Drop the lock file: too much machinery for a personal CLI

Concurrent runs of the CLI can again lose an update; saves stay atomic.

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>

.gitignore

@@ -1,7 +1,6 @@
 node_modules/
 todos.json
 *.tmp
-*.lock
 .DS_Store
 
 # Personal Claude Code overrides (not shared)

src/cli.js

@@ -1,5 +1,4 @@
 #!/usr/bin/env node
-import { openSync, closeSync, statSync, rmSync } from "node:fs";
 import { load, save, add, has, complete, remove, format } from "./todo.js";
 
 const FILE = process.env.TODO_FILE ?? "todos.json";
@@ -18,29 +17,7 @@ function parseId(todos, arg) {
   return id;
 }
 
-// Hold a lock file from load to save, so two commands running at once can't lose an update.
-// A lock older than 10s is left over from a crashed run and is taken over.
-function lock(path) {
-  const lockPath = `${path}.lock`;
-  const deadline = Date.now() + 5000;
-  for (;;) {
-    try {
-      closeSync(openSync(lockPath, "wx"));
-      process.on("exit", () => rmSync(lockPath, { force: true }));
-      return;
-    } catch (err) {
-      if (err.code === "EACCES" || err.code === "EPERM") return; // read-only directory: can't lock
-      if (err.code !== "EEXIST") fail(`Could not lock ${path}: ${err.message}`);
-    }
-    const mtime = statSync(lockPath, { throwIfNoEntry: false })?.mtimeMs;
-    if (mtime !== undefined && Date.now() - mtime > 10_000) rmSync(lockPath, { force: true });
-    else if (Date.now() > deadline) fail(`${path} is busy: another todo command holds ${lockPath} (delete it if none is running)`);
-    else Atomics.wait(new Int32Array(new SharedArrayBuffer(4)), 0, 0, 25);
-  }
-}
-
 if (!["ls", "add", "done", "rm"].includes(cmd)) fail(`Unknown command: ${cmd}\n${USAGE}`);
-if (cmd !== "ls") lock(FILE);
 
 let todos;
 try {

test/cli.test.js

@@ -1,7 +1,7 @@
 import { test } from "node:test";
 import assert from "node:assert/strict";
-import { spawnSync, spawn } from "node:child_process";
+import { spawnSync } from "node:child_process";
-import { mkdtempSync, writeFileSync, readFileSync, existsSync, chmodSync, utimesSync } from "node:fs";
+import { mkdtempSync, writeFileSync, readFileSync, existsSync, chmodSync } from "node:fs";
 import { tmpdir } from "node:os";
 import { join, dirname } from "node:path";
 import { fileURLToPath } from "node:url";
@@ -49,30 +49,6 @@ test("add fails readably when no ids are left, without saving", () => {
   assert.equal(readFileSync(file, "utf8"), before);
 });
 
-test("concurrent adds don't lose updates or reuse ids", async () => {
-  const file = tempFile();
-  const runs = Array.from({ length: 12 }, (_, i) =>
-    new Promise((done) => {
-      const child = spawn(process.execPath, [CLI, "add", `t${i}`], { env: { ...process.env, TODO_FILE: file } });
-      child.on("exit", done);
-    }));
-  assert.deepEqual(await Promise.all(runs), Array(12).fill(0));
-  const todos = JSON.parse(readFileSync(file, "utf8"));
-  assert.equal(todos.length, 12);
-  assert.deepEqual(todos.map((t) => t.id).sort((a, b) => a - b), Array.from({ length: 12 }, (_, i) => i + 1));
-  assert.equal(existsSync(`${file}.lock`), false);
-});
-
-test("a stale lock from a crashed run is taken over", () => {
-  const file = tempFile();
-  writeFileSync(`${file}.lock`, "");
-  const old = new Date(Date.now() - 60_000);
-  utimesSync(`${file}.lock`, old, old);
-  const res = run(file, "add", "a");
-  assert.equal(res.status, 0, res.stderr);
-  assert.equal(existsSync(`${file}.lock`), false);
-});
-
 test("rm on a file with duplicate ids removes only the first of them", () => {
   const file = tempFile();
   writeFileSync(file, JSON.stringify([{ id: 2, text: "b", done: false }, { id: 2, text: "c", done: false }]));