Weird behavior when running watch mode via yarn with async global teardown hooks

[jedwards1211]

Prerequisites

• Checked that your issue hasn't already been filed by cross-referencing issues with the faq label
• Checked next-gen ES issues and syntax problems by using the same environment and/or transpiler configuration without Mocha to ensure it isn't just a feature that actually isn't supported in the environment in question or a bug in your code.
• 'Smoke tested' the code to be tested by running it outside the real test suite to get a better sense of whether the problem is in the code under test, your usage of Mocha, or Mocha itself
• Ensured that there is no discrepancy between the locally and globally installed versions of Mocha. You can find them with: node node_modules/.bin/mocha --version(Local) and mocha --version(Global). We recommend that you not install Mocha globally.

Description

Watch mode with async global teardown hooks doesn't work properly when run via yarn. It could very well be yarn's fault, but I haven't seen weird behavior like this with any other scripts that do tricky child process spawning...

Steps to Reproduce

Repo: https://github.com/jedwards1211/yarn-mocha-watch

package.json

{
  "name": "yarn-mocha-watch",
  "version": "1.0.0",
  "main": "index.js",
  "license": "MIT",
  "scripts": {
    "test:watch": "mocha -r teardown.js test.js --watch"
  },
  "devDependencies": {
    "mocha": "^8.3.0"
  }
}

teardown.js

exports.mochaGlobalTeardown = async () => {
  await new Promise((resolve) => setTimeout(resolve, 1000))
}

test.js

describe('test setup', () => {
  it('works', () => {})
})

Expected behavior: [What you expect to happen]

When I run npm run test:watch, and then Ctrl-C, I see the following:

^C⚠ [mocha] cleaning up, please wait...
⚠ [mocha] cleaning up, please wait...
((( 1 second pause )))
npm ERR! code ELIFECYCLE
npm ERR! errno 130
...

I would expect at least a 1 second pause before exit with yarn as well, but for some reason it doesn't.

Actual behavior: [What actually happens]

When I run yarn test:watch, it exits almost immediately after I Ctrl-C, sometimes even printing ⚠ [mocha] cleaning up, please wait... after the next command prompt.

Additionally, if I press the up key after I Ctrl-C:

• If less than one second has elapsed, I get this strange error:

  node_modules/mocha/lib/runner.js:962
      throw err;
      ^
  
  Error: read EIO
      at TTY.onStreamRead (internal/stream_base_commons.js:205:27)
  Emitted 'error' event on ReadStream instance at:
      at emitErrorNT (internal/streams/destroy.js:92:8)
      at emitErrorAndCloseNT (internal/streams/destroy.js:60:3)
      at processTicksAndRejections (internal/process/task_queues.js:84:21) {
    errno: 'EIO',
    code: 'EIO',
    syscall: 'read'
  }
  

• If more than one second has elapsed, it prints ^[[A instead of the previous command (even though pressing enter will still run the previous command)

Reproduces how often: [What percentage of the time does it reproduce?]

Consistently

Versions

• The output of mocha --version and node node_modules/.bin/mocha --version: 8.3.0
• The output of node --version: 14.11.0, doesn't seem to matter
• Your operating system
  • name and version: macOS 11.2.1
  • architecture (32 or 64-bit): 64-bit
• Your shell (e.g., bash, zsh, PowerShell, cmd): bash

[jedwards1211]

Okay nevermind, this is definitely a yarn issue: yarnpkg/yarn#4667