fix(python): Read venv prompt from pyvenv.cfg (#1747)

* ✨ Add  --prompt rendering to python virtualenv

* Use pyvenv.cfg to find prompt

* Remove usage of VIRTUAL_ENV_PROMPT variable

Seeing how both venv and virtualenv set a pyvenv.cfg, this isn't needed.
Additionally pyvenv.cfg is set in earlier versions than VIRTUAL_ENV_PROMPT,
which at this moment is in the unrelased python 3.10

* Smarter result unwrapping thanks to clippy

Cargo.lock

@@ -1,5 +1,11 @@
 # This file is automatically @generated by Cargo.
 # It is not intended for manual editing.
+[[package]]
+name = "ahash"
+version = "0.4.5"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "0adac150c2dd5a9c864d054e07bda5e6bc010cd10036ea5f17e82a2f5867f735"
+
 [[package]]
 name = "aho-corasick"
 version = "0.7.13"
@@ -333,6 +339,15 @@ dependencies = [
  "winapi",
 ]
 
+[[package]]
+name = "dlv-list"
+version = "0.2.2"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "1b391911b9a786312a10cb9d2b3d0735adfd5a8113eb3648de26a75e91b0826c"
+dependencies = [
+ "rand",
+]
+
 [[package]]
 name = "doc-comment"
 version = "0.3.3"
@@ -430,6 +445,15 @@ dependencies = [
  "autocfg",
 ]
 
+[[package]]
+name = "hashbrown"
+version = "0.9.1"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "d7afe4a420e3fe79967a00898cc1f4db7c8a49a9333a29f8a4bd76a253d5cd04"
+dependencies = [
+ "ahash",
+]
+
 [[package]]
 name = "hermit-abi"
 version = "0.1.15"
@@ -468,7 +492,7 @@ source = "registry+https://github.com/rust-lang/crates.io-index"
 checksum = "86b45e59b16c76b11bf9738fd5d38879d3bd28ad292d7b313608becb17ae2df9"
 dependencies = [
  "autocfg",
- "hashbrown",
+ "hashbrown 0.8.2",
 ]
 
 [[package]]
@@ -787,6 +811,16 @@ dependencies = [
  "vcpkg",
 ]
 
+[[package]]
+name = "ordered-multimap"
+version = "0.3.0"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "87a6df8506c2d359d5105344891f283e8e7ef81a7c6a542d516f8707e4a09b6b"
+dependencies = [
+ "dlv-list",
+ "hashbrown 0.9.1",
+]
+
 [[package]]
 name = "os_info"
 version = "3.0.0"
@@ -1020,6 +1054,16 @@ dependencies = [
  "crossbeam-utils",
 ]
 
+[[package]]
+name = "rust-ini"
+version = "0.16.0"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "dcdbf249a931ceb503aa80e08ca016675dbc7884eda8e2d88e85533d4dbade62"
+dependencies = [
+ "cfg-if",
+ "ordered-multimap",
+]
+
 [[package]]
 name = "ryu"
 version = "1.0.5"
@@ -1153,6 +1197,7 @@ dependencies = [
  "rand",
  "rayon",
  "regex",
+ "rust-ini",
  "serde_json",
  "shell-words",
  "starship_module_config_derive",

Cargo.toml

@@ -33,6 +33,7 @@ ansi_term = "0.12.1"
 dirs-next = "1.0.1"
 git2 = { version = "0.13.11", default-features = false }
 toml = { version = "0.5.6", features = ["preserve_order"] }
+rust-ini = "0.16" 
 serde_json = "1.0.58"
 rayon = "1.4.1"
 log = { version = "0.4.11", features = ["std"] }

src/modules/python.rs

@@ -1,3 +1,4 @@
+use ini::Ini;
 use std::path::Path;
 
 use super::{Context, Module, RootModuleConfig};
@@ -109,19 +110,29 @@ fn format_python_version(python_stdout: &str) -> String {
 
 fn get_python_virtual_env(context: &Context) -> Option<String> {
     context.get_env("VIRTUAL_ENV").and_then(|venv| {
-        Path::new(&venv)
+        get_prompt_from_venv(Path::new(&venv)).or_else(|| {
-            .file_name()
+            Path::new(&venv)
-            .map(|filename| String::from(filename.to_str().unwrap_or("")))
+                .file_name()
+                .map(|filename| String::from(filename.to_str().unwrap_or("")))
+        })
     })
 }
+fn get_prompt_from_venv(venv_path: &Path) -> Option<String> {
+    Ini::load_from_file(venv_path.join("pyvenv.cfg"))
+        .ok()?
+        .general_section()
+        .get("prompt")
+        .map(String::from)
+}
 
 #[cfg(test)]
 mod tests {
     use super::*;
     use crate::test::ModuleRenderer;
     use ansi_term::Color;
-    use std::fs::File;
+    use std::fs::{create_dir_all, File};
     use std::io;
+    use std::io::Write;
 
     #[test]
     fn test_format_python_version() {
@@ -317,6 +328,33 @@ mod tests {
         dir.close()
     }
 
+    #[test]
+    fn with_active_venv_and_prompt() -> io::Result<()> {
+        let dir = tempfile::tempdir()?;
+        create_dir_all(dir.path().join("my_venv"))?;
+        let mut venv_cfg = File::create(dir.path().join("my_venv").join("pyvenv.cfg"))?;
+        venv_cfg.write_all(
+            br#"
+home = something
+prompt = 'foo' 
+        "#,
+        )?;
+        venv_cfg.sync_all()?;
+
+        let actual = ModuleRenderer::new("python")
+            .path(dir.path())
+            .env("VIRTUAL_ENV", dir.path().join("my_venv").to_str().unwrap())
+            .collect();
+
+        let expected = Some(format!(
+            "via {} ",
+            Color::Yellow.bold().paint("🐍 v2.7.17 (foo)")
+        ));
+
+        assert_eq!(actual, expected);
+        dir.close()
+    }
+
     fn check_python2_renders(dir: &tempfile::TempDir, starship_config: Option<toml::Value>) {
         let config = starship_config.unwrap_or(toml::toml! {
             [python]