linter

name	linter
description	Run linting and formatting checks on the codebase. Use this skill when code changes are made and need static analysis validation. Runs ruff (Python) and eslint+prettier (TypeScript/React) depending on the project type. Invoke after implementation and before code review.

You are a code quality engineer. Run all relevant linters on the project and fix any issues found.

Workflow

1. Detect project type

Examine the project directory to determine the stack:

• Python (FastAPI): Look for pyproject.toml, *.py files → use ruff
• TypeScript (React): Look for package.json, eslint.config.*, *.tsx files → use eslint + prettier
• Both: Run both linters

2. Run linters

Python projects (ruff)

# Check for issues
uv run ruff check . --fix

# Format
uv run ruff format .

If ruff is not in dependencies, configure it:

1. Add ruff to dev dependencies (uv add --dev ruff or add to pyproject.toml)
2. Add a [tool.ruff] section in pyproject.toml with sensible defaults:

[tool.ruff]
target-version = "py312"
line-length = 100

[tool.ruff.lint]
select = [
    "E",      # pycodestyle errors
    "W",      # pycodestyle warnings
    "F",      # pyflakes
    "I",      # isort
    "B",      # flake8-bugbear
    "C4",     # flake8-comprehensions
    "UP",     # pyupgrade
    "ARG",    # flake8-unused-arguments
    "SIM",    # flake8-simplify
]

[tool.ruff.lint.isort]
known-first-party = ["domain", "application", "infrastructure"]

3. Run uv run ruff check . --fix and uv run ruff format .

TypeScript/React projects (eslint + prettier)

# ESLint
npx eslint . --fix

# Prettier
npx prettier --write "src/**/*.{ts,tsx}"

If the project has a lint script in package.json, prefer npm run lint or npx eslint ..

3. Report & fix

• If linters find auto-fixable issues, apply the fixes automatically
• If linters find non-auto-fixable issues, list them and fix manually
• Run the linter again after fixes to confirm zero issues
• Run the full test suite after fixing to ensure no regressions

4. Summary

Provide a table:

| Linter   | Issues found | Auto-fixed | Manual fixes | Remaining |
|----------|-------------|------------|-------------|-----------|
| ruff     | X           | Y          | Z           | 0         |
| eslint   | X           | Y          | Z           | 0         |
| prettier | X           | Y          | Z           | 0         |

Rules

• Never disable linter rules to make issues disappear — fix the underlying code
• Never add # noqa, // eslint-disable, or @ts-ignore unless the rule is genuinely a false positive, and explain why
• Run tests after every fix to catch regressions
• Only lint changed files when possible (use git diff --name-only main to scope), unless the user asks for a full lint
• Respect existing linter configs — do not modify .eslintrc, ruff.toml, pyproject.toml linter sections