Code Quality Gate

5-Stage Quality Pipeline

Before ANY commit, code must pass ALL stages. No exceptions.

Stage 1: Code Formatting (Ruff Format)

poetry run ruff format .

What it checks:

• Consistent code style (PEP 8 compliant)
• Line length (88 characters by default)
• Imports formatting
• Trailing whitespace

Action: Auto-fixes issues. Re-run if changes were made.

Stage 2: Linting (Ruff Check)

poetry run ruff check . --fix

What it checks:

• Unused imports and variables
• Code smells and anti-patterns
• Security issues (hardcoded secrets, SQL injection)
• Complexity issues
• Missing docstrings

Action: Auto-fixes when possible. Manual fixes required for some issues.

Stage 3: Type Checking (MyPy) - Optional

poetry run mypy app/ --ignore-missing-imports || true

What it checks:

• Type hint correctness
• Return type mismatches
• Argument type errors
• None-safety violations

Action: Fix type errors. Use # type: ignore only as last resort with comment explaining why.

Stage 4: Tests (Pytest)

poetry run pytest tests/ -v --maxfail=1

What it checks:

• All tests pass
• No test failures
• No test errors

Action: Fix failing tests. Never skip tests.

Stage 5: Import Sorting

poetry run ruff check . --select I --fix

What it checks:

• Import order (stdlib → third-party → local)
• Import grouping
• Unused imports

Action: Auto-fixes import order.

Full Quality Gate Command

Run all stages in sequence:

poetry run ruff format . && \
poetry run ruff check . --fix && \
poetry run pytest tests/ -v && \
echo "✅ All quality checks passed!"

When to Run Quality Gates

1. Before Every Commit

# Before git commit
./run_quality_gate.sh
git add .
git commit -m "feat: add user endpoint"

2. After Major Refactoring

# After large code changes
poetry run pytest tests/ -v --cov=app --cov-report=html

3. Before Pull Request

# Full comprehensive check
poetry run ruff check . --statistics
poetry run pytest tests/ -v --cov=app --cov-report=term-missing

What to Do When Checks Fail

Ruff Format Failures

If ruff format makes changes:

poetry run ruff format .
git add .  # Stage formatted files

Ruff Check Failures

Read error messages carefully:

app/api/users.py:45:5: F401 'User' imported but unused

Fix the issue:

# Remove unused import
# from models import User  ← Remove this

Pytest Failures

FAILED tests/test_users.py::test_get_user - AssertionError: ...

Debug and fix:

# Run specific test with output
poetry run pytest tests/test_users.py::test_get_user -v -s

Type Check Failures (MyPy)

app/api/users.py:45: error: Incompatible return value type

Fix type annotations:

# Before (wrong)
def get_user(id) -> User:
    return None  # Error: None is not User!

# After (correct)
def get_user(id: int) -> User | None:
    return None  # OK: None is allowed

Coverage Requirements

Maintain minimum test coverage:

• Overall coverage: 80%+
• New code coverage: 90%+
• Critical paths: 100% (auth, payments, etc.)

Check coverage:

poetry run pytest tests/ --cov=app --cov-report=term-missing

Emergency Bypass (Use Sparingly!)

In rare cases when quality gate blocks urgent fixes:

# Skip only specific check
poetry run ruff check . --ignore E501  # Ignore line length

# Or commit with --no-verify (DOCUMENT WHY!)
git commit -m "hotfix: critical bug" --no-verify

Rules for bypass:

1. Document reason in commit message
2. Create follow-up issue to fix properly
3. Never bypass tests
4. Get team approval for production

Quality Gate Success Criteria

All of these must be true:

• ✅ ruff format . makes zero changes
• ✅ ruff check . returns zero errors
• ✅ mypy app/ returns zero errors (if enabled)
• ✅ pytest tests/ all tests pass
• ✅ Test coverage ≥ 80%

Troubleshooting

"Command not found: ruff"

poetry install  # Install dependencies first

"No tests collected"

# Check test file naming
# Must be: test_*.py or *_test.py
ls tests/

"Import errors in tests"

# Set PYTHONPATH
export PYTHONPATH="${PYTHONPATH}:$(pwd)"
poetry run pytest tests/

Slow tests

# Run in parallel
poetry run pytest tests/ -n auto

# Run only fast tests
poetry run pytest tests/ -m "not slow"

Pre-commit Hook Setup (Optional)

Create .git/hooks/pre-commit:

#!/bin/bash
echo "Running quality gate..."
poetry run ruff format .
poetry run ruff check . --fix
poetry run pytest tests/ -v --maxfail=1

if [ $? -ne 0 ]; then
    echo "❌ Quality gate failed. Commit blocked."
    exit 1
fi

echo "✅ Quality gate passed!"

Make it executable:

chmod +x .git/hooks/pre-commit

Integration with CI/CD

Quality gate should also run in CI:

# .github/workflows/quality.yml
name: Quality Gate
on: [push, pull_request]
jobs:
  quality:
    runs-on: ubuntu-latest
    steps:
      - uses: actions/checkout@v3
      - run: poetry install
      - run: poetry run ruff format . --check
      - run: poetry run ruff check .
      - run: poetry run pytest tests/ --cov=app

Remember

Quality gate is not optional. It's the foundation of production-ready code.

No shortcuts. No bypasses. No "I'll fix it later."

✅ Write code → Run quality gate → Fix issues → Commit → Repeat