PR Reviewer / Linter Enforcer

When to use this skill

• User asks to lint or format code
• User wants to review code quality before a PR
• User mentions ESLint, Prettier, or stylelint
• User asks to fix formatting or style issues
• User wants to check changed files for violations
• User mentions code consistency or style enforcement

Workflow

• Identify changed files (staged or branch diff)
• Detect available linting tools in project
• Run linters against changed files only
• Collect and categorize issues
• Present issues with fix suggestions
• Apply automatic fixes if requested
• Verify fixes resolved issues

Instructions

Step 1: Identify Changed Files

For staged changes:

git diff --cached --name-only --diff-filter=ACMR

For branch comparison:

git diff --name-only origin/main...HEAD

Filter to lintable files:

git diff --cached --name-only --diff-filter=ACMR | grep -E '\.(js|jsx|ts|tsx|vue|css|scss|json|md)$'

Step 2: Detect Available Linters

Check for linter configurations in project root:

Tool	Config Files
ESLint	.eslintrc.*, eslint.config.*, package.json
Prettier	.prettierrc.*, prettier.config.*, package.json
stylelint	.stylelintrc.*, stylelint.config.*, package.json

Verify tools are installed:

npm ls eslint prettier stylelint 2>/dev/null || yarn list --pattern "eslint|prettier|stylelint" 2>/dev/null

Step 3: Run Linters on Changed Files

ESLint (JavaScript/TypeScript):

npx eslint --format stylish <files>

With auto-fix preview:

npx eslint --fix-dry-run --format json <files>

Prettier (formatting):

npx prettier --check <files>

Show what would change:

npx prettier --write --list-different <files>

stylelint (CSS/SCSS):

npx stylelint <css-files>

Step 4: Categorize Issues

Group issues by severity and type:

Errors (must fix):

• Syntax errors
• Type errors
• Security vulnerabilities
• Unused variables in critical paths

Warnings (should fix):

• Unused imports
• Missing accessibility attributes
• Deprecated API usage

Style (nice to fix):

• Formatting inconsistencies
• Naming conventions
• Import ordering

Step 5: Present Issues

Format findings clearly:

## Linting Report

### Errors (3)

| File         | Line | Rule                               | Message                              |
| ------------ | ---- | ---------------------------------- | ------------------------------------ |
| src/utils.ts | 42   | @typescript-eslint/no-explicit-any | Unexpected any                       |
| src/api.ts   | 15   | no-unused-vars                     | 'response' is defined but never used |
| src/index.ts | 8    | import/no-unresolved               | Unable to resolve path               |

### Warnings (2)

| File           | Line | Rule                                     | Message                   |
| -------------- | ---- | ---------------------------------------- | ------------------------- |
| src/Button.tsx | 23   | jsx-a11y/click-events-have-key-events    | Missing keyboard handler  |
| src/utils.ts   | 67   | @typescript-eslint/no-non-null-assertion | Avoid non-null assertions |

### Formatting (5 files)

- src/components/Card.tsx
- src/hooks/useAuth.ts
- src/pages/Home.tsx
- src/styles/main.css
- src/types/index.ts

Step 6: Apply Fixes

Auto-fix all fixable issues:

npx eslint --fix <files>
npx prettier --write <files>
npx stylelint --fix <css-files>

Fix specific rule categories:

# Only formatting fixes
npx eslint --fix --rule 'indent: error' --rule 'semi: error' <files>

# Only import sorting
npx eslint --fix --rule 'import/order: error' <files>

Step 7: Verify Fixes

Re-run linters to confirm resolution:

npx eslint <files> && npx prettier --check <files> && echo "✓ All checks passed"

Configuration Detection

ESLint Config Patterns

Check for flat config (ESLint 9+):

ls eslint.config.{js,mjs,cjs} 2>/dev/null

Check for legacy config:

ls .eslintrc.{js,cjs,json,yml,yaml} 2>/dev/null

Prettier Config Patterns

ls .prettierrc{,.json,.yml,.yaml,.js,.cjs,.mjs} prettier.config.{js,cjs,mjs} 2>/dev/null

Package.json Scripts

Check for existing lint scripts:

npm pkg get scripts.lint scripts.format scripts.style 2>/dev/null

Prefer using project scripts when available:

npm run lint -- --fix
npm run format

Common Fix Patterns

Unused Imports

// Before
import { useState, useEffect, useCallback } from "react";
// Only useState used

// After
import { useState } from "react";

Missing Accessibility

// Before
<div onClick={handleClick}>Click me</div>

// After
<button type="button" onClick={handleClick}>Click me</button>

Formatting Issues

// Before
const obj = { foo: "bar", baz: 42 };

// After
const obj = { foo: "bar", baz: 42 };

Integration with Git Hooks

If user wants pre-commit enforcement, suggest:

npx husky add .husky/pre-commit "npx lint-staged"

With lint-staged config in package.json:

{
  "lint-staged": {
    "*.{js,jsx,ts,tsx}": ["eslint --fix", "prettier --write"],
    "*.{css,scss}": ["stylelint --fix", "prettier --write"],
    "*.{json,md}": ["prettier --write"]
  }
}

Validation

Before completing:

• All errors are resolved or acknowledged
• Warnings reviewed and addressed where appropriate
• Formatting is consistent
• No new issues introduced by fixes
• Changes staged for commit

Error Handling

• Linter not installed: Run npm install --save-dev <tool> or check if project uses yarn/pnpm.
• No config found: Linter may use defaults. Run npx <tool> --init to create config.
• Command fails: Run npx <tool> --help for available options.
• No changed files: Run git status to verify. May need to stage changes first.

Resources

• ESLint Documentation
• Prettier Documentation
• stylelint Documentation
• lint-staged