Add comprehensive tests for resolveAndUpdatePythonPath prioritization logic

[Copilot]

Overview

This PR adds 24 comprehensive tests for the resolveAndUpdatePythonPath function to validate its prioritization logic, enabling safe refactoring of this complex code path.

Background

The resolveAndUpdatePythonPath function handles the resolution and prioritization of multiple Python path configuration fields (pythonPath, python, debugAdapterPython, debugLauncherPython) with complex fallback behavior. While existing tests covered basic scenarios, there was insufficient coverage of the prioritization rules when multiple fields are set to different values.

What This PR Adds

1. Python Path and Python Field Interaction (8 tests)

Tests that validate the prioritization when both pythonPath (deprecated) and python fields are set:

// Example: When both are concrete paths, python takes precedence
const config = {
    pythonPath: '/path/to/pythonPath/python',
    python: '/path/to/python/python'
};
// Result: config.python === '/path/to/python/python'

Covers scenarios including:

• pythonPath concrete + python undefined → python inherits from pythonPath
• pythonPath concrete + python concrete → python takes precedence
• pythonPath ${command:python.interpreterPath} + python concrete → python takes precedence
• Both set to ${command:python.interpreterPath} → both resolve to interpreter

2. Debug Adapter/Launcher Python Prioritization (8 tests)

Tests that validate fallback behavior for debugAdapterPython and debugLauncherPython:

// Example: Explicit values take precedence over defaults
const config = {
    python: '/path/to/python',
    debugAdapterPython: '/path/to/debugAdapter/python'
};
// Result: Each field maintains its explicit value

Validates:

• Fallback to pythonPath ?? python when undefined
• Explicitly set values take precedence
• Complex scenarios with all three fields set differently

3. PythonPathSource Tracking (6 tests)

New tests for the pythonPathSource field that tracks whether the Python path came from launch.json (explicit) or settings.json (resolved):

// Example: Explicit python path sets source to launchJson
const config = { python: '/explicit/path' };
// Result: pythonPathSource === PythonPathSource.launchJson

// Example: Resolved from interpreter sets source to settingsJson
const config = { python: '${command:python.interpreterPath}' };
// Result: pythonPathSource === PythonPathSource.settingsJson

4. Edge Cases (2 tests)

• Empty string handling for pythonPath
• Complex multi-field scenarios with all four fields set

Test Infrastructure Enhancements

• Added getPythonPathSource() method to test class for verifying source tracking
• Imported PythonPathSource enum for proper type-safe assertions
• Organized tests in dedicated suite: "resolveAndUpdatePythonPath prioritization tests"
• All tests use proper sinon mocking for getInterpreterDetails

Why This Matters

1. Refactoring Safety: These tests ensure that any refactoring of the prioritization logic maintains exact behavioral compatibility
2. Documentation: Tests serve as executable documentation of the complex prioritization rules
3. Backward Compatibility: Validates that the deprecated pythonPath field continues to work correctly during the transition period
4. Source Tracking: Ensures telemetry and debugging tools can correctly identify the source of Python paths

Testing

• ✅ All tests compile successfully (TypeScript)
• ✅ ESLint passes with no errors
• ✅ Code review found no issues
• ✅ CodeQL security scan passed

Files Changed

• src/test/unittest/configuration/resolvers/base.unit.test.ts (+355 lines)

Warning

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Original prompt

add tests for resolveAndUpdatePythonPath so I can test a refactoring of this code. Specifically want to test prioritization of the different things when set

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