Path-only pythonProjects entries crash manager initialization

[atomiechen]

Environment data

• Python Environments extension version: 1.36.0 (latest Marketplace stable); also reproduced from main at f61acdf535b9c8e8983e6b600048f3f4de1425e1 (package version 1.37.0)
• Python extension (ms-python.python) version: 2026.4.0
• VS Code version (Help → About): 1.130.0 (1b6a188127eeaf9194f945eb6eb89a657e93c54c)
• OS and version: macOS 15.3.2 arm64
• Python version: 3.9.6
• Environment manager in use: venv
• Shell: zsh
• Remote / container scenario: none
• Workspace type: single-folder mono-repo
• Is this a regression? Unknown

Repro Steps

1. Start VS Code with empty --user-data-dir and --extensions-dir directories.

2. Install only ms-python.python and ms-python.vscode-pylance; this installs ms-python.vscode-python-envs as a dependency.

3. Open a fresh folder containing backend/main.py and backend/.venv.

4. Add the following workspace settings:

   {
       "python.useEnvironmentsExtension": true,
       "python.analysis.usePerProjectEnvironments": true,
       "python-envs.pythonProjects": [
           {
               "path": "backend"
           }
       ]
   }

5. Reload the window and open backend/main.py.

Expected behavior

The path-only project entry is accepted. Because envManager and packageManager are optional in the contributed setting schema, the extension uses python-envs.defaultEnvManager and python-envs.defaultPackageManager.

Actual behavior

Environment-manager initialization repeatedly throws TypeError: Cannot read properties of undefined (reading 'length'). The Python extension can consequently report an activation failure, and per-project interpreter/Pylance integration is unreliable.

getDefaultEnvManagerSetting() and getDefaultPkgManagerSetting() dereference optional object properties without checking whether they exist:

if (settings && settings.envManager.length > 0) {
// ...
if (settings && settings.packageManager.length > 0) {

Explicitly adding both manager properties avoids the exception, but duplicates defaults that the setting schema already defines and should not be required.

Logs

Python-envs extension version: 1.36.0
Post-initialization tasks failed: TypeError: Cannot read properties of undefined (reading 'length')
    at getDefaultEnvManagerSetting (.../ms-python.vscode-python-envs-1.36.0-darwin-arm64/dist/extension.js:2:389988)
    at sendManagerSelectionTelemetry (.../dist/extension.js:2:286259)

TypeError: Cannot read properties of undefined (reading 'length')
    at getDefaultEnvManagerSetting (.../ms-python.vscode-python-envs-1.36.0-darwin-arm64/dist/extension.js:2:389988)
    at waitForEnvManager (.../dist/extension.js:2:313554)
    at async getEnvironment (.../dist/extension.js:2:384509)

Additional context

The reproduction used a genuinely empty VS Code profile with no third-party extensions or pre-existing user settings.

A local fix that treats omitted manager properties as fallback-to-default values removes the runtime errors in a second fresh profile. It also passes the complete unit-test suite (1,429 passing) and lint.

AI disclosure: Prepared with assistance from OpenAI Codex.