collectCoverage breaks TypeScript source stepping

[mikebm]

Do you want to request a feature or report a bug?
BUG

What is the current behavior?
When collectCoverage is set to true, then source stepping no longer functions correctly.

Steps:
git clone https://github.com/mikebm/jestbug.git
cd jestbug
npm install
Debug the ./tests/component.test.ts file. Attempt to step through the executeSomeLogic call on test 'should return 5'.

What is the expected behavior?
When stepping through the executeSomeLogic function, your debugger should show the correct line that you are on.

Please provide your exact Jest configuration and mention your Jest, node,
yarn/npm version and operating system.
Node v8.9.0
Jest 22.4.2
npm 5.6.0

[mikebm]

Note: The repo has been updated with decorators to prove a separate ts-jest line reporting issue. This issue is still reproducible with and without the decorators.

[SimenB]

Is this still an issue with the latest Jest and ts-jest?

[mikebm]

Yes, it is still an issue. I just tested with jest 23.6.0. I upgraded the test project as well.

[SimenB]

@huafu ideas?

[huafu]

I first thought it was related to: babel/babel#6577 but after some tests doesn't seem to be (@SimenB you can confirm that bare js instrumented thru jest do can be debugged step by step when coverage is on right?). In ts-jest we do patch it, but only if babel is required. I tried to patch it beforehand without success.

We do have e2e tests running over multiple versions of jest, babel and typescript for source mapping and then coverage, but I believe we do not have for both together, will drop an eye tommo.

@mikebm can you open an issue on ts-jest with the link to your repo, I'll try to look at it asap. We're about to publish a new release but it'll wait if this is indeed ts-jest related and if it can get fixed quickly.

BTW, your jest config can be simplified a lot @mikebm:

{
  "preset": "ts-jest",
  "automock": true,
  "collectCoverage": true,
  "coverageDirectory": "<rootDir>/coverage/jest",
  "coverageReporters": ["lcov", "json"],
  "resetMocks": true,
  "resetModules": true,
  "testResultsProcessor": "jest-junit-reporter"
}

[huafu]

Ok so this is a jest bug and not ts-jest bug.

First here you're losing the input source maps in case it's not inlined but in the map property:

https://github.com/facebook/jest/blob/0cd757b71cef7aec07c9532f7b64739cc8baeb1f/packages/jest-runtime/src/script_transformer.js#L246

Then even if you had the source maps inlined, it'd be lost anyway there:

https://github.com/facebook/jest/blob/0cd757b71cef7aec07c9532f7b64739cc8baeb1f/packages/jest-runtime/src/script_transformer.js#L155-L171

...where useInlineSourceMaps is false, and even tho, no possibly generated source maps is returned.

I'll try to provide a PR here soon.

Update: the title of this issue should be: enabling coverages breaks source maps – it's not only for typescript.

[SimenB]

There's probably a reason why we don't factor in the source map in that case. @jwbay @aaronabramov do you know if there are?

[huafu]

@SimenB any news on this? I meant, I'd be happy to provide a PR but I'm not gonna try if there is a good reason for it to be like that ;-)

[SimenB]

Feel free to send a PR! I'm not sure how it works, but if we're able to show it's more correct, no reason not to merge it 🙂

[ruiaraujo]

@huafu any chance of doing the PR?

[huafu]

@ruiaraujo I actually had to run on another thing, and my project to hurry to finish. I have started a PR, AFAIR it was not as hard as I thought, ...was harder.

So no, not finished, and now can't even remember what was the issue I was stuck with.

FYI this is my branch, but I think I started again from sratch locally. Anyway, could give you the idea of what should be done.

I'm sorry it's not in my priority because you can always run without coverage on your local while debugging and add --coverage for the final run (or the unique on CI) to have coverage.