jest-worker and typescript unexpected behavior

[tedconn]

🐛 Bug Report

Jest tests fail with this error:

Call retries were exceeded

      at ChildProcessWorker.initialize (node_modules/jest-worker/build/workers/ChildProcessWorker.js:193:21)

...

Jest did not exit one second after the test run has completed.

This usually means that there are asynchronous operations that weren't stopped in your tests. Consider running Jest with `--detectOpenHandles` to troubleshoot this issue.

To Reproduce

Using jest and @babel/preset-typescript, and jest-worker, create a test which creates a new jest-worker which invokes a typescript definition.

Expected behavior

The typescript worker is run without error and the result returned to the test

Link to repl or repo (highly encouraged)

Repro is here:
https://github.com/tedconn/worker-jest-ts

I was actually trying to repro a different issue but when trying to come up with a repro I would have expected this simple case to work!

envinfo

System:
    OS: macOS 10.14.6
    CPU: (12) x64 Intel(R) Core(TM) i7-8850H CPU @ 2.60GHz
  Binaries:
    Node: 12.9.0 - ~/.nvm/versions/node/v12.9.0/bin/node
    Yarn: 1.13.0 - /usr/local/bin/yarn
    npm: 6.10.2 - ~/.nvm/versions/node/v12.9.0/bin/npm
  npmPackages:
    jest: ^24.9.0 => 24.9.0 

[SimenB]

Could you add a readme to the reproduction with which commands to run in order to reproduce the bug, and describe what behaviour you expected?

[tedconn]

@SimenB done: https://github.com/tedconn/worker-jest-ts

[SimenB]

Thanks for the small reproduction!

The underlying cause of the error here is that jest-worker does not transpile the module passed to it. So you need to either transpile beforehand or use something like pirates.

The bad error message is because jest-worker by default passes silent: true when forking: https://github.com/facebook/jest/blob/8c169d20add61c8831162d8347d2710c07b6b0ef/packages/jest-worker/src/workers/ChildProcessWorker.ts#L93 & https://github.com/facebook/jest/blob/8c169d20add61c8831162d8347d2710c07b6b0ef/packages/jest-worker/src/workers/NodeThreadsWorker.ts#L74.
Jest itself then pipes stdout and stderr manually in the parent: https://github.com/facebook/jest/blob/8c169d20add61c8831162d8347d2710c07b6b0ef/packages/jest-runner/src/index.ts#L138-L139

To see the syntax error, either pass forkOptions: { silent: false } when instantiating the Worker, or do the same pipe thing that jest does.

Doing either of those will bubble up the syntax error:

---

We can probably improve our docs here. Ideas on how we could have made this clearer in the readme?

/cc @thymikee @jeysal

[thymikee]

A note in the docs & readme should be just enough. @tedconn would you like to contribute it?

[tedconn]

Thanks for the follow up.

I can contribute that.

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