lint-fixer

Lint Fixer Skill

Fix lint errors that automatic fixing cannot resolve. This skill provides guidance for manually resolving lint errors across different programming languages.

When to use this skill

Use this skill when:

1. Hook blocks with "LINT ERRORS REQUIRE MANUAL FIX"
2. Auto-fix ran but errors remain
3. You need to understand specific lint rules
4. Error messages reference this skill

Quick Reference by Linter

ESLint (JavaScript/TypeScript)

Common non-auto-fixable errors:

• no-undef: Variable/function not defined → Add import, declare global, or fix typo
• no-unused-vars: Variable declared but never used → Remove or use the variable
• @typescript-eslint/no-explicit-any: Avoid any type → Add proper type annotations

Documentation: https://eslint.org/docs/latest/rules/

Prettier (JavaScript/TypeScript)

Most issues auto-fix. If not:

• Check for syntax errors preventing parsing
• Ensure file is valid JS/TS

Documentation: https://prettier.io/docs/en/options.html

TypeScript

Common errors:

• Type mismatches → Ensure types align
• Missing properties → Add required properties
• Implicit any → Add explicit type annotations

Documentation: https://www.typescriptlang.org/docs/

Ruff Format (Python)

Most issues auto-fix. If not:

• Check for syntax errors preventing parsing
• Ensure file is valid Python

Documentation: https://docs.astral.sh/ruff/formatter/

Ruff (Python)

Common non-auto-fixable errors:

• F821: Undefined name → Add import or fix typo
• F841: Local variable assigned but never used → Remove or use it
• E902: Syntax error → Fix Python syntax

Documentation: https://docs.astral.sh/ruff/rules/

Black (Python)

Most issues auto-fix. If not:

• Check for syntax errors
• Ensure valid Python

Documentation: https://black.readthedocs.io/en/stable/

mypy (Python)

Common errors:

• error: Incompatible types → Fix type mismatch
• error: Missing return statement → Add return
• error: Module has no attribute → Check import

Documentation: https://mypy.readthedocs.io/en/stable/error_codes.html

SwiftLint (Swift)

Common non-auto-fixable errors:

• identifier_name: Naming convention violation → Rename to match convention
• function_body_length: Function too long → Refactor into smaller functions
• cyclomatic_complexity: Too complex → Simplify logic

Documentation: https://github.com/realm/SwiftLint/blob/main/Rules.md

SwiftFormat (Swift)

Most issues auto-fix. If not:

• Check for syntax errors
• Review .swiftformat config

Documentation: https://github.com/nicklockwood/SwiftFormat

ktlint (Kotlin)

Common non-auto-fixable errors:

• standard:max-line-length: Line too long → Break into multiple lines
• standard:function-naming: Invalid function name → Follow camelCase

Documentation: https://pinterest.github.io/ktlint/latest/rules/standard/

Detekt (Kotlin)

Common errors:

• complexity: High cyclomatic complexity → Refactor
• style: Style violations → Follow Kotlin conventions

Documentation: https://detekt.dev/docs/rules/

golangci-lint (Go)

Common errors:

• unused: Unused variable/import → Remove or use it
• errcheck: Unchecked error → Handle the error

Documentation: https://golangci-lint.run/usage/linters/

Clippy (Rust)

Common warnings:

• clippy::unwrap_used: Using unwrap → Use expect or handle Result
• clippy::todo: TODO in code → Implement or remove

Documentation: https://rust-lang.github.io/rust-clippy/master/

rustfmt (Rust)

Most issues auto-fix. If not:

• Check for syntax errors
• Review rustfmt.toml config

Documentation: https://rust-lang.github.io/rustfmt/

clang-tidy (C/C++)

Common warnings:

• modernize-*: Use modern C++ features
• readability-*: Improve code clarity
• performance-*: Optimize performance

Documentation: https://clang.llvm.org/extra/clang-tidy/

RuboCop (Ruby)

Common offenses:

• Style/*: Style guide violations → Follow Ruby style
• Lint/*: Potential bugs → Fix the issue
• Metrics/*: Complexity issues → Refactor

Documentation: https://docs.rubocop.org/rubocop/cops.html

PHP_CodeSniffer (PHP)

Common errors:

• PSR-12 violations → Follow PHP Standards Recommendations
• Naming conventions → Use PSR-4 naming

Documentation: https://github.com/squizlabs/PHP_CodeSniffer/wiki

How to Fix Lint Errors

Step 1: Identify the error

ESLint errors:
/path/to/file.js
  3:1  error  'console' is not defined  no-undef

• File: /path/to/file.js
• Line: 3
• Rule: no-undef
• Message: 'console' is not defined

Step 2: Read the file and understand context

Use the Read tool to view the code around the error line.

Step 3: Apply the fix

Based on the rule, apply the appropriate fix:

• For no-undef with console: Add browser/node environment to ESLint config
• For unused variables: Remove the variable or use it
• For type errors: Add proper type annotations

Step 4: Verify the fix

Run the linter manually:

# JavaScript
npx eslint path/to/file.js

# Python
ruff check path/to/file.py

# Swift
swiftlint lint path/to/file.swift

Suppressing Errors (Last Resort)

Only suppress when the lint rule is wrong for your use case:

// ESLint
// eslint-disable-next-line no-undef
console.log('allowed');

# Ruff/Flake8
x = unused  # noqa: F841

// SwiftLint
// swiftlint:disable:next identifier_name
let X = 1

// Detekt
@Suppress("MagicNumber")
val x = 42

Best Practices

1. Fix root cause - Don't just suppress errors
2. Check project config - Rules may be customized
3. Run tests after fixing - Ensure no regressions
4. Document suppressions - Explain why rule is disabled