Pressing `Ctrl+C` when `--inspector-brk` is used but debugger is not connected hangs Vitest

[sheremet-va]

Describe the bug

When trying to debug Vitest with a break, Vitest hangs indefinitely if no connection is ever established.

Reproduction

vitest --inspect-brk --no-file-parallelism
Ctrl+C

https://stackblitz.com/fork/github/vitest-dev/vitest/tree/main/examples/basic?initialPath=__vitest__/

System Info

Any

Used Package Manager

npm

Validations

• Follow our Code of Conduct
• Read the Contributing Guidelines.
• Read the docs.
• Check that there isn't already an issue that reports the same bug to avoid creating a duplicate.
• Check that this is a concrete bug. For Q&A open a GitHub Discussion or join our Discord Chat Server.
• The provided reproduction is a minimal reproducible example of the bug.

[AriPerkkio]

This is what's happening when CTRL+c is pressed:

import { isMainThread, Worker } from "node:worker_threads";
import { fileURLToPath } from "node:url";
import inspector from "node:inspector";

const filename = fileURLToPath(import.meta.url);

if (isMainThread) {
  const worker = new Worker(filename);
  await new Promise((r) => setTimeout(r, 1_000));

  console.log("Terminating...");
  const timeout = setTimeout(() => console.log("Stuck here"), 2_000);
  await worker.terminate();

  clearTimeout(timeout);
  console.log("Done");
} else {
  inspector.open();
  inspector.waitForDebugger();
}

$ node worker.mjs 
Debugger listening on ws://127.0.0.1:9229/65cec5ee-87d3-4a0c-b481-ac9d257a96f5
For help, see: https://nodejs.org/en/docs/inspector
Terminating...
Stuck here

The ctx.close() is stuck here:

vitest/packages/vitest/src/node/pools/threads.ts

Line 212 in 672a1ed

close: () => pool.destroy(),

[sheremet-va]

Maybe we can send the event Runtime.runIfWaitingForDebugger somehow before terminating 🤔

[AriPerkkio]

For that I think we would need to connect to the Worker's inspector session from main thread with web socket. There's also session.connectToMainThread() but I've never got it working and there are no examples for it anywhere.

For the inspector session's web socket connection we have similar setups here:

vitest/test/inspect/test/inspect.test.ts

Lines 13 to 16 in 6157282

	await vitest.waitForStderr('Debugger listening on ')
	const url = vitest.stderr.split('\n')[0].replace('Debugger listening on ', '')
	const { receive, send } = await createChannel(url)

Worker not terminating when it's paused in waitForDebugger() sounds like a Node bug to me. Though it's still somehow able to terminate when default CTRL+c happens and process.stdin raw mode is not overwritten. 🤔

[sheremet-va]

For that I think we would need to connect to the Worker's inspector session from main thread with web socket.

Can't we send postMessage from the main thread to the worker where the inspector is already initiated? If setTimeout is not blocked, I assume it also will not be blocked

[AriPerkkio]

Inside the Worker setTimeout should be blocked when waitForDebugger() is active. I don't think Worker receives anything from parentPort.postMessage either.

But connecting to the inspector session and sending Runtime.runIfWaitingForDebugger like done here should work:

vitest/test/inspect/test/inspect.test.ts

Lines 22 to 25 in 6157282

	const paused = receive('Debugger.paused')
	send({ method: 'Runtime.runIfWaitingForDebugger' })
	const { params } = await paused

[AriPerkkio]

This would work:

import { isMainThread, parentPort, Worker } from "node:worker_threads";
import { fileURLToPath } from "node:url";
import inspector from "node:inspector";
import WebSocket from "ws";

const filename = fileURLToPath(import.meta.url);

if (isMainThread) {
  const worker = new Worker(filename);
  const url = await new Promise((resolve) => worker.on("message", resolve));

  const timeout = setTimeout(async () => {
    console.log("Timeout");

    const ws = new WebSocket(url);
    await new Promise((resolve) => ws.on("open", resolve));

    ws.send(JSON.stringify({ method: "Runtime.runIfWaitingForDebugger", id: 2 }));
    ws.close();
  }, 2_000).unref();

  await worker.terminate();
  clearTimeout(timeout);
  console.log("Done");
} else {
  inspector.open();
  parentPort.postMessage(inspector.url());
  inspector.waitForDebugger();

  console.log("Running"); // Never logged
}

[AriPerkkio]

This should be fixed in Node v22.2.0: nodejs/node#52971

$ node -v
v22.2.0

$ node worker-repro.mjs 
Debugger listening on ws://127.0.0.1:9229/2b239484-37a6-4a4d-ba9d-099db758906d
For help, see: https://nodejs.org/en/docs/inspector
Terminating...
Done