    filter_context = hooks.Contexts.APP(limit_to).name if limit_to else None
+
+    # Pre-init tasks
+    iter_pre_init_tasks: t.Iterator[
+        t.Tuple[str, t.Iterable[str]]
+    ] = hooks.Filters.COMMANDS_PRE_INIT.iterate(context=filter_context)
+    for service, path in iter_pre_init_tasks:
+        fmt.echo_info(f"Running pre-init task: {'/'.join(path)}")
+        runner.run_job_from_template(service, *path)
+
+    # Init tasks
+    iter_init_tasks: t.Iterator[
+        t.Tuple[str, t.Iterable[str]]
+    ] = hooks.Filters.COMMANDS_INIT.iterate(context=filter_context)
+    for service, path in iter_init_tasks:
+        fmt.echo_info(f"Running init task: {'/'.join(path)}")
+        runner.run_job_from_template(service, *path)
+
     fmt.echo_info("All services initialised.")
 
 
@@ -82,7 +86,7 @@ def create_user_command(
     staff: bool,
     username: str,
     email: str,
-    password: Optional[str] = None,
+    password: t.Optional[str] = None,
 ) -> str:
     command = BASE_OPENEDX_COMMAND
 
@@ -113,7 +117,9 @@ def import_demo_course(runner: BaseJobRunner) -> None:
     runner.run_job_from_template("cms", "hooks", "cms", "importdemocourse")
 
 
-def set_theme(theme_name: str, domain_names: List[str], runner: BaseJobRunner) -> None:
+def set_theme(
+    theme_name: str, domain_names: t.List[str], runner: BaseJobRunner
+) -> None:
     """
     For each domain, get or create a Site object and assign the selected theme.
     """
@@ -136,7 +142,7 @@ site.themes.create(theme_dir_name='{theme_name}')
     runner.run_job("lms", command)
 
 
-def get_all_openedx_domains(config: Config) -> List[str]:
+def get_all_openedx_domains(config: Config) -> t.List[str]:
     return [
         get_typed(config, "LMS_HOST", str),
         get_typed(config, "LMS_HOST", str) + ":8000",

tutor/plugins.py

@@ -1,439 +0,0 @@
-import importlib
-import os
-from copy import deepcopy
-from glob import glob
-from typing import Any, Dict, Iterator, List, Optional, Tuple, Type, Union
-
-import appdirs
-import click
-import pkg_resources
-
-from . import exceptions, fmt, serialize
-from .__about__ import __app__
-from .types import Config, get_typed
-
-CONFIG_KEY = "PLUGINS"
-
-
-class BasePlugin:
-    """
-    Tutor plugins are defined by a name and an object that implements one or more of the
-    following properties:
-
-    `config` (dict str->dict(str->str)): contains "add", "defaults", "set" keys. Entries
-    in these dicts will be added or override the global configuration. Keys in "add" and
-    "defaults" will be prefixed by the plugin name in uppercase.
-
-    `patches` (dict str->str): entries in this dict will be used to patch the rendered
-    Tutor templates. For instance, to add "somecontent" to a template that includes '{{
-    patch("mypatch") }}', set: `patches["mypatch"] = "somecontent"`. It is recommended
-    to store all patches in separate files, and to dynamically list patches by listing
-    the contents of a "patches"  subdirectory.
-
-    `templates` (str): path to a directory that includes new template files for the
-    plugin. It is recommended that all files in the template directory are stored in a
-    `myplugin` folder to avoid conflicts with other plugins. Plugin templates are useful
-    for content re-use, e.g: "{% include 'myplugin/mytemplate.html'}".
-
-    `hooks` (dict str->list[str]): hooks are commands that will be run at various points
-    during the lifetime of the platform. For instance, to run `service1` and `service2`
-    in sequence during initialisation, you should define:
-
-        hooks["init"] = ["service1", "service2"]
-
-    It is then assumed that there are `myplugin/hooks/service1/init` and
-    `myplugin/hooks/service2/init` templates in the plugin `templates` directory.
-
-    `command` (click.Command): if a plugin exposes a `command` attribute, users will be able to run it from the command line as `tutor pluginname`.
-    """
-
-    INSTALLED: List["BasePlugin"] = []
-    _IS_LOADED = False
-
-    def __init__(self, name: str, obj: Any) -> None:
-        self.name = name
-        self.config = self.load_config(obj, self.name)
-        self.patches = self.load_patches(obj, self.name)
-        self.hooks = self.load_hooks(obj, self.name)
-
-        templates_root = get_callable_attr(obj, "templates", default=None)
-        if templates_root is not None:
-            assert isinstance(templates_root, str)
-        self.templates_root = templates_root
-
-        command = getattr(obj, "command", None)
-        if command is not None:
-            assert isinstance(command, click.Command)
-        self.command: Optional[click.Command] = command
-
-    @staticmethod
-    def load_config(obj: Any, plugin_name: str) -> Dict[str, Config]:
-        """
-        Load config and check types.
-        """
-        config = get_callable_attr(obj, "config", {})
-        if not isinstance(config, dict):
-            raise exceptions.TutorError(
-                f"Invalid config in plugin {plugin_name}. Expected dict, got {config.__class__}."
-            )
-        for name, subconfig in config.items():
-            if not isinstance(name, str):
-                raise exceptions.TutorError(
-                    f"Invalid config entry '{name}' in plugin {plugin_name}. Expected str, got {config.__class__}."
-                )
-            if not isinstance(subconfig, dict):
-                raise exceptions.TutorError(
-                    f"Invalid config entry '{name}' in plugin {plugin_name}. Expected str keys, got {config.__class__}."
-                )
-            for key in subconfig.keys():
-                if not isinstance(key, str):
-                    raise exceptions.TutorError(
-                        f"Invalid config entry '{name}.{key}' in plugin {plugin_name}. Expected str, got {key.__class__}."
-                    )
-        return config
-
-    @staticmethod
-    def load_patches(obj: Any, plugin_name: str) -> Dict[str, str]:
-        """
-        Load patches and check the types are right.
-        """
-        patches = get_callable_attr(obj, "patches", {})
-        if not isinstance(patches, dict):
-            raise exceptions.TutorError(
-                f"Invalid patches in plugin {plugin_name}. Expected dict, got {patches.__class__}."
-            )
-        for patch_name, content in patches.items():
-            if not isinstance(patch_name, str):
-                raise exceptions.TutorError(
-                    f"Invalid patch name '{patch_name}' in plugin {plugin_name}. Expected str, got {patch_name.__class__}."
-                )
-            if not isinstance(content, str):
-                raise exceptions.TutorError(
-                    f"Invalid patch '{patch_name}' in plugin {plugin_name}. Expected str, got {content.__class__}."
-                )
-        return patches
-
-    @staticmethod
-    def load_hooks(
-        obj: Any, plugin_name: str
-    ) -> Dict[str, Union[Dict[str, str], List[str]]]:
-        """
-        Load hooks and check types.
-        """
-        hooks = get_callable_attr(obj, "hooks", default={})
-        if not isinstance(hooks, dict):
-            raise exceptions.TutorError(
-                f"Invalid hooks in plugin {plugin_name}. Expected dict, got {hooks.__class__}."
-            )
-        for hook_name, hook in hooks.items():
-            if not isinstance(hook_name, str):
-                raise exceptions.TutorError(
-                    f"Invalid hook name '{hook_name}' in plugin {plugin_name}. Expected str, got {hook_name.__class__}."
-                )
-            if isinstance(hook, list):
-                for service in hook:
-                    if not isinstance(service, str):
-                        raise exceptions.TutorError(
-                            f"Invalid service in hook '{hook_name}' from plugin {plugin_name}. Expected str, got {service.__class__}."
-                        )
-            elif isinstance(hook, dict):
-                for name, value in hook.items():
-                    if not isinstance(name, str) or not isinstance(value, str):
-                        raise exceptions.TutorError(
-                            f"Invalid hook '{hook_name}' in plugin {plugin_name}. Only str -> str entries are supported."
-                        )
-            else:
-                raise exceptions.TutorError(
-                    f"Invalid hook '{hook_name}' in plugin {plugin_name}. Expected dict or list, got {hook.__class__}."
-                )
-        return hooks
-
-    def config_key(self, key: str) -> str:
-        """
-        Config keys in the "add" and "defaults" dicts should be prefixed by the plugin name, in uppercase.
-        """
-        return self.name.upper() + "_" + key
-
-    @property
-    def config_add(self) -> Config:
-        return self.config.get("add", {})
-
-    @property
-    def config_set(self) -> Config:
-        return self.config.get("set", {})
-
-    @property
-    def config_defaults(self) -> Config:
-        return self.config.get("defaults", {})
-
-    @property
-    def version(self) -> str:
-        raise NotImplementedError
-
-    @classmethod
-    def iter_installed(cls) -> Iterator["BasePlugin"]:
-        if not cls._IS_LOADED:
-            for plugin in cls.iter_load():
-                cls.INSTALLED.append(plugin)
-            cls._IS_LOADED = True
-        yield from cls.INSTALLED
-
-    @classmethod
-    def iter_load(cls) -> Iterator["BasePlugin"]:
-        raise NotImplementedError
-
-    @classmethod
-    def clear_cache(cls) -> None:
-        cls._IS_LOADED = False
-        cls.INSTALLED.clear()
-
-
-class EntrypointPlugin(BasePlugin):
-    """
-    Entrypoint plugins are regular python packages that have a 'tutor.plugin.v0' entrypoint.
-
-    The API for Tutor plugins is currently in development. The entrypoint will switch to
-    'tutor.plugin.v1' once it is stabilised.
-    """
-
-    ENTRYPOINT = "tutor.plugin.v0"
-
-    def __init__(self, entrypoint: pkg_resources.EntryPoint) -> None:
-        super().__init__(entrypoint.name, entrypoint.load())
-        self.entrypoint = entrypoint
-
-    @property
-    def version(self) -> str:
-        if not self.entrypoint.dist:
-            return "0.0.0"
-        return self.entrypoint.dist.version
-
-    @classmethod
-    def iter_load(cls) -> Iterator["EntrypointPlugin"]:
-        for entrypoint in pkg_resources.iter_entry_points(cls.ENTRYPOINT):
-            try:
-                error: Optional[str] = None
-                yield cls(entrypoint)
-            except pkg_resources.VersionConflict as e:
-                error = e.report()
-            except Exception as e:  # pylint: disable=broad-except
-                error = str(e)
-            if error:
-                fmt.echo_error(
-                    f"Failed to load entrypoint '{entrypoint.name} = {entrypoint.module_name}' from distribution {entrypoint.dist}: {error}"
-                )
-
-
-class OfficialPlugin(BasePlugin):
-    """
-    Official plugins have a "plugin" module which exposes a __version__ attribute.
-    Official plugins should be manually added by calling `OfficialPlugin.load()`.
-    """
-
-    @classmethod
-    def load(cls, name: str) -> BasePlugin:
-        plugin = cls(name)
-        cls.INSTALLED.append(plugin)
-        return plugin
-
-    def __init__(self, name: str):
-        self.module = importlib.import_module(f"tutor{name}.plugin")
-        super().__init__(name, self.module)
-
-    @property
-    def version(self) -> str:
-        version = getattr(self.module, "__version__")
-        if not isinstance(version, str):
-            raise TypeError("OfficialPlugin __version__ must be 'str'")
-        return version
-
-    @classmethod
-    def iter_load(cls) -> Iterator[BasePlugin]:
-        yield from []
-
-
-class DictPlugin(BasePlugin):
-    ROOT_ENV_VAR_NAME = "TUTOR_PLUGINS_ROOT"
-    ROOT = os.path.expanduser(
-        os.environ.get(ROOT_ENV_VAR_NAME, "")
-    ) or appdirs.user_data_dir(appname=__app__ + "-plugins")
-
-    def __init__(self, data: Config):
-        name = data["name"]
-        if not isinstance(name, str):
-            raise exceptions.TutorError(
-                f"Invalid plugin name: '{name}'. Expected str, got {name.__class__}"
-            )
-
-        # Create a generic object (sort of a named tuple) which will contain all key/values from data
-        class Module:
-            pass
-
-        obj = Module()
-        for key, value in data.items():
-            setattr(obj, key, value)
-
-        super().__init__(name, obj)
-
-        version = data["version"]
-        if not isinstance(version, str):
-            raise TypeError("DictPlugin.__version__ must be str")
-        self._version: str = version
-
-    @property
-    def version(self) -> str:
-        return self._version
-
-    @classmethod
-    def iter_load(cls) -> Iterator[BasePlugin]:
-        for path in glob(os.path.join(cls.ROOT, "*.yml")):
-            with open(path, encoding="utf-8") as f:
-                data = serialize.load(f)
-                if not isinstance(data, dict):
-                    raise exceptions.TutorError(
-                        f"Invalid plugin: {path}. Expected dict."
-                    )
-                try:
-                    yield cls(data)
-                except KeyError as e:
-                    raise exceptions.TutorError(
-                        f"Invalid plugin: {path}. Missing key: {e.args[0]}"
-                    )
-
-
-class Plugins:
-    PLUGIN_CLASSES: List[Type[BasePlugin]] = [
-        OfficialPlugin,
-        EntrypointPlugin,
-        DictPlugin,
-    ]
-
-    def __init__(self, config: Config):
-        self.config = deepcopy(config)
-        # patches has the following structure:
-        # {patch_name -> {plugin_name -> "content"}}
-        self.patches: Dict[str, Dict[str, str]] = {}
-        # some hooks have a dict-like structure, like "build", others are list of services.
-        self.hooks: Dict[str, Dict[str, Union[Dict[str, str], List[str]]]] = {}
-        self.template_roots: Dict[str, str] = {}
-
-        for plugin in self.iter_enabled():
-            for patch_name, content in plugin.patches.items():
-                if patch_name not in self.patches:
-                    self.patches[patch_name] = {}
-                self.patches[patch_name][plugin.name] = content
-
-            for hook_name, services in plugin.hooks.items():
-                if hook_name not in self.hooks:
-                    self.hooks[hook_name] = {}
-                self.hooks[hook_name][plugin.name] = services
-
-    @classmethod
-    def clear_cache(cls) -> None:
-        for PluginClass in cls.PLUGIN_CLASSES:
-            PluginClass.clear_cache()
-
-    @classmethod
-    def iter_installed(cls) -> Iterator[BasePlugin]:
-        """
-        Iterate on all installed plugins. Plugins are deduplicated by name. The list of installed plugins is cached to
-        prevent too many re-computations, which happens a lot.
-        """
-        installed_plugin_names = set()
-        plugins = []
-        for PluginClass in cls.PLUGIN_CLASSES:
-            for plugin in PluginClass.iter_installed():
-                if plugin.name not in installed_plugin_names:
-                    installed_plugin_names.add(plugin.name)
-                    plugins.append(plugin)
-        plugins = sorted(plugins, key=lambda plugin: plugin.name)
-        yield from plugins
-
-    def iter_enabled(self) -> Iterator[BasePlugin]:
-        for plugin in self.iter_installed():
-            if is_enabled(self.config, plugin.name):
-                yield plugin
-
-    def iter_patches(self, name: str) -> Iterator[Tuple[str, str]]:
-        plugin_patches = self.patches.get(name, {})
-        plugins = sorted(plugin_patches.keys())
-        for plugin in plugins:
-            yield plugin, plugin_patches[plugin]
-
-    def iter_hooks(
-        self, hook_name: str
-    ) -> Iterator[Tuple[str, Union[Dict[str, str], List[str]]]]:
-        yield from self.hooks.get(hook_name, {}).items()
-
-
-def get_callable_attr(
-    plugin: Any, attr_name: str, default: Optional[Any] = None
-) -> Optional[Any]:
-    attr = getattr(plugin, attr_name, default)
-    if callable(attr):
-        attr = attr()
-    return attr
-
-
-def is_installed(name: str) -> bool:
-    for plugin in iter_installed():
-        if name == plugin.name:
-            return True
-    return False
-
-
-def iter_installed() -> Iterator[BasePlugin]:
-    yield from Plugins.iter_installed()
-
-
-def enable(config: Config, name: str) -> None:
-    if not is_installed(name):
-        raise exceptions.TutorError(f"plugin '{name}' is not installed.")
-    if is_enabled(config, name):
-        return
-    enabled = enabled_plugins(config)
-    enabled.append(name)
-    enabled.sort()
-
-
-def disable(config: Config, plugin: BasePlugin) -> None:
-    # Remove plugin-specific set config
-    for key in plugin.config_set.keys():
-        config.pop(key, None)
-
-    # Remove plugin from list of enabled plugins
-    enabled = enabled_plugins(config)
-    while plugin.name in enabled:
-        enabled.remove(plugin.name)
-
-
-def get_enabled(config: Config, name: str) -> BasePlugin:
-    for plugin in iter_enabled(config):
-        if plugin.name == name:
-            return plugin
-    raise ValueError(f"Enabled plugin {name} could not be found.")
-
-
-def iter_enabled(config: Config) -> Iterator[BasePlugin]:
-    yield from Plugins(config).iter_enabled()
-
-
-def is_enabled(config: Config, name: str) -> bool:
-    return name in enabled_plugins(config)
-
-
-def enabled_plugins(config: Config) -> List[str]:
-    if not config.get(CONFIG_KEY):
-        config[CONFIG_KEY] = []
-    plugins = get_typed(config, CONFIG_KEY, list)
-    return plugins
-
-
-def iter_patches(config: Config, name: str) -> Iterator[Tuple[str, str]]:
-    yield from Plugins(config).iter_patches(name)
-
-
-def iter_hooks(
-    config: Config, hook_name: str
-) -> Iterator[Tuple[str, Union[Dict[str, str], List[str]]]]:
-    yield from Plugins(config).iter_hooks(hook_name)

tutor/plugins/__init__.py

@@ -0,0 +1,122 @@
+"""
+Provide API for plugin features.
+"""
+import typing as t
+from copy import deepcopy
+
+from tutor import exceptions, fmt, hooks
+from tutor.types import Config, get_typed
+
+# Import modules to trigger hook creation
+from . import v0, v1
+
+
+@hooks.Actions.PLUGINS_LOADED.add()
+def _convert_plugin_patches() -> None:
+    """
+    Some patches are added as (name, content) tuples with the ENV_PATCHES
+    filter. We convert these patches to add them to ENV_PATCH. This makes it
+    easier for end-user to declare patches, and it's more performant.
+
+    This action is run after plugins have been loaded.
+    """
+    patches: t.Iterable[t.Tuple[str, str]] = hooks.Filters.ENV_PATCHES.iterate()
+    for name, content in patches:
+        hooks.Filters.ENV_PATCH(name).add_item(content)
+
+
+def is_installed(name: str) -> bool:
+    """
+    Return true if the plugin is installed.
+    """
+    return name in iter_installed()
+
+
+def iter_installed() -> t.Iterator[str]:
+    """
+    Iterate on all installed plugins, sorted by name.
+
+    This will yield all plugins, including those that have the same name.
+
+    The CORE_READY action must have been triggered prior to calling this function,
+    otherwise no installed plugin will be detected.
+    """
+    plugins: t.Iterator[str] = hooks.Filters.PLUGINS_INSTALLED.iterate()
+    yield from sorted(plugins)
+
+
+def iter_info() -> t.Iterator[t.Tuple[str, t.Optional[str]]]:
+    """
+    Iterate on the information of all installed plugins.
+
+    Yields (<plugin name>, <info>) tuples.
+    """
+    versions: t.Iterator[
+        t.Tuple[str, t.Optional[str]]
+    ] = hooks.Filters.PLUGINS_INFO.iterate()
+    yield from sorted(versions, key=lambda v: v[0])
+
+
+def is_loaded(name: str) -> bool:
+    return name in iter_loaded()
+
+
+def load_all(names: t.Iterable[str]) -> None:
+    """
+    Load all plugins one by one.
+
+    Plugins are loaded in alphabetical order. We ignore plugins which failed to load.
+    After all plugins have been loaded, the PLUGINS_LOADED action is triggered.
+    """
+    names = sorted(set(names))
+    for name in names:
+        try:
+            load(name)
+        except exceptions.TutorError as e:
+            fmt.echo_alert(f"Failed to enable plugin '{name}' : {e.args[0]}")
+    hooks.Actions.PLUGINS_LOADED.do()
+
+
+def load(name: str) -> None:
+    """
+    Load a given plugin, thus declaring all its hooks.
+
+    Loading a plugin is done within a context, such that we can remove all hooks when a
+    plugin is disabled, or during unit tests.
+    """
+    if not is_installed(name):
+        raise exceptions.TutorError(f"plugin '{name}' is not installed.")
+    with hooks.Contexts.PLUGINS.enter():
+        with hooks.Contexts.APP(name).enter():
+            hooks.Actions.PLUGIN_LOADED(name).do()
+            hooks.Filters.PLUGINS_LOADED.add_item(name)
+
+
+def iter_loaded() -> t.Iterator[str]:
+    """
+    Iterate on the list of loaded plugin names, sorted in alphabetical order.
+
+    Note that loaded plugin names are deduplicated. Thus, if two plugins have
+    the same name, just one name will be displayed.
+    """
+    plugins: t.Iterable[str] = hooks.Filters.PLUGINS_LOADED.iterate()
+    yield from sorted(set(plugins))
+
+
+def iter_patches(name: str) -> t.Iterator[str]:
+    """
+    Yields: patch (str)
+    """
+    yield from hooks.Filters.ENV_PATCH(name).iterate()
+
+
+def unload(plugin: str) -> None:
+    """
+    Remove all filters and actions associated to a given plugin.
+    """
+    hooks.clear_all(context=hooks.Contexts.APP(plugin).name)
+
+
+@hooks.Actions.PLUGIN_UNLOADED.add(priority=50)
+def _unload_on_disable(plugin: str, _root: str, _config: Config) -> None:
+    unload(plugin)

tutor/plugins/base.py

@@ -0,0 +1,16 @@
+import os
+
+import appdirs
+
+from tutor.__about__ import __app__
+
+PLUGINS_ROOT_ENV_VAR_NAME = "TUTOR_PLUGINS_ROOT"
+
+# Folder path which contains *.yml and *.py file plugins.
+# On linux this is typically ``~/.local/share/tutor-plugins``. On the nightly branch
+# this will be ``~/.local/share/tutor-plugins-nightly``.
+# The path can be overridden by defining the ``TUTOR_PLUGINS_ROOT`` environment
+# variable.
+PLUGINS_ROOT = os.path.expanduser(
+    os.environ.get(PLUGINS_ROOT_ENV_VAR_NAME, "")
+) or appdirs.user_data_dir(appname=__app__ + "-plugins")

tutor/plugins/v0.py

@@ -0,0 +1,395 @@
+import importlib
+import importlib.util
+import os
+import typing as t
+from glob import glob
+
+import click
+import pkg_resources
+
+from tutor import exceptions, fmt, hooks, serialize
+from tutor.__about__ import __app__
+from tutor.types import Config
+
+from .base import PLUGINS_ROOT
+
+
+class BasePlugin:
+    """
+    Tutor plugins are defined by a name and an object that implements one or more of the
+    following properties:
+
+    `config` (dict str->dict(str->str)): contains "add", "defaults", "set" keys. Entries
+    in these dicts will be added or override the global configuration. Keys in "add" and
+    "defaults" will be prefixed by the plugin name in uppercase.
+
+    `patches` (dict str->str): entries in this dict will be used to patch the rendered
+    Tutor templates. For instance, to add "somecontent" to a template that includes '{{
+    patch("mypatch") }}', set: `patches["mypatch"] = "somecontent"`. It is recommended
+    to store all patches in separate files, and to dynamically list patches by listing
+    the contents of a "patches"  subdirectory.
+
+    `templates` (str): path to a directory that includes new template files for the
+    plugin. It is recommended that all files in the template directory are stored in a
+    `myplugin` folder to avoid conflicts with other plugins. Plugin templates are useful
+    for content re-use, e.g: "{% include 'myplugin/mytemplate.html'}".
+
+    `hooks` (dict str->list[str]): hooks are commands that will be run at various points
+    during the lifetime of the platform. For instance, to run `service1` and `service2`
+    in sequence during initialisation, you should define:
+
+        hooks["init"] = ["service1", "service2"]
+
+    It is then assumed that there are `myplugin/hooks/service1/init` and
+    `myplugin/hooks/service2/init` templates in the plugin `templates` directory.
+
+    `command` (click.Command): if a plugin exposes a `command` attribute, users will be able to run it from the command line as `tutor pluginname`.
+    """
+
+    def __init__(self, name: str, loader: t.Optional[t.Any] = None) -> None:
+        self.name = name
+        self.loader = loader
+        self.obj: t.Optional[t.Any] = None
+        self._discover()
+
+    def _discover(self) -> None:
+        # Add itself to the list of installed plugins
+        hooks.Filters.PLUGINS_INSTALLED.add_item(self.name)
+
+        # Add plugin version
+        hooks.Filters.PLUGINS_INFO.add_item((self.name, self._version()))
+
+        # Create actions and filters on load
+        hooks.Actions.PLUGIN_LOADED(self.name).add()(self.__load)
+
+    def __load(self) -> None:
+        """
+        On loading a plugin, we create all the required actions and filters.
+
+        Note that this method is quite costly. Thus it is important that as little is
+        done as part of installing the plugin. For instance, we should not import
+        modules during installation, but only when the plugin is enabled.
+        """
+        # Add all actions/filters
+        self._load_obj()
+        self._load_config()
+        self._load_patches()
+        self._load_tasks()
+        self._load_templates_root()
+        self._load_command()
+
+    def _load_obj(self) -> None:
+        """
+        Override this method to write to the `obj` attribute based on the `loader`.
+        """
+        raise NotImplementedError
+
+    def _load_config(self) -> None:
+        """
+        Load config and check types.
+        """
+        config = get_callable_attr(self.obj, "config", {})
+        if not isinstance(config, dict):
+            raise exceptions.TutorError(
+                f"Invalid config in plugin {self.name}. Expected dict, got {config.__class__}."
+            )
+        for name, subconfig in config.items():
+            if not isinstance(name, str):
+                raise exceptions.TutorError(
+                    f"Invalid config entry '{name}' in plugin {self.name}. Expected str, got {config.__class__}."
+                )
+            if not isinstance(subconfig, dict):
+                raise exceptions.TutorError(
+                    f"Invalid config entry '{name}' in plugin {self.name}. Expected str keys, got {config.__class__}."
+                )
+            for key in subconfig.keys():
+                if not isinstance(key, str):
+                    raise exceptions.TutorError(
+                        f"Invalid config entry '{name}.{key}' in plugin {self.name}. Expected str, got {key.__class__}."
+                    )
+
+        # Config keys in the "add" and "defaults" dicts must be prefixed by
+        # the plugin name, in uppercase.
+        key_prefix = self.name.upper() + "_"
+
+        hooks.Filters.CONFIG_UNIQUE.add_items(
+            [
+                (f"{key_prefix}{key}", value)
+                for key, value in config.get("add", {}).items()
+            ],
+        )
+        hooks.Filters.CONFIG_DEFAULTS.add_items(
+            [
+                (f"{key_prefix}{key}", value)
+                for key, value in config.get("defaults", {}).items()
+            ],
+        )
+        hooks.Filters.CONFIG_OVERRIDES.add_items(
+            [(key, value) for key, value in config.get("set", {}).items()],
+        )
+
+    def _load_patches(self) -> None:
+        """
+        Load patches and check the types are right.
+        """
+        patches = get_callable_attr(self.obj, "patches", {})
+        if not isinstance(patches, dict):
+            raise exceptions.TutorError(
+                f"Invalid patches in plugin {self.name}. Expected dict, got {patches.__class__}."
+            )
+        for patch_name, content in patches.items():
+            if not isinstance(patch_name, str):
+                raise exceptions.TutorError(
+                    f"Invalid patch name '{patch_name}' in plugin {self.name}. Expected str, got {patch_name.__class__}."
+                )
+            if not isinstance(content, str):
+                raise exceptions.TutorError(
+                    f"Invalid patch '{patch_name}' in plugin {self.name}. Expected str, got {content.__class__}."
+                )
+            hooks.Filters.ENV_PATCH(patch_name).add_item(content)
+
+    def _load_tasks(self) -> None:
+        """
+        Load hooks and check types.
+        """
+        tasks = get_callable_attr(self.obj, "hooks", default={})
+        if not isinstance(tasks, dict):
+            raise exceptions.TutorError(
+                f"Invalid hooks in plugin {self.name}. Expected dict, got {tasks.__class__}."
+            )
+
+        build_image_tasks = tasks.get("build-image", {})
+        remote_image_tasks = tasks.get("remote-image", {})
+        pre_init_tasks = tasks.get("pre-init", [])
+        init_tasks = tasks.get("init", [])
+
+        # Build images: hooks = {"build-image": {"myimage": "myimage:latest"}}
+        # We assume that the dockerfile is in the build/myimage folder.
+        for img, tag in build_image_tasks.items():
+            hooks.Filters.IMAGES_BUILD.add_item(
+                (img, ("plugins", self.name, "build", img), tag, []),
+            )
+        # Remote images: hooks = {"remote-image": {"myimage": "myimage:latest"}}
+        for img, tag in remote_image_tasks.items():
+            hooks.Filters.IMAGES_PULL.add_item(
+                (img, tag),
+            )
+            hooks.Filters.IMAGES_PUSH.add_item(
+                (img, tag),
+            )
+        # Pre-init scripts: hooks = {"pre-init": ["myservice1", "myservice2"]}
+        for service in pre_init_tasks:
+            path = (self.name, "hooks", service, "pre-init")
+            hooks.Filters.COMMANDS_PRE_INIT.add_item((service, path))
+        # Init scripts: hooks = {"init": ["myservice1", "myservice2"]}
+        for service in init_tasks:
+            path = (self.name, "hooks", service, "init")
+            hooks.Filters.COMMANDS_INIT.add_item((service, path))
+
+    def _load_templates_root(self) -> None:
+        templates_root = get_callable_attr(self.obj, "templates", default=None)
+        if templates_root is None:
+            return
+        if not isinstance(templates_root, str):
+            raise exceptions.TutorError(
+                f"Invalid templates in plugin {self.name}. Expected str, got {templates_root.__class__}."
+            )
+
+        hooks.Filters.ENV_TEMPLATE_ROOTS.add_item(templates_root)
+        # We only add the "apps" and "build" folders and we render them in the
+        # "plugins/<plugin name>" folder.
+        hooks.filters.add_items(
+            "env:templates:targets",
+            [
+                (
+                    os.path.join(self.name, "apps"),
+                    "plugins",
+                ),
+                (
+                    os.path.join(self.name, "build"),
+                    "plugins",
+                ),
+            ],
+        )
+
+    def _load_command(self) -> None:
+        command = getattr(self.obj, "command", None)
+        if command is None:
+            return
+        if not isinstance(command, click.Command):
+            raise exceptions.TutorError(
+                f"Invalid command in plugin {self.name}. Expected click.Command, got {command.__class__}."
+            )
+        # We force the command name to the plugin name
+        command.name = self.name
+        hooks.Filters.CLI_COMMANDS.add_item(command)
+
+    def _version(self) -> t.Optional[str]:
+        return None
+
+
+class EntrypointPlugin(BasePlugin):
+    """
+    Entrypoint plugins are regular python packages that have a 'tutor.plugin.v0' entrypoint.
+
+    The API for Tutor plugins is currently in development. The entrypoint will switch to
+    'tutor.plugin.v1' once it is stabilised.
+    """
+
+    ENTRYPOINT = "tutor.plugin.v0"
+
+    def __init__(self, entrypoint: pkg_resources.EntryPoint) -> None:
+        self.loader: pkg_resources.EntryPoint
+        super().__init__(entrypoint.name, entrypoint)
+
+    def _load_obj(self) -> None:
+        self.obj = self.loader.load()
+
+    def _version(self) -> t.Optional[str]:
+        if not self.loader.dist:
+            raise exceptions.TutorError(f"Entrypoint plugin '{self.name}' has no dist.")
+        return self.loader.dist.version
+
+    @classmethod
+    def discover_all(cls) -> None:
+        for entrypoint in pkg_resources.iter_entry_points(cls.ENTRYPOINT):
+            try:
+                error: t.Optional[str] = None
+                cls(entrypoint)
+            except pkg_resources.VersionConflict as e:
+                error = e.report()
+            except Exception as e:  # pylint: disable=broad-except
+                error = str(e)
+            if error:
+                fmt.echo_error(
+                    f"Failed to load entrypoint '{entrypoint.name} = {entrypoint.module_name}' from distribution {entrypoint.dist}: {error}"
+                )
+
+
+class OfficialPlugin(BasePlugin):
+    """
+    Official plugins have a "plugin" module which exposes a __version__ attribute.
+    Official plugins should be manually added by instantiating them with: `OfficialPlugin('name')`.
+    """
+
+    NAMES = [
+        "android",
+        "discovery",
+        "ecommerce",
+        "forum",
+        "license",
+        "mfe",
+        "minio",
+        "notes",
+        "richie",
+        "webui",
+        "xqueue",
+    ]
+
+    def _load_obj(self) -> None:
+        self.obj = importlib.import_module(f"tutor{self.name}.plugin")
+
+    def _version(self) -> t.Optional[str]:
+        try:
+            module = importlib.import_module(f"tutor{self.name}.__about__")
+        except ModuleNotFoundError:
+            return None
+        version = getattr(module, "__version__")
+        if version is None:
+            return None
+        if not isinstance(version, str):
+            raise TypeError("OfficialPlugin __version__ must be 'str'")
+        return version
+
+    @classmethod
+    def discover_all(cls) -> None:
+        """
+        This function must be called explicitely from the main. This is to handle
+        detection of official plugins from within the compiled binary. When not running
+        the binary, official plugins are treated as regular entrypoint plugins.
+        """
+        for plugin_name in cls.NAMES:
+            if importlib.util.find_spec(f"tutor{plugin_name}") is not None:
+                OfficialPlugin(plugin_name)
+
+
+class DictPlugin(BasePlugin):
+    def __init__(self, data: Config):
+        self.loader: Config
+        name = data["name"]
+        if not isinstance(name, str):
+            raise exceptions.TutorError(
+                f"Invalid plugin name: '{name}'. Expected str, got {name.__class__}"
+            )
+        super().__init__(name, data)
+
+    def _load_obj(self) -> None:
+        # Create a generic object (sort of a named tuple) which will contain all
+        # key/values from data
+        class Module:
+            pass
+
+        self.obj = Module()
+        for key, value in self.loader.items():
+            setattr(self.obj, key, value)
+
+    def _version(self) -> t.Optional[str]:
+        version = self.loader.get("version", None)
+        if version is None:
+            return None
+        if not isinstance(version, str):
+            raise TypeError("DictPlugin.version must be str")
+        return version
+
+    @classmethod
+    def discover_all(cls) -> None:
+        for path in glob(os.path.join(PLUGINS_ROOT, "*.yml")):
+            with open(path, encoding="utf-8") as f:
+                data = serialize.load(f)
+                if not isinstance(data, dict):
+                    raise exceptions.TutorError(
+                        f"Invalid plugin: {path}. Expected dict."
+                    )
+                try:
+                    cls(data)
+                except KeyError as e:
+                    raise exceptions.TutorError(
+                        f"Invalid plugin: {path}. Missing key: {e.args[0]}"
+                    )
+
+
+@hooks.Actions.CORE_READY.add()
+def _discover_v0_plugins() -> None:
+    """
+    Install all entrypoint and dict plugins.
+
+    Plugins from both classes are discovered in a context, to make it easier to disable
+    them in tests.
+
+    Note that official plugins are not discovered here. That's because they are expected
+    to be discovered manually from within the tutor binary.
+
+    Installing entrypoint or dict plugins can be disabled by defining the
+    ``TUTOR_IGNORE_DICT_PLUGINS`` and ``TUTOR_IGNORE_ENTRYPOINT_PLUGINS``
+    environment variables.
+    """
+    with hooks.Contexts.PLUGINS.enter():
+        if "TUTOR_IGNORE_ENTRYPOINT_PLUGINS" not in os.environ:
+            with hooks.Contexts.PLUGINS_V0_ENTRYPOINT.enter():
+                EntrypointPlugin.discover_all()
+        if "TUTOR_IGNORE_DICT_PLUGINS" not in os.environ:
+            with hooks.Contexts.PLUGINS_V0_YAML.enter():
+                DictPlugin.discover_all()
+
+
+def get_callable_attr(
+    plugin: t.Any, attr_name: str, default: t.Optional[t.Any] = None
+) -> t.Optional[t.Any]:
+    """
+    Return the attribute of a plugin. If this attribute is a callable, return
+    the return value instead.
+    """
+    attr = getattr(plugin, attr_name, default)
+    if callable(attr):
+        attr = attr()  # pylint: disable=not-callable
+    return attr

tutor/plugins/v1.py

@@ -0,0 +1,76 @@
+import importlib.util
+import os
+from glob import glob
+
+import pkg_resources
+
+from tutor import hooks
+
+from .base import PLUGINS_ROOT
+
+
+@hooks.Actions.CORE_READY.add()
+def _discover_module_plugins() -> None:
+    """
+    Discover .py files in the plugins root folder.
+    """
+    with hooks.Contexts.PLUGINS.enter():
+        for path in glob(os.path.join(PLUGINS_ROOT, "*.py")):
+            discover_module(path)
+
+
+@hooks.Actions.CORE_READY.add()
+def _discover_entrypoint_plugins() -> None:
+    """
+    Discover all plugins that declare a "tutor.plugin.v1" entrypoint.
+    """
+    with hooks.Contexts.PLUGINS.enter():
+        for entrypoint in pkg_resources.iter_entry_points("tutor.plugin.v1"):
+            discover_package(entrypoint)
+
+
+def discover_module(path: str) -> None:
+    """
+    Install a plugin written as a single file module.
+    """
+    name = os.path.splitext(os.path.basename(path))[0]
+
+    # Add plugin to the list of installed plugins
+    hooks.Filters.PLUGINS_INSTALLED.add_item(name)
+
+    # Add plugin information
+    hooks.Filters.PLUGINS_INFO.add_item((name, path))
+
+    # Import module on enable
+    load_plugin_action = hooks.Actions.PLUGIN_LOADED(name)
+
+    @load_plugin_action.add()
+    def load() -> None:
+        # https://docs.python.org/3/library/importlib.html#importing-a-source-file-directly
+        spec = importlib.util.spec_from_file_location("tutor.plugin.v1.{name}", path)
+        if spec is None or spec.loader is None:
+            raise ValueError("Plugin could not be found: {path}")
+        module = importlib.util.module_from_spec(spec)
+        spec.loader.exec_module(module)
+
+
+def discover_package(entrypoint: pkg_resources.EntryPoint) -> None:
+    """
+    Install a plugin from a python package.
+    """
+    name = entrypoint.name
+
+    # Add plugin to the list of installed plugins
+    hooks.Filters.PLUGINS_INSTALLED.add_item(name)
+
+    # Add plugin information
+    if entrypoint.dist is None:
+        raise ValueError(f"Could not read plugin version: {name}")
+    hooks.Filters.PLUGINS_INFO.add_item((name, entrypoint.dist.version))
+
+    # Import module on enable
+    load_plugin_action = hooks.Actions.PLUGIN_LOADED(name)
+
+    @load_plugin_action.add()
+    def load() -> None:
+        entrypoint.load()

tutor/types.py

@@ -1,39 +1,45 @@
-from typing import Any, Dict, List, Optional, Type, TypeVar, Union
+import typing as t
+
+# https://mypy.readthedocs.io/en/latest/kinds_of_types.html#type-aliases
+from typing_extensions import TypeAlias
 
 from . import exceptions
 
-ConfigValue = Union[
-    str, float, None, bool, List[str], List[Any], Dict[str, Any], Dict[Any, Any]
+ConfigValue: TypeAlias = t.Union[
+    str,
+    float,
+    None,
+    bool,
+    t.List[str],
+    t.List[t.Any],
+    t.Dict[str, t.Any],
+    t.Dict[t.Any, t.Any],
 ]
-Config = Dict[str, ConfigValue]
+Config: TypeAlias = t.Dict[str, ConfigValue]
 
 
-def cast_config(config: Any) -> Config:
+def cast_config(config: t.Any) -> Config:
     if not isinstance(config, dict):
         raise exceptions.TutorError(
-            "Invalid configuration: expected dict, got {}".format(config.__class__)
+            f"Invalid configuration: expected dict, got {config.__class__}"
         )
     for key in config.keys():
         if not isinstance(key, str):
             raise exceptions.TutorError(
-                "Invalid configuration: expected str, got {} for key '{}'".format(
-                    key.__class__, key
-                )
+                f"Invalid configuration: expected str, got {key.__class__} for key '{key}'"
             )
     return config
 
 
-T = TypeVar("T")
+T = t.TypeVar("T")
 
 
 def get_typed(
-    config: Config, key: str, expected_type: Type[T], default: Optional[T] = None
+    config: Config, key: str, expected_type: t.Type[T], default: t.Optional[T] = None
 ) -> T:
     value = config.get(key, default)
     if not isinstance(value, expected_type):
         raise exceptions.TutorError(
-            "Invalid config entry: expected {}, got {} for key '{}'".format(
-                expected_type.__name__, value.__class__, key
-            )
+            "Invalid config entry: expected {expected_type.__name__}, got {value.__class__} for key '{key}'"
         )
     return value