Imported from gabrielmoreira/agent-skills-mirror (mirrors/repos/jeremylongshore@tons-of-skills-marketplace/plugins/examples/formatter/skills/code-formatter/SKILL.md). Install upstream with npx skills add gabrielmoreira/agent-skills-mirror --skill code-formatter. Copyright stays with the author (MIT).

Code Formatter

Overview

Formats and validates code files using Prettier and related formatting tools. Supports JavaScript, TypeScript, JSON, CSS, Markdown, and many other file types.

Prerequisites

• Node.js (v16+) and npm/npx installed
• Prettier available globally (npm install -g prettier) or locally in the project
• Write permissions for target files and configuration directories
• Supported file types present in the project (.js, .jsx, .ts, .tsx, .json, .css, .md)

Instructions

1. Check whether Prettier is available by running npx prettier --version. If missing, install it locally with npm install --save-dev prettier or globally with npm install -g prettier.
2. Detect existing configuration by searching for .prettierrc, .prettierrc.json, prettier.config.js, or a "prettier" key in package.json. If no configuration exists, create a .prettierrc with sensible defaults (see ${CLAUDE_SKILL_DIR}/references/implementation.md).
3. Run npx prettier --check "**/*.{js,jsx,ts,tsx,json,css,md}" --ignore-path .prettierignore to identify files that need formatting. Report the count and list of non-conforming files.
4. Apply formatting to identified files using npx prettier --write on the target paths. For single files, specify the exact path; for directories, use glob patterns.
5. Create or update .prettierignore to exclude generated outputs (dist/, build/, *.min.js, *.min.css), dependencies (node_modules/, vendor/), and lock files.
6. Optionally set up pre-commit enforcement by installing husky and lint-staged, then configuring lint-staged in package.json to run prettier --write on staged files matching supported extensions.
7. Run a final npx prettier --check to confirm all target files now conform to the configured style rules.

Output

A formatting execution report containing:

• Count of files checked and files reformatted
• List of files that were modified with before/after formatting status
• Configuration file(s) created or updated (.prettierrc, .prettierignore)
• Any git hook integration changes applied
• Confirmation of final formatting compliance

Error Handling

Examples

Format a single file: Trigger: "Format src/app.js" Process: Run npx prettier --write src/app.js. Report the file as reformatted or already conformant.

Project-wide formatting setup: Trigger: "Set up code formatting for this project." Process: Create .prettierrc with project defaults, create .prettierignore excluding build outputs, run npx prettier --write "src/**/*.{js,ts,json,css}", install husky and lint-staged for pre-commit hooks, verify compliance.

Check formatting without modifying files: Trigger: "Check formatting across the project." Process: Run npx prettier --check "**/*.{js,jsx,ts,tsx,json,css,md}". Report non-conforming files with their paths. Suggest npx prettier --write to fix.

Resources

• ${CLAUDE_SKILL_DIR}/references/implementation.md -- detailed implementation guide with configuration examples
• ${CLAUDE_SKILL_DIR}/references/errors.md -- common error scenarios and solutions
• Prettier documentation -- official configuration and CLI reference
• ESLint -- complementary linting and code quality tool
• Husky -- git hooks for pre-commit formatting enforcement