Add combined coverage threshold for directories

[ttmarek]

Summary

Right now you can specify a global threshold in Jest and a threshold for files that match a glob pattern. But you can't specify a threshold for a given directory. This pull request adds that functionality without taking away any functionality from before. With this pull request there will be three possible ways to set a coverage threshold:

1. global applies the threshold to every covered file.
2. path applies the threshold to a path (either a directory or a file).
3. glob applies the threshold to any file matching a glob pattern.

For example, before you could do:

{
  "coverageThreshold": {
    "global": {
      "branches": 50,
      "functions": 50,
      "lines": 50,
      "statements": 50
    },
    "./src/components/**/*.js": {
      "branches": 40,
      "statements": 40
    },
    "./src/api/very-important-module.js": {
      "branches": 100,
      "functions": 100,
      "lines": 100,
      "statements": 100
    }
  }
}

And this would apply a threshold separately...

• to every file matching the "./src/components/**/*.js" glob pattern
• to the "./src/api/very-important-module.js" file
• and any remaining covered files (under the global threshold).

But what if you want to set a threshold for the entire components directory? That is, what if you don't care about the threshold of each individual .js file in the components directory, but you do want to set a combined coverage threshold for all your components. Something like:

{
  "coverageThreshold": {
    "global": {
      "branches": 50,
      "functions": 50,
      "lines": 50,
      "statements": 50
    },
    "./src/components/": {
      "branches": 40,
      "statements": 40
    },
    "./src/reducers/**/*.js": {
      "statements": 90,
    },
    "./src/api/very-important-module.js": {
      "branches": 100,
      "functions": 100,
      "lines": 100,
      "statements": 100
    }
  }
}

And this would apply a threshold separately...

• to the entire"./src/components" directory (combined coverage for each file under the directory).
• to every file matching the "./src/reducers/**/*.js" glob pattern.
• to the "./src/api/very-important-module.js" file
• and any remaining covered files (under the global threshold).

Test plan

I added a few unit tests that tests this new functionality. I left every other test in the test suite alone to demonstrate that there are no regressions in functionality. Let me know if you think we need to add some more tests, or if there are some integration test that I can create/update.

[codecov-io]

Codecov Report

Merging #4885 into master will increase coverage by 0.19%.
The diff coverage is 100%.

@@            Coverage Diff             @@
##           master    #4885      +/-   ##
==========================================
+ Coverage   59.75%   59.95%   +0.19%     
==========================================
  Files         195      195              
  Lines        6533     6562      +29     
  Branches        4        4              
==========================================
+ Hits         3904     3934      +30     
+ Misses       2629     2628       -1

Impacted Files	Coverage Δ
...ckages/jest-cli/src/reporters/coverage_reporter.js	66.4% <100%> (+10.85%)	⬆️

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[SimenB]

Looking good! Can you update the docs and changelog as well?

[ttmarek]

Thanks for the review @SimenB.

I've updated the changelog and docs. Let me know if you spot any areas that could be improved.

[SimenB]

LGTM, but this is a part of the code base I haven't touched, so should have another set of eyes

[Ben07]

"coverageThreshold": {
    "src/app/Market/components/Cloud/Item.js": {
      "branches": 80,
      "functions": 80,
      "lines": 80,
      "statements": 80
    }
  },

this is part of my config, then I encountered TypeError: Cannot read property 'statements' of undefined. If I replace "src/app/Market/components/Cloud/Item.js" to "global" , everything is OK

[SimenB]

Itæs not released yet - use jest@test or wait for #4948

[github-actions]

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