From 731de6a747542298b5a847751ec8ce651e667d14 Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?R=C3=A9gis=20Behmo?= <regis@behmo.com>
Date: Tue, 21 Jan 2020 17:09:58 +0100
Subject: [PATCH] Fix incorrectly parsed empty strings in `config save --set
 ...=...`

When running `config save --set KEY=""`, KEY was incorrectly interpreted
as null.
---
 CHANGELOG.md             | 4 ++++
 tests/test_serialize.py  | 8 ++++++++
 tutor/commands/config.py | 5 +++++
 tutor/serialize.py       | 6 +++++-
 4 files changed, 22 insertions(+), 1 deletion(-)

diff --git a/CHANGELOG.md b/CHANGELOG.md
index f7371ba..5a98211 100644
--- a/CHANGELOG.md
+++ b/CHANGELOG.md
@@ -2,6 +2,10 @@
 
 Note: Breaking changes between versions are indicated by "💥".
 
+## Unreleased
+
+- [Bugfix] Fix incorrectly parsed empty strings for `config save --set ...=...` commands
+
 ## 3.11.2 (2020-01-17)
 
 - [Bugfix] Make sure `docker-compose.override.yml` are loaded in dev and local contexts
diff --git a/tests/test_serialize.py b/tests/test_serialize.py
index 0534b79..3a78d26 100644
--- a/tests/test_serialize.py
+++ b/tests/test_serialize.py
@@ -25,3 +25,11 @@ class SerializeTests(unittest.TestCase):
 
     def test_parse_weird_chars(self):
         self.assertEqual("*@google.com", serialize.parse("*@google.com"))
+
+    def test_parse_empty_string(self):
+        self.assertEqual("", serialize.parse("''"))
+
+    # def test_dump_null(self):#     # Unfortunately, this fails as the output is "null\n...\n"
+
+
+#     self.assertEqual("null", serialize.dumps(None))
diff --git a/tutor/commands/config.py b/tutor/commands/config.py
index fe74bab..f55ad13 100644
--- a/tutor/commands/config.py
+++ b/tutor/commands/config.py
@@ -25,6 +25,10 @@ class YamlParamType(click.ParamType):
             k, v = value.split("=")
         except ValueError:
             self.fail("'{}' is not of the form 'key=value'.".format(value), param, ctx)
+        if not v:
+            # Empty strings are incorrectly interpreted as null values, which is
+            # incorrect.
+            v = "''"
         return k, serialize.parse(v)
 
 
@@ -93,6 +97,7 @@ def printroot(context):
 def printvalue(context, key):
     config = tutor_config.load(context.root)
     try:
+        # Note that this will incorrectly print None values
         fmt.echo(config[key])
     except KeyError:
         raise exceptions.TutorError("Missing configuration value: {}".format(key))
diff --git a/tutor/serialize.py b/tutor/serialize.py
index ca6c3b7..99a29da 100644
--- a/tutor/serialize.py
+++ b/tutor/serialize.py
@@ -8,7 +8,11 @@ def load(stream):
 
 
 def dump(content, fileobj):
-    yaml.dump(content, fileobj, default_flow_style=False)
+    yaml.dump(content, stream=fileobj, default_flow_style=False)
+
+
+def dumps(content):
+    return yaml.dump(content, stream=None, default_flow_style=False)
 
 
 def parse(v):