fix: Error Cannot read property converageData of null #7758

[c0d3m3nt0r]

Summary

This PR is meant to fix #7758. In the provided GitHub issue link there are repro steps, also an explanation of the fix applied in this PR #7758 (comment).

Test plan

A new pair of tests were added to cover these changes.

Jest Output:

➜  jest git:(fix-cannot-read-property-converageData-of-null) yarn jest-coverage -u packages/jest-reporters/src/__tests__/generateEmptyCoverage.test.js
yarn run v1.15.0
$ yarn jest --coverage -u packages/jest-reporters/src/__tests__/generateEmptyCoverage.test.js
$ node ./packages/jest-cli/bin/jest.js --coverage -u packages/jest-reporters/src/__tests__/generateEmptyCoverage.test.js
 PASS  packages/jest-reporters/src/__tests__/generateEmptyCoverage.test.js
  generateEmptyCoverage
    ✓ generates an empty coverage object for a file without running it (516ms)
    ✓ generates a null coverage result when using /* istanbul ignore file */ (53ms)
    ✓ generates a null coverage result when collectCoverage global config is false (1ms)

Coverage Output:

-----------------------------------------------|----------|----------|----------|----------|-------------------|
File                                           |  % Stmts | % Branch |  % Funcs |  % Lines | Uncovered Line #s |
-----------------------------------------------|----------|----------|----------|----------|-------------------|
generateEmptyCoverage.ts                       |      100 |    83.33 |      100 |      100 |                47 |
...

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[c0d3m3nt0r]

@SimenB,

We have the same issue described in #7758 in our current application setup, with the following dependencies:

"jest": "^24.5.0",
"jest-haste-map": "^24.5.0",
"babel-jest": "^24.5.0"

Changes in this PR fix the issue. In addition I have added a couple more tests, and everything looks good from our side.

Let me know what do you think.

Thank you!

[codecov-io]

Codecov Report

Merging #8168 into master will increase coverage by 0.02%.
The diff coverage is 80%.

@@            Coverage Diff             @@
##           master    #8168      +/-   ##
==========================================
+ Coverage   62.24%   62.26%   +0.02%     
==========================================
  Files         265      265              
  Lines       10448    10450       +2     
  Branches     2540     2541       +1     
==========================================
+ Hits         6503     6507       +4     
+ Misses       3360     3359       -1     
+ Partials      585      584       -1

Impacted Files	Coverage Δ
...ckages/jest-reporters/src/generateEmptyCoverage.ts	90% <80%> (+27.5%)	⬆️

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[SimenB]

Looks great, thank you for tackling it!

Can you update the changelog and sign the CLA, and I can merge this 🙂

[kachkaev]

If 24.6.0 is somewhat away, it'd be awesome to have this fix in 24.5.1 🙏 The bug is blocking us from upgrading from Jest 23 and we can't wait to do this! @c0d3m3nt0r many thanks for your your time and effort! 🙌

[c0d3m3nt0r]

@thymikee, @SimenB, thank you for taking the time to review and merge these changes!, we will be waiting for them to be released.

@kachkaev, no problem!

[vicapow]

@c0d3m3nt0r Still planning on publish this with 24.5.1 ? This is also preventing us from updating :/

[SimenB]

A release is coming when we land the open PRs with performance improvements :)

[kachkaev]

Seems like all pull requests mentioning Performance in their title have been merged 👀🙌 Well, at least the ones that were at the top of the PR list 😁

[kachkaev]

Can it be that because of this PR files that have zero covered lines are now totally ignored? I noticed a significantly higher coverage percentage after upgrading from 23 to 24 and then realised that uncovered files are simply removed from the reports 🤔

[SimenB]

That might very well be! Would you be able to put together a reproduction?

[kachkaev]

Only seeing this in our team's gigantic repo for now. Will try producing an MWE and submitting an issue 😉

[kachkaev]

It may well be that our collectCoverageFrom RegExp simply broke after upgrading from 23 to 24 (something to do with micromatch upgrade in #6650?). At least I cannot reproduce the bug in a new test project:

## Try collecting coverage with Jest 24

# cd new-empty-folder

cat << EOF > package.json
{
  "jest": {
    "collectCoverageFrom": [
      "src/**/*.js"
    ]
  }
}
EOF

cat << EOF > .babelrc
{ "presets": ["@babel/preset-env"] }
EOF

yarn add --dev @babel/core @babel/preset-env jest

mkdir src

cat << EOF > src/a.js
export default () => "a";
EOF

cat << EOF > src/b.js
export default () => "b";
EOF

cat << EOF > src/b.test.js
import b from "./b";
test("b works", () => {
  expect(b()).toEqual("b");
});
EOF

yarn jest --coverage

## Downgrade to Jest 23

yarn remove --dev @babel/core @babel/preset-env jest
yarn add --dev babel-core babel-preset-es2015 jest@23
cat << EOF > .babelrc
{ "presets": ["es2015"] }
EOF

yarn jest --coverage

Both source files (a.js and b.js) are included into the coverage report in Jest 24 just as in Jest 23. I'll try checking again tomorrow when I'm back at work 😉

[kachkaev]

Strange, but in the monorepo where I spotted the issue in the first place, collectCoverageFrom still does not work. It's defined as ["src/**/*.{js,jsx,ts,tsx}"], I tried ["<rootDir>/src/**/*.{js,jsx,ts,tsx}"] and ["**/*.{js,jsx,ts,tsx}"]. The coverage is collected, but only for the files that have at least line covered (as if collectCoverageFrom was not defined).

Related issue: #8207

[github-actions]

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