Default exclude-after-remap in nyc@14 loses coverage information in typescript project

[acchou]

Link to bug demonstration repository

https://github.com/acchou/nyc-bug

This is a TypeScript project that demonstrates the issue. Instructions for reproducing are in the README.md.

Expected Behavior

Coverage information should be output when exclude-after-remap is true, because "exclude" is empty ([]) and no "include" is specified.

Observed Behavior

No coverage information is reported unless exclude-after-remap is set to false.

When upgrading from nyc@13 to nyc@14, the switch to exclude-after-remap to default true causes this issue to happen by default.

Troubleshooting steps

• Changing the value of the exclude option had no effect, even if it was made empty.
• Setting exclude-after-remap to false in package.json made coverage information come back in nyc@14.

Environment Information

  System:
    OS: macOS Mojave 10.14.4
    CPU: (4) x64 Intel(R) Core(TM) i5-8210Y CPU @ 1.60GHz
    Memory: 527.37 MB / 16.00 GB
  Binaries:
    Node: 11.12.0 - ~/n/bin/node
    npm: 6.7.0 - ~/n/bin/npm
  npmPackages:
    nyc: ^14.0.0 => 14.0.0 
    typescript: 3.4.5 => 3.4.5 

I understand that exclude-after-remap has been made default true in nyc@14. Upgrading broke coverage data collection for my TypeScript project; it was previously working fine in nyc@13.

I attempted to change the value of the exclude setting but it had no effect, even setting it to empty. Only setting exclude-after-remap to false fixes the issue, and it is not obvious why that's necessary in this sort of project.

[coreyfarrell]

Can you please try adding "extension": [".ts"] to your nyc config? Setting "exclude": [] should be unnecessary (and I don't recommend using it).

[acchou]

Yes, that resolves the problem. Maybe that warrants changing the default, or some explicit documentation?

[coreyfarrell]

We're planning to add .ts to the default extension setting for nyc@15. Unfortunately this is a potentially breaking change so it cannot happen in nyc@14. You can follow #1103 for progress on this.

[JaKXz]

@acchou you can also try the configured preset for TypeScript