code-formatter

What this skill does

# 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

| Error | Cause | Solution |
|---|---|---|
| `prettier: command not found` | Prettier not installed globally or locally | Run `npm install -g prettier` or `npx prettier --version` to use npx |
| Syntax errors in source files | Malformed code that Prettier cannot parse | Fix syntax errors first using `npx eslint --fix-dry-run <file>` then retry formatting |
| Configuration conflicts | Multiple `.prettierrc` files or conflicting `editorconfig` | Locate all config files with `find . -name ".prettier*"` and consolidate to a single config |
| Permission denied on write | File or directory lacks write permission | Run `chmod u+w <file>` to grant write access |
| Parser not found for file type | Unsupported file extension or missing Prettier plugin | Install the appropriate Prettier plugin (e.g., `prettier-plugin-svelte`) or exclude the file type |

## 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](https://prettier.io/docs/en/) -- official configuration and CLI reference
- [ESLint](https://eslint.org/) -- complementary linting and code quality tool
- [Husky](https://typicode.github.io/husky/) -- git hooks for pre-commit formatting enforcement