No coverage when running with mocha --parallel mode

[curbengh]

Link to bug demonstration repository

hexojs/hexo#4374

Expected Behavior

nyc --reporter=lcovonly mocha --parallel should produce "./coverage/lcov.info".
nyc --reporter=text-summary mocha --parallel should display coverage report.

Observed Behavior

nyc --reporter=lcovonly mocha --parallel generates an empty "./coverage/lcov.info".
nyc --reporter=text-summary mocha --parallel:

=============================== Coverage summary ===============================
Statements   : Unknown% ( 0/0 )
Branches     : Unknown% ( 0/0 )
Functions    : Unknown% ( 0/0 )
Lines        : Unknown% ( 0/0 )
================================================================================

Troubleshooting steps

No issue in mocha's default serial mode.

Environment Information

  System:
    OS: Linux 4.9 Solus 4.1
    CPU: (1) x64 Intel(R) Core(TM) i7-4500U CPU @ 1.80GHz
    Memory: 1.53 GB / 2.94 GB
  npmPackages:
    nyc: ^15.0.0 => 15.1.0 

".mocharc.yml"

color: true
reporter: spec
ui: bdd
full-trace: true
exit: true
require: 
  - "chai/register-should"
parallel: true

[coreyfarrell]

If things work without using --parallel could you cross-post an issue to the mochajs repository so they are aware of this potential issue? I haven't had a chance to look into the mocha --parallel implementation so I'm not sure where the issue comes from. Please be sure to link that issue to this one.

I'm pretty busy currently so it might be a while before I have a chance to investigate, for now you will probably have to disable parallel for coverage testing.

[stale]

Is this still relevant? If so, what is blocking it? Is there anything you can do to help move it forward?

This issue has been automatically marked as stale because it has not had recent activity. It will be closed if no further activity occurs.