Syntax error when running Jest with coverage and watch (example repo included)

🐛 Bug Report

This bug is likely the same as #6258.

In some cases, when I run jest --coverage --watch, I get the following error:

Running coverage on untested files...Failed to collect coverage from /Users/gary/Downloads/Unsorted/test/jest-bug/package.json
ERROR: Unexpected token, expected ; (2:8)
STACK: SyntaxError: Unexpected token, expected ; (2:8)

To Reproduce

Steps to reproduce the behavior:

1. Clone this repo.
2. Create a new branch from master. Reset HEAD to the commit before HEAD (“add package.json and yarn.lock”), but keep the changes, and unstage them. So now you have a.test.js uncommitted, and package.json has "name": "test" uncommitted.
3. Run yarn test-w. You will get the same error.

I assume the cause is because:

1. coverage is enabled. It has to be via Jest config collectCoverage: true, and not CLI --coverage.
2. watch is enabled (and it possibly also occurs with watch-all), so only uncommitted changes are watched. In order to reproduce this bug, there needs to be changes to a test file, and changes in a non-JS file, like .eslintrc.json or package.json.
3. This is actually a pretty common scenario, at least for me, so I get this error a lot.

Expected behavior

The error should not happen.

Link to repl or repo (highly encouraged)

The repo is linked to in step 1 of “Reproduce” section above.

Run npx envinfo --preset jest

Paste the results here:

  System:
    OS: macOS High Sierra 10.13.5
    CPU: x64 Intel(R) Core(TM) i7-3615QM CPU @ 2.30GHz
  Binaries:
    Node: 8.11.2 - /usr/local/bin/node
    Yarn: 1.9.4 - /usr/local/bin/yarn
    npm: 6.4.0 - /usr/local/bin/npm
  npmPackages:
    jest: ^23.5.0 => 23.5.0

The bug does not exist in 22.4.4. The bug exists in 23.0.0.

Unfortunately, I can’t downgrade to Jest 22 for now, since that version has the jsdom errors instead.

[rodgobbi]

My team was having this problem too, even without the watch mode or trying to use collectCoverage: true. My teammate discovered this solution: Put into the jest config

"jest": {
  ...
  "coveragePathIgnorePatterns": [
    "/node_modules/",
    "testconfig.js",
     ... (any file that doesn't need coverage check but is targeted by the coverage report)
    "package.json",
    "package-lock.json"
  ],
}

[stipsan]

@SimenB sure I’ll take a look 😄