v0.2.0: Comprehensive Web App Debugging Support

Release v0.2.0: Comprehensive Web App Debugging Support

🎉 Major Features

Full Web Application Debugging

• HTTP-triggered breakpoints for Flask, Django, and FastAPI applications
• Launch web servers under debugger control with dap_launch
• Pause execution on HTTP requests and inspect request handlers interactively
• Complete automated test suite demonstrating the workflow

New Examples & Documentation

• examples/web_flask/run_flask.py - Flask app launcher for debugging
• tests/test_web_app_debug.py - Comprehensive automated tests (2 tests, both passing)
• docs/DEBUGGING_WEB_APPS.md - Complete guide for web app debugging
• Enhanced AI agent instructions in agent_instructions.md

⚠️ Breaking Changes

Removed dap_attach()

The dap_attach approach was investigated but does not work with debugpy. When you run python -m debugpy --listen, debugpy does not respond to DAP attach requests. This is a fundamental limitation of debugpy's architecture.

Migration: Use dap_launch for ALL debugging scenarios:

• ✅ Web servers (Flask/Django/FastAPI)
• ✅ GUI applications
• ✅ Command-line scripts
• ✅ Long-running processes

✨ What's New

Files Added

• examples/web_flask/run_flask.py - Flask debugging launcher
• examples/gui_counter/run_counter_debug.py - GUI counter launcher
• tests/test_web_app_debug.py - Automated web app debugging tests
• docs/DEBUGGING_WEB_APPS.md - Comprehensive debugging guide
• .envrc - Auto-activate venv with direnv

Documentation Updates

• agent_instructions.md: Added "Debugging Web Applications" section with step-by-step workflow
• docs/mcp_usage.md: Updated with web app debugging examples
• examples/web_flask/README.md: Complete rewrite with correct dap_launch workflow
• examples/gui_counter/README.md: Added GUI debugging instructions

🔧 Improvements

Code Quality

• Removed 187 lines of non-functional dap_attach code
• Removed DirectDAPClient class and all attach mode logic
• Fixed all ruff, black, and mypy linting issues
• Added types-aiofiles for proper type checking
• Better error handling and type safety

Testing

• 9/9 tests passing (up from 7)
• 2 new web app debugging tests
• Tests verify HTTP-triggered breakpoints and loop iteration debugging

Developer Experience

• .envrc for automatic venv activation with direnv
• VSCode settings configured to use .venv by default
• Improved pre-commit hooks (exclude examples from mypy)

📊 Test Results

tests/test_cli.py::test_cli_help_returns_zero PASSED
tests/test_mcp_end_to_end.py::test_mcp_end_to_end PASSED  
tests/test_mcp_server.py::test_dap_launch_handles_late_initialized PASSED
tests/test_mcp_server.py::test_dap_set_breakpoints_reuses_session PASSED
tests/test_mcp_server.py::test_dap_locals_and_continue PASSED
tests/test_mcp_server.py::test_dap_shutdown_closes_session PASSED
tests/test_mcp_server.py::test_dap_launch_breakpoints_by_source_retry_after_stop PASSED
tests/test_web_app_debug.py::test_flask_app_debugging_with_http_breakpoint PASSED
tests/test_web_app_debug.py::test_flask_breakpoint_hit_twice_in_loop PASSED

============================== 9 passed in 45.57s ==============================

🚀 Getting Started with Web App Debugging

1. Launch your Flask app under debugger control:

from mcp_server import dap_launch

await dap_launch(
    program="examples/web_flask/run_flask.py",
    breakpoints_by_source={
        "examples/web_flask/inventory.py": [18]
    },
    wait_for_breakpoint=False
)

2. Trigger the breakpoint:

curl http://127.0.0.1:5001/total

3. Inspect variables and step through code:

await dap_wait_for_event("stopped")
locals_result = await dap_locals()
await dap_step_over()
await dap_continue()

See docs/DEBUGGING_WEB_APPS.md for complete details!

🙏 Acknowledgments

This release represents a major step forward in making Python debugging more accessible to AI agents and developers. Special thanks to the debugpy and MCP communities!

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Full Changelog: v0.1.1...v0.2.0