Mocha 8: Failing async test exits mocha watch mode on reload

[mantoni]

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.
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• 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

mocha --watch exists on second run if async test fails.

Steps to Reproduce

With this test:

describe('mocha watch issue', () => {

  it('async', (done) => {
    setTimeout(() => {
      throw new Error('Fail');
    }, 1);
  });

});

Running:

mocha --watch

And then touching the test file to trigger a second run of the test.

Expected behavior: [What you expect to happen]

The test fails on the second run exactly like on the first run and mocha keeps watching.

Actual behavior: [What actually happens]

Mocha exits on the second test run.

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

100%

Versions

• The output of mocha --version and node node_modules/.bin/mocha --version: 8.0.1
• The output of node --version: v14.4.0
• Your operating system
  • name and version: macOS Catalina 10.15.5
  • architecture (32 or 64-bit): 64
• Your shell (e.g., bash, zsh, PowerShell, cmd): fish
• Your browser and version (if running browser tests): –
• Any third-party Mocha-related modules (and their versions): –
• Any code transpiler (e.g., TypeScript, CoffeeScript, Babel) being used (and its version): –

Additional Information

I have reported the very same issue for mocha 7 in #4143 and it got fixed. Maybe it's the same issue that somehow found its way back 😄

[boneskull]

Yes, we've been monkeying with that code path, trying to reduce the chance we leak uncaughtException listeners.

[boneskull]

cc @juergba who may have interest in this one. @mantoni if it's blocking you, adding a test to reproduce this in a PR would be helpful to get us moving. test/integration/options/watch.spec.js seems reasonable, and add a fixture in test/integration/fixtures/options/watch/

[boneskull]

I think this is closed by #4382. Please let me know if it isn't.