posthog/CLAUDE.md

PostHog Development Guide

Commands

• Tests:
  • All tests: pytest
  • Single test: pytest path/to/test.py::TestClass::test_method
  • Frontend: cd frontend && pnpm test
  • Single frontend test: cd frontend && pnpm jest <test_file>
• Lint:
  • Python: ruff .
  • Frontend: cd frontend && pnpm format
  • TypeScript check: cd frontend && pnpm typescript:check
• Build:
  • Frontend: cd frontend && pnpm build
  • Start dev: ./bin/start

Code Style

• Python: Use type hints, follow mypy strict rules
• Frontend: TypeScript required, explicit return types
• Imports: Use simple-import-sort, avoid direct dayjs imports (use lib/dayjs)
• Components: Use Lemon components (LemonButton, LemonInput, etc.) not antd
• CSS: Use utility classes instead of inline styles
• Error handling: Prefer explicit error handling with typed errors
• Naming: Use descriptive names, camelCase for JS/TS, snake_case for Python
• Comments: Leave comments to explain tricky areas of the code or to explain WHY something is there, but don't just leave comments everywhere, the code should be default readable