Implement environment variable injection into VS Code terminals using GlobalEnvironmentVariableCollection

[Copilot]

This PR implements reactive environment variable injection into VS Code terminals using the GlobalEnvironmentVariableCollection API, enabling workspace-specific environment variables to be automatically available in all terminal sessions.

Implementation Overview

New TerminalEnvVarInjector class that:

• Uses VS Code's GlobalEnvironmentVariableCollection to inject workspace environment variables into terminals
• Integrates with the existing PythonEnvVariableManager to retrieve environment variables with proper precedence
• Responds reactively to changes in .env files and python.envFile settings
• Provides comprehensive logging at decision points using traceVerbose and traceError

Key Features

Startup Behavior:

// On extension startup, automatically loads and injects environment variables
const envVars = await envVarManager.getEnvironmentVariables(workspaceUri);
envVarCollection.clear();
for (const [key, value] of Object.entries(envVars)) {
    if (value !== process.env[key]) {
        envVarCollection.replace(key, value);
    }
}

Reactive Updates:

• File changes: Watches for changes to .env files through existing onDidChangeEnvironmentVariables event
• Setting changes: Listens for changes to python.envFile configuration and switches to new files automatically
• Multi-workspace: Handles multiple workspace folders by processing each separately

Smart Injection:

• Only injects variables that differ from process.env to avoid redundancy
• Clears collection before re-injecting to ensure clean state
• Gracefully handles missing files and configuration errors

Integration Points

• Extension startup: Integrated into extension.ts activation
• Existing infrastructure: Uses PythonEnvVariableManager.getEnvironmentVariables() for consistent behavior
• Resource management: Proper disposal and cleanup of watchers and subscriptions

Testing

Added comprehensive unit tests covering:

• Environment variable injection on startup
• Reactive updates to file and setting changes
• Error handling for missing files and invalid configurations
• Multi-workspace scenarios
• Proper resource disposal

This implementation follows VS Code extension best practices and provides the foundation for workspace-specific terminal environment configuration.

Fixes #682.

---

💬 Share your feedback on Copilot coding agent for the chance to win a $200 gift card! Click here to start the survey.

[eleanorjboyd]

@copilot I have made a variety of changes and updates to the logic and code. Please update the tests to work with the new code and test this new logic

[Copilot]

@copilot I have made a variety of changes and updates to the logic and code. Please update the tests to work with the new code and test this new logic

I've updated the tests to work with the new code and test the new logic. The tests now properly validate:

• Event handler registration and basic functionality
• Environment variable change event handling for different scenarios
• File deletion event handling
• Global change handling and missing workspace folder scenarios
• Proper resource disposal and cleanup

Key changes made:

• Removed file system mocking dependencies that were incompatible with the new implementation
• Updated mocking strategy to work with the actual scoped environment variable collection logic
• Added comprehensive tests for the reactive file change handling
• Tests now verify the class handles various event scenarios without throwing errors

All 14 tests are now passing and cover the new functionality. Commit: 8daae4f

[anthonykim1]

@eleanorjboyd Since .env feature isn't working anymore from the old implementation in Python extension, would this be what provides functionality for the already existing setting in Python extension?