nyc 15 gives no coverage without the useSpawnWrap option

[adjerbetian]

Link to bug demonstration repository

https://github.com/adjerbetian/nyc-bug-demo-use-spawn

Expected Behavior

I would want to have the coverage, but I get nothing in the output

I tried to debug, and when I use the flag --use-spawn-wrap I get the expected result:

📝 This problem does not occur on nyc@14.

Observed Behavior

Troubleshooting steps

• run npx nyc mocha --> ❌ no coverage
• run npx nyc --use-spawn-wrap mocha --> ✔️ coverage
• still occurring when I put cache: false in my nyc config

Environment Information

  System:
    OS: Linux 4.15 Ubuntu 18.04.4 LTS (Bionic Beaver)
    CPU: (12) x64 Intel(R) Core(TM) i9-8950HK CPU @ 2.90GHz
    Memory: 10.25 GB / 31.07 GB
  Binaries:
    Node: 12.16.1 - /usr/bin/node
    npm: 6.14.4 - /usr/bin/npm
  npmPackages:
    nyc: ^15.0.1 => 15.0.1 

[coreyfarrell]

I am not able to reproduce this issue, npx nyc mocha in your repository works correctly on Fedora 30 and Ubuntu 18.04.4.

Fedora 30 is what I run locally, I tested with node 12.16.2 installed by nvm. I tested ubuntu under docker using the ubuntu:18.04 image and again installing node.js using nvm.

This is an important issue for us to figure out as --use-spawn-wrap is an option that was added "just in case", the intent is to eventually remove it from a future semver-major.

Your environment info lists node 12.16.1 as being installed to /usr/bin/node. How did you install this? apt-get install nodejs gave me 8.10.0 and nvm doesn't install to /usr/bin.

[adjerbetian]

@coreyfarrell Thank you for answering.

My ubuntu just updated the node version to 12.16.2 and the problem is gone. I tried to look at the changelog to see what it could be but it's too big.

I suppose we can close here, unless you want to keep digging.

[coreyfarrell]

Thanks for the update. This is odd as I'm not seeing the issue using 12.16.1 on Fedora either. Without being able to reproduce I think we can close this issue, if you do ever see it again please be sure to post a new issue!

[danielSONCCO]

@coreyfarrell do you reproduce if you employ ?

• node 12.13.0 (edit: installed with npm)
• nyc 15.0.1

bug looks coming of the usage of node-preload https://github.com/istanbuljs/nyc/blob/master/bin/nyc.js#L62
https://github.com/cfware/node-preload#limitations
Those limitations can explain that the result isn't deterministic

On my pc, without the useSpawnWrap option, lib/wrap.js is not executed by that preload
This causes that onExit isn't called, then writeCoverageFile isn't called

wdyt of replacing node-preload by something else ?

[coreyfarrell]

Worker threads are not supported by spawn-wrap at all. node-preload is the replacement, if it is failing in a case where spawn-wrap worked I need to see a reproducible demo suit can be fixed. Be aware spawn-wrap fails in many situations, especially on Windows.