Lint and Validate Skill

MANDATORY: Run appropriate validation tools after EVERY code change. Do not finish a task until the code is error-free.

For the full pipeline (build → lint → type-check → tests → coverage), use mk:verify. mk:lint-and-validate is a lint-only subset intended for post-edit quick checks.

Procedures by Ecosystem

See references/linter-commands.md for full command reference per ecosystem (Node.js/TS, Python) and Shared validation scripts.

The Quality Loop

1. Write/Edit Code
2. Run Audit: npm run lint && npx tsc --noEmit
3. Analyze Report: Check the "FINAL AUDIT REPORT" section.
4. Fix & Repeat: Submitting code with "FINAL AUDIT" failures is NOT allowed.

Error Handling

• If lint fails: Fix the style or syntax issues immediately.
• If tsc fails: Correct type mismatches before proceeding.
• If no tool is configured: Check the project root for .eslintrc, tsconfig.json, pyproject.toml and suggest creating one.

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Strict Rule: No code should be committed or reported as "done" without passing these checks.

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Scripts

See references/linter-commands.md for full command tables and Shared validation scripts.

Gotchas

• ESLint flat config (eslint.config.mjs) and legacy .eslintrc are mutually exclusive — ESLint 9 auto-detects the flat config format and ignores any .eslintrc.* files in the same directory; if the project has both, the flat config silently wins and all legacy extends rules are dropped without error, making it look like rules pass when they were never loaded.
• eslint --fix run on unstaged files destroys uncommitted work — --fix writes changes directly to disk without prompting; if run on a file with uncommitted edits, ESLint's changes overwrite the working tree diff; always stage changes with git add -p before running --fix, or use --fix-dry-run to preview.
• TypeScript ESLint parser version must match the installed typescript version — @typescript-eslint/parser pins against specific TypeScript minor versions; a TypeScript upgrade (e.g., 5.3 → 5.5) without bumping @typescript-eslint/parser causes Unexpected token parse errors on new syntax even though tsc accepts it fine.
• extends order determines rule precedence and later entries win — in legacy .eslintrc, extends: ['plugin:vue/recommended', 'prettier'] works (prettier overrides vue formatting), but reversing to ['prettier', 'plugin:vue/recommended'] re-enables vue formatting rules that conflict with prettier, producing unfixable lint errors on every save.
• Prettier and ESLint format rules conflict when both run on the same file — eslint --fix applying quotes: 'single' then prettier reformatting to double quotes creates an infinite fix loop in editor save hooks; disable all formatting rules in ESLint (eslint-config-prettier) and let Prettier own formatting exclusively.