posttooluse_writeedit.py

#!/usr/bin/env python3
"""PostToolUse hook for Write | Edit — formatter dispatch.

After a successful Write or Edit, format the touched file in place:

  - `.py`                         -> `uv run ruff check --fix` + `uv run ruff format`
  - `.ts .tsx .js .jsx .json`     -> `npx --no-install prettier -w` (from frontend/)
  - `.css .html .md`              -> `npx --no-install prettier -w` (from frontend/)

Silent on failure — the write already landed; formatting is best-effort. Exit code
is always 0 so Claude Code never rolls back the edit over a missing formatter.
"""

from __future__ import annotations

import contextlib
import json
import os
import subprocess
import sys
from pathlib import Path

PY_EXTENSIONS = {".py"}
PRETTIER_EXTENSIONS = {
    ".ts",
    ".tsx",
    ".js",
    ".jsx",
    ".json",
    ".css",
    ".html",
    ".md",
}


def project_dir() -> Path:
    env = os.environ.get("CLAUDE_PROJECT_DIR")
    if env:
        return Path(env)
    return Path(__file__).resolve().parent.parent.parent


def run_quiet(cmd: list[str], cwd: Path) -> None:
    with contextlib.suppress(FileNotFoundError, subprocess.TimeoutExpired):
        subprocess.run(
            cmd,
            cwd=cwd,
            stdout=subprocess.DEVNULL,
            stderr=subprocess.DEVNULL,
            check=False,
            timeout=60,
        )


def format_python(path: Path, base: Path) -> None:
    run_quiet(["uv", "run", "ruff", "check", "--fix", str(path)], cwd=base)
    run_quiet(["uv", "run", "ruff", "format", str(path)], cwd=base)


def format_prettier(path: Path, base: Path) -> None:
    frontend = base / "frontend"
    if not frontend.is_dir():
        return
    # --no-install so a checkout without prettier installed silently no-ops
    # instead of triggering an npx download.
    run_quiet(
        ["npx", "--no-install", "prettier", "-w", str(path)],
        cwd=frontend,
    )


def main() -> None:
    try:
        payload = json.load(sys.stdin)
    except json.JSONDecodeError:
        return
    if not isinstance(payload, dict):
        return
    tool_input = payload.get("tool_input")
    if not isinstance(tool_input, dict):
        return
    file_path = tool_input.get("file_path", "")
    if not isinstance(file_path, str) or not file_path:
        return

    path = Path(file_path)
    if not path.is_absolute():
        path = project_dir() / path
    if not path.exists():
        return

    suffix = path.suffix.lower()
    base = project_dir()

    if suffix in PY_EXTENSIONS:
        format_python(path, base)
    elif suffix in PRETTIER_EXTENSIONS:
        format_prettier(path, base)


if __name__ == "__main__":
    main()