Python Script Executor

Part of #7435 — Multi-Language Hook Support

User Story

As a template consumer running azd up on a Python-based template, I want Python hook scripts to automatically install their dependencies and execute correctly so I don't need to manually set up virtual environments or run pip install.

Solution Approach

Create pkg/tools/language/python_executor.go (NEW):

type pythonExecutor struct {
    pythonCli     *python.Cli
    commandRunner exec.CommandRunner
    console       input.Console
    projectRoot   string
}

Prepare(ctx, scriptPath) method:

1. Check runtime: pythonCli.CheckInstalled(ctx) → hard error with ErrorWithSuggestion + pythonCli.InstallUrl() if missing.
2. Discover project: DiscoverProjectFile(filepath.Dir(scriptPath), projectRoot, PythonProjectFiles).
3. No project file found → skip venv and dependency install (standalone script is valid).
4. Project file found:
   • Create .venv in project dir if not exists via pythonCli.CreateVirtualEnv().
   • If pyproject.toml exists → pythonCli.InstallProject().
   • Else if requirements.txt exists → pythonCli.InstallRequirements().
   • Store projectDir and venvName for Execute().

Execute(ctx, scriptPath, options) method:

• With venv: pythonCli.Run(ctx, projectDir, ".venv", envVars, scriptPath).
• Standalone: construct exec.RunArgs with python scriptPath, execute via commandRunner.Run().
• Environment variables from hook options passed through to Python process.
• options.Interactive controls stdin attachment.

Create pkg/tools/language/python_executor_test.go (NEW) — mock CommandRunner:

1. Prepare — runtime not installed → error with install suggestion
2. Prepare — with requirements.txt → venv + install called
3. Prepare — with pyproject.toml → venv + InstallProject called
4. Prepare — both files → pyproject.toml preferred
5. Prepare — standalone (no project files) → no venv, no install
6. Prepare — venv already exists → skip CreateVirtualEnv, still run install (idempotent)
7. Execute — with venv → python.Cli.Run() called correctly
8. Execute — standalone → Python called directly
9. Execute — env vars passed through

Files: pkg/tools/language/python_executor.go (NEW), pkg/tools/language/python_executor_test.go (NEW)

Acceptance Criteria

• All unit tests pass
• Missing Python runtime → clear, actionable error message with install URL
• Dependencies installed before script execution
• Virtual environment created in project directory (not temp)
• Standalone scripts (no requirements.txt/pyproject.toml) work without venv
• Reuses existing python.Cli methods — no reimplementation of venv activation

References

• Refs: Contributes to A standard or better way to populate local environments with azd env variables #4384; Motivated by Hooks analysis and learning #3978
• Contributes to: Multi-Language Hook Support: Python, JavaScript, TypeScript, .NET #7435