smart-formatting — Claude Code hook: what it does, how to install
Runs formatters like Prettier, Black, gofmt, rustfmt, or php-cs-fixer automatically whenever Claude Code edits a file.
npx claude-code-templates@latest --hook development-tools/smart-formattingWhat smart-formatting does
The hook attaches to PostToolUse events for Edit and MultiEdit actions. Once Claude Code finishes modifying a file, a shell script inspects $CLAUDE_TOOL_FILE_PATH to detect the extension.
For web formats like JavaScript, TypeScript, JSON, CSS, and HTML, it invokes npx prettier --write. It runs black on Python scripts, gofmt -w on Go code, rustfmt on Rust files, and php-cs-fixer fix on PHP sources.
Each formatting command appends 2>/dev/null || true. If a required CLI tool is missing from your environment, the file simply stays unformatted without throwing errors to Claude.
What it helps with
- keep JavaScript and TypeScript files formatted with Prettier after edits
- run Black on Python modules automatically
- format Go files using gofmt right after modifications
- apply rustfmt styling to Rust code without leaving the session
Example prompts for the agent
- Refactor the authentication logic in
src/auth.ts - Add input validation to
routes/users.py - Update the data models in
internal/db.go
How to install smart-formatting
1claude-code-templates
npx claude-code-templates@latest --hook development-tools/smart-formatting2Manually: put the files in place
.claude/settings.jsonThe hooks block: event (PreToolUse, PostToolUse, Stop…) → command. Personal ones go to ~/.claude/settings.json
Step by step, with commands for each platform: Claude Code hooks: what they are, where to configure them, how to block a risky command
Questions about smart-formatting
How to install smart-formatting in Claude Code?
Run npx claude-code-templates@latest --hook development-tools/smart-formatting in your terminal or paste the hook settings into .claude/settings.json.
What tools does smart-formatting trigger?
It checks file extensions to run Prettier on web assets, Black on Python, gofmt on Go, rustfmt on Rust, and php-cs-fixer on PHP.
What happens if a formatter is not installed?
The command ignores missing tools because calls append 2>/dev/null || true. The session continues without errors, but that file remains unformatted.
Source text
smart-formatting.json · MIT
{
"description": "Smart code formatting based on file type. Automatically formats code using Prettier, Black, gofmt, rustfmt, and other language-specific formatters.",
"hooks": {
"PostToolUse": [
{
"matcher": "Edit|MultiEdit",
"hooks": [
{
"type": "command",
"command": "if [[ \"$CLAUDE_TOOL_FILE_PATH\" == *.js || \"$CLAUDE_TOOL_FILE_PATH\" == *.ts || \"$CLAUDE_TOOL_FILE_PATH\" == *.jsx || \"$CLAUDE_TOOL_FILE_PATH\" == *.tsx || \"$CLAUDE_TOOL_FILE_PATH\" == *.json || \"$CLAUDE_TOOL_FILE_PATH\" == *.css || \"$CLAUDE_TOOL_FILE_PATH\" == *.html ]]; then npx prettier --write \"$CLAUDE_TOOL_FILE_PATH\" 2>/dev/null || true; elif [[ \"$CLAUDE_TOOL_FILE_PATH\" == *.py ]]; then black \"$CLAUDE_TOOL_FILE_PATH\" 2>/dev/null || true; elif [[ \"$CLAUDE_TOOL_FILE_PATH\" == *.go ]]; then gofmt -w \"$CLAUDE_TOOL_FILE_PATH\" 2>/dev/null || true; elif [[ \"$CLAUDE_TOOL_FILE_PATH\" == *.rs ]]; then rustfmt \"$CLAUDE_TOOL_FILE_PATH\" 2>/dev/null || true; elif [[ \"$CLAUDE_TOOL_FILE_PATH\" == *.php ]]; then php-cs-fixer fix \"$CLAUDE_TOOL_FILE_PATH\" 2>/dev/null || true; fi"
}
]
}
]
}
}
© davila7 · MIT · davila7/claude-code-templates
