Invalid code coverage with react-native/jest/preprocessor.js

[retyui]

• Review the documentation: https://facebook.github.io/react-native
• Search for existing issues: https://github.com/facebook/react-native/issues
• Use the latest React Native release: https://github.com/facebook/react-native/releases

Environment

  React Native Environment Info:
    System:
      OS: Linux 4.15 Linux Mint 18.3 (Sylvia)
      CPU: x64 Intel(R) Core(TM) i5-8250U CPU @ 1.60GHz
      Memory: 1.10 GB / 7.67 GB
      Shell: 2.7.1 - /usr/bin/fish
    Binaries:
      Node: 8.11.3 - /usr/bin/node
      Yarn: 1.7.0 - /usr/bin/yarn
      npm: 6.2.0 - /usr/bin/npm
    SDKs:
      Android SDK:
        Build Tools: 23.0.1, 26.0.3, 27.0.3, 28.0.1
        API Levels: 23, 25, 26, 28
    npmPackages:
      react: 16.4.1 => 16.4.1 
      react-native: ^0.56.0 => 0.56.0 
    npmGlobalPackages:
      react-native-cli: 2.0.1

Description

We use js Generators in own project, and when we run test jest --coverage we have a bad result because of the react-native/jest/preprocessor.js polyfilled function*(){} and create some helper function that affect to coverage result

Reproducible Demo

Info: https://gist.github.com/retyui/760ff91c0fab7310f8cea8c7e5c43978
Result:

[stale]

Hey there, it looks like there has been no activity on this issue recently. Has the issue been fixed, or does it still require the community's attention? This issue may be closed if no further activity occurs. You may also label this issue as "For Discussion" or "Good first issue" and I will leave it open. Thank you for your contributions.

[Traviskn]

@retyui Did you find a solution to this? I am also having issues with code coverage reports after upgrading to react-native 0.57

[retyui]

@Traviskn I didn't find a solution to this problem

[vidit-bhatia]

@retyui I think we must open this issue again. This does not make sense I see exact same thing and this does not mkae sense my team has a mandate for 80% code coverage per component and I do not think anyone can achieve it with this bug

[cpojer]

I recognize this issue exists but it's unlikely anyone will spend time on fixing this. I'll close this issue but if you need this fixed I recommend investigating and sending a PR with a fix :)

[alexcanessa]

I'm just using babel-jest as a transform, instead of using the preprocessor and it worked.
Not sure yet if it's going to have bad consequences 😂