Code Formatter Skill

Purpose

Automatically format and lint code across multiple languages, enforcing consistent style and fixing common issues without manual intervention.

When to Use

• •Before committing code
• •During PR preparation
• •After code generation
• •When enforcing team standards
• •Batch formatting of legacy code

Supported Languages

JavaScript/TypeScript

• •Formatter: Prettier
• •Linter: ESLint
• •Auto-fix: Import sorting, semicolons, quotes

Python

• •Formatter: Black
• •Linter: isort, autopep8
• •Auto-fix: Import sorting, line length, indentation

Go

• •Formatter: gofmt, goimports
• •Auto-fix: Import organization, formatting

Rust

• •Formatter: rustfmt
• •Auto-fix: Clippy suggestions

Other Languages

• •JSON: Prettier
• •YAML: Prettier
• •Markdown: Prettier
• •CSS/SCSS: Prettier
• •HTML: Prettier

Operations

1. Detect Language and Style

• •Auto-detect language from file extension
• •Load project-specific configuration
• •Identify style guide (Standard, Airbnb, Google, etc.)

2. Format Code

• •Apply formatter rules
• •Preserve semantics (no behavior changes)
• •Handle edge cases (strings, comments, etc.)

3. Fix Linting Issues

• •Run linter with auto-fix enabled
• •Apply safe automated fixes
• •Report remaining manual fixes needed

4. Generate Report

• •List files modified
• •Show statistics (lines changed, issues fixed)
• •Output diff for review

Scripts

main.py

# Execute formatting
python scripts/main.py format <file_or_dir> [--language=auto] [--check-only]

# Check formatting without modifying
python scripts/main.py check <file_or_dir>

# Show supported languages
python scripts/main.py languages

# Generate configuration
python scripts/main.py init --language=javascript

Language-Specific Formatters

• •format_javascript.js - ESLint + Prettier
• •format_python.py - Black + isort
• •format_go.sh - gofmt + goimports
• •format_rust.sh - rustfmt + clippy

Configuration

Project-Specific Settings

The Skill checks for configuration in this order:

1. •.prettierrc, .eslintrc (JavaScript)
2. •pyproject.toml, setup.cfg (Python)
3. •.rustfmt.toml (Rust)
4. •Memory-stored preferences
5. •Sensible defaults

Memory Integration

Stores formatting preferences:

{
  "topic": "code-formatter-preferences",
  "scope": "repository",
  "value": {
    "javascript": {
      "formatter": "prettier",
      "semi": false,
      "singleQuote": true,
      "tabWidth": 2
    },
    "python": {
      "formatter": "black",
      "lineLength": 88,
      "importSorter": "isort"
    }
  }
}

Integration Points

With PR Author/Reviewer Skill

• •Auto-format before creating PR
• •Include formatting changes in PR description
• •Validate formatting in PR checks

With Memory Hygiene Skill

• •Track formatting statistics
• •Record team preferences
• •Monitor adoption rates

With Test-First Change Skill

• •Format test files
• •Maintain consistent test style
• •Preserve test semantics

Examples

Format Single File

# Auto-detect language and format
python scripts/main.py format src/index.js

# Output:
# ✅ Formatted src/index.js (JavaScript)
# - Fixed 3 ESLint issues
# - Reformatted 127 lines

Format Directory

# Format all files in directory
python scripts/main.py format src/ --language=auto

# Output:
# ✅ Formatted 47 files
# - JavaScript: 23 files
# - TypeScript: 18 files
# - JSON: 6 files

Check Only Mode

# Check without modifying (CI/CD)
python scripts/main.py check src/

# Output:
# ❌ 3 files need formatting:
# - src/app.js
# - src/utils.js
# - src/config.json

Initialize Configuration

# Create project configuration
python scripts/main.py init --language=javascript

# Output:
# ✅ Created .prettierrc
# ✅ Created .eslintrc.json
# Configuration stored in memory

Token Economics

Without Skill (Agent formatting):

• •Parse file: 2,000 tokens
• •Analyze style: 3,000 tokens
• •Generate formatted code: 5,000 tokens
• •Explain changes: 2,000 tokens
• •Total: 12,000 tokens

With Skill (Code execution):

• •Metadata: 50 tokens
• •SKILL.md: 350 tokens
• •Script execution: 0 tokens (returns result)
• •Result parsing: 100 tokens
• •Total: 500 tokens

Savings: 95.8% (11,500 tokens saved per operation)

Success Metrics

Performance

• •Formatting time: <1 second per file
• •Batch processing: >100 files/minute
• •Memory usage: <100MB

Quality

• •Code consistency: 100%
• •Semantic preservation: 100%
• •False positives: <1%

Adoption

• •Developer usage: >90%
• •CI/CD integration: 100% of projects
• •Satisfaction rating: >4.5/5

Safety Checks

Before formatting:

1. •✅ Backup original file (in-memory)
2. •✅ Validate syntax (no broken code)
3. •✅ Preserve file permissions
4. •✅ Maintain git history

After formatting:

1. •✅ Verify file integrity
2. •✅ Check for unintended changes
3. •✅ Run syntax validation
4. •✅ Generate diff for review

Error Handling

Syntax Errors

❌ Cannot format src/broken.js: Syntax error at line 42
Recommendation: Fix syntax errors before formatting

Missing Dependencies

⚠️  Prettier not found. Install with: npm install -g prettier
Falling back to basic formatting

Configuration Conflicts

⚠️  Multiple configurations found (.prettierrc and package.json)
Using .prettierrc (higher priority)

Limitations

• •Does not fix logic errors
• •Cannot resolve complex linting issues requiring human judgment
• •May conflict with custom editor settings
• •Large files (>10,000 lines) may be slow

References

See references/ for:

• •style-guides.md - Popular style guides by language
• •configuration-examples/ - Sample configs for common setups
• •troubleshooting.md - Common issues and solutions

Code Formatter Skill v1.0.0 - Write code once, format it everywhere