Error when merging Jest coverage using nyc

🐛 Bug Report

I’m using nrwl’s nx with angular, jest and cypress. For unit test code coverage reports I execute npm run test -- --code-coverage and the report looks good when opening. Now I’d like to use nyc to merge this report with the one generated from cypress. Running nyc merge runs fine on the cypress coverage json, but on Jest’s I get Invalid file coverage object, missing keys, found:data When I look in the coverage-final.json file from Jest, I do see html objects containing data properties, while the .ts objects have keys properties. The cypress coverage-final.json output has html objects containing keys properties, which leads me to believe the problem is with the way Jest outputs coverage under certain circumstances. Possibly it’s an Istanbul issue, but I’m posting it here as it seems Istanbul’s nyc, that uses the same version of Istanbul as Jest is not able to process the coverage files.

Also worth mentioning, with Jest 24 the coverage-final.json didn’t contain data properties in html entries.

To Reproduce

Not able to reproduce using a minimal setup.

Expected behavior

No data properties to be present on file objects in coverage-final.json.

Link to repl or repo (highly encouraged)

I created a small setup but there the data properties on the .html files somehow were not present. So at the moment I am unable to reproduce outside of the environment this is happening.

envinfo

  System:
    OS: Windows 10 10.0.18363
    CPU: (8) x64 Intel(R) Core(TM) i7-7700 CPU @ 3.60GHz
  Binaries:
    Node: 13.6.0 - C:\Program Files\nodejs\node.EXE
    Yarn: 1.22.0 - C:\Program Files\nodejs\yarn.CMD
    npm: 6.13.4 - C:\Program Files\nodejs\npm.CMD
  npmPackages:
    jest: 25.2.4 => 25.2.4

[zauni]

@postmodernistx thanks, with your comment I got it fixed! In my case HTML files were the troublemakers and I could fix it by adding this to jest.config.js:

coveragePathIgnorePatterns: ['/node_modules/', 'src/(?=.*\\.html$)']

[postmodernistx]

If it might help anyone, here’s what I ended up doing (probably not a great solution, though 😅 ):

The code coverage report generated by Jest, when utilizing vue-cli-service test:unit added the data key to all files that were (in my case) .png, .stories.js and .(spec|test).(js|ts).

In my jest.config.js I could remove some of those troublemakers by adding the coveragePathIgnorePatterns property:

coveragePathIgnorePatterns: [
  '<rootDir>/src/assets/*',
  '<rootDir>/src/stories/*',
],

But this didn’t cover all cases, so I ended up writing a tiny script that stripped the coverage-final.json file of the remaining items with the data property. Some mad regex skills could probably have covered those cases in the coveragePathIgnorePatterns array.

Screenshot example below (coverage-final.json), png files have the data property but regular vue components don’t: