Prettier After Edit

Prettier After Edit

prettier-after-edit is the behavior guide for automatic, event-driven formatting. Read this before suggesting ad-hoc format commands or manual cleanup in the same workflow.

Resolution order

Resolve Prettier for each target:

1. Search node_modules/.bin from the edited file upward through event cwd.
2. Use the first matching executable visible on PATH as a fallback.
3. Skip with an explicit message when no executable is available.

Do not call npm install, npx, Corepack, Yarn, or pnpm. The hook only uses Prettier already available to the target project or process environment.

Runtime behavior

The hook runs on PostToolUse with matcher:

apply_patch|Write|Edit|MultiEdit

It collects and deduplicates:

• tool_response.filePath
• tool_input.file_path
• tool_input.path
• tool_input.file
• every *** Add File: and *** Update File: line from string tool_input or tool_input.command

The hook canonicalizes each existing file and rejects any target resolving outside event cwd. It never expands directories or repository-wide globs.

For every supported target, it runs Prettier. It reports formatted only when file bytes change, unchanged when they do not, and distinct skipped or failed outcomes for ignore, parser, executable, or process failures.

Failure behavior

• Invalid or empty payloads produce an explicit skip message.
• Missing, non-file, and outside-cwd targets are skipped without execution.
• Missing Prettier skips only the affected target.
• A child process receives a 20-second timeout; the hook command has a 60-second timeout.
• Failure in one target does not prevent reporting other event targets.
• The hook exits 0 after reporting because the triggering edit already completed. Repository CLI and CI checks remain the enforcement boundary.

Approval boundaries

Use this automatically for selected edit events. Review and trust the current hook implementation before enabling it in a critical repository. Ask for explicit approval before bulk rewrites, repository-wide formatting, dependency installation, configuration changes, linting, or another non-idempotent expansion.