Code Formatter Skill Skill

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:

.prettierrc, .eslintrc (JavaScript)
pyproject.toml, setup.cfg (Python)
.rustfmt.toml (Rust)
Memory-stored preferences
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:

✅ Backup original file (in-memory)
✅ Validate syntax (no broken code)
✅ Preserve file permissions
✅ Maintain git history

After formatting:

✅ Verify file integrity
✅ Check for unintended changes
✅ Run syntax validation
✅ 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

Agent Skills: Code Formatter Skill

Skill Files