SIGN IN SIGN UP

The official Python SDK for Model Context Protocol servers and clients

22500 0 0 Python
# Development Guidelines
2025-01-03 15:26:25 +00:00
This document contains critical information about working with this codebase. Follow these guidelines precisely.
2025-01-03 15:26:25 +00:00
## Core Development Rules
2025-01-03 15:26:25 +00:00
1. Package Management
- ONLY use uv, NEVER pip
- Installation: `uv add package`
- Running tools: `uv run tool`
- Upgrading: `uv add --dev package --upgrade-package package`
- FORBIDDEN: `uv pip install`, `@latest` syntax
2025-01-03 15:26:25 +00:00
2. Code Quality
- Type hints required for all code
- Public APIs must have docstrings
- Functions must be focused and small
- Follow existing patterns exactly
2025-07-09 11:15:14 +01:00
- Line length: 120 chars maximum
2025-01-03 15:26:25 +00:00
3. Testing Requirements
- Framework: `uv run --frozen pytest`
- Async testing: use anyio, not asyncio
- Coverage: test edge cases and errors
- New features require tests
- Bug fixes require regression tests
- Avoid `anyio.sleep()` with a fixed duration to wait for async operations. Instead:
- Use `anyio.Event` — set it in the callback/handler, `await event.wait()` in the test
- For stream messages, use `await stream.receive()` instead of `sleep()` + `receive_nowait()`
- Exception: `sleep()` is appropriate when testing time-based features (e.g., timeouts)
- Wrap indefinite waits (`event.wait()`, `stream.receive()`) in `anyio.fail_after(5)` to prevent hangs
2025-01-03 15:26:25 +00:00
- For commits fixing bugs or adding features based on user reports add:
```bash
git commit --trailer "Reported-by:<name>"
```
Where `<name>` is the name of the user.
- For commits related to a Github issue, add
```bash
git commit --trailer "Github-Issue:#<number>"
```
- NEVER ever mention a `co-authored-by` or similar aspects. In particular, never
mention the tool used to create the commit message or PR.
## Pull Requests
- Create a detailed message of what changed. Focus on the high level description of
the problem it tries to solve, and how it is solved. Don't go into the specifics of the
code unless it adds clarity.
- NEVER ever mention a `co-authored-by` or similar aspects. In particular, never
mention the tool used to create the commit message or PR.
## Python Tools
2025-01-03 15:26:25 +00:00
## Code Formatting
2025-01-03 15:26:25 +00:00
1. Ruff
- Format: `uv run --frozen ruff format .`
- Check: `uv run --frozen ruff check .`
- Fix: `uv run --frozen ruff check . --fix`
- Critical issues:
- Line length (88 chars)
- Import sorting (I001)
- Unused imports
- Line wrapping:
- Strings: use parentheses
- Function calls: multi-line with proper indent
- Imports: split into multiple lines
2025-01-03 15:26:25 +00:00
2. Type Checking
- Tool: `uv run --frozen pyright`
- Requirements:
- Explicit None checks for Optional
- Type narrowing for strings
- Version warnings can be ignored if checks pass
3. Pre-commit
- Config: `.pre-commit-config.yaml`
- Runs: on git commit
- Tools: Prettier (YAML/JSON), Ruff (Python)
- Ruff updates:
- Check PyPI versions
- Update config rev
- Commit config first
## Error Resolution
2025-01-03 15:26:25 +00:00
1. CI Failures
- Fix order:
1. Formatting
2. Type errors
3. Linting
- Type errors:
- Get full line context
- Check Optional types
- Add type narrowing
- Verify function signatures
2. Common Issues
- Line length:
- Break strings with parentheses
- Multi-line function calls
- Split imports
- Types:
- Add None checks
- Narrow string types
- Match existing patterns
- Pytest:
- If the tests aren't finding the anyio pytest mark, try adding PYTEST_DISABLE_PLUGIN_AUTOLOAD=""
to the start of the pytest run command eg:
`PYTEST_DISABLE_PLUGIN_AUTOLOAD="" uv run --frozen pytest`
3. Best Practices
- Check git status before commits
- Run formatters before type checks
- Keep changes minimal
- Follow existing patterns
- Document public APIs
- Test thoroughly
2025-07-09 11:15:14 +01:00
## Exception Handling
- **Always use `logger.exception()` instead of `logger.error()` when catching exceptions**
- Don't include the exception in the message: `logger.exception("Failed")` not `logger.exception(f"Failed: {e}")`
- **Catch specific exceptions** where possible:
- File ops: `except (OSError, PermissionError):`
- JSON: `except json.JSONDecodeError:`
- Network: `except (ConnectionError, TimeoutError):`
- **Only catch `Exception` for**:
- Top-level handlers that must not crash
- Cleanup blocks (log at debug level)