Function createProjectWatcher

packages/cli/src/server/fileWatcher.ts:32–76

(projectDir: string)

}

export function createProjectWatcher(projectDir: string): ProjectWatcher {
  const listeners = new Set<FileChangeListener>();
  let debounceTimer: ReturnType<typeof setTimeout> | null = null;
  let watcher: FSWatcher | null = null;

  try {
    watcher = watch(projectDir, { recursive: true }, (_event, filename) => {
      if (!filename) return;
      const relativePath = filename.toString();
      if (!shouldWatchProjectFile(relativePath)) return;

      if (debounceTimer) clearTimeout(debounceTimer);
      debounceTimer = setTimeout(() => {
        for (const fn of listeners) {
          fn(relativePath);
        }
      }, DEBOUNCE_MS);
    });
    // fs.watch can fail asynchronously too (e.g. EMFILE from exhausted OS watch
    // handles) — that surfaces as an 'error' event, not a thrown exception. An
    // EventEmitter 'error' with no listener crashes the whole process, so this
    // listener is required for the same "degrade gracefully" the catch below
    // already promises for the synchronous failure mode.
    watcher.on("error", () => {
      watcher?.close();
      watcher = null;
    });
  } catch {
    // fs.watch may fail on some platforms — degrade gracefully (no auto-refresh)
  }

  return {
    addListener(fn) {
      listeners.add(fn);
    },
    removeListener(fn) {
      listeners.delete(fn);
    },
    close() {
      if (debounceTimer) clearTimeout(debounceTimer);
      watcher?.close();
      listeners.clear();
    },
  };
}