refactor: show error message from jest-worker

[pustovalov]

This PR contains a:

• bugfix
• new feature
• code refactor
• test update
• typo fix
• metadata update

Motivation / Use-Case

#143 (comment)

 looks like bug in jest-worker

jestjs/jest#8872 (comment)

https://github.com/facebook/jest/blob/master/packages/jest-worker/src/workers/ChildProcessWorker.ts#L93

I think these changes will help to find a problem

Breaking Changes

Nope

Additional Info

[jsf-clabot]

All committers have signed the CLA.

[codecov]

Codecov Report

Merging #203 into master will increase coverage by <.01%.
The diff coverage is 100%.

@@            Coverage Diff             @@
##           master     #203      +/-   ##
==========================================
+ Coverage   98.44%   98.45%   +<.01%     
==========================================
  Files           7        7              
  Lines         387      388       +1     
  Branches      155      156       +1     
==========================================
+ Hits          381      382       +1     
  Misses          6        6

Impacted Files	Coverage Δ
src/TaskRunner.js	100% <100%> (ø)	⬆️

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[alexander-akait]

Thanks

[alexander-akait]

Can we add test(s) where we can see what an error appears?

[pustovalov]

I will try

[pustovalov]

When writing a test, I found silent:false doesn’t work, thanks to this demo: https://github.com/tedconn/worker-jest-ts

forkOptions: {
    silent: false,
},

[~/Downloads/worker-jest-ts-master]$ npm test                                                                                                                                        [ruby-2.6.1]

> worker-jest-ts@1.0.0 test /Users/pavel/Downloads/worker-jest-ts-master
> jest --forceExit

 FAIL  src/__tests__/index.test.js
  invokes the compiler
    ✕ prints the right message (262ms)

  ● invokes the compiler › prints the right message

    Call retries were exceeded

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

Test Suites: 1 failed, 1 total

Change silent: false to this one

if (worker.getStderr()) worker.getStderr().pipe(process.stderr)

result:

[~/Downloads/worker-jest-ts-master]$ npm test                                                                                                                                        [ruby-2.6.1]

> worker-jest-ts@1.0.0 test /Users/pavel/Downloads/worker-jest-ts-master
> jest --forceExit

/Users/pavel/Downloads/worker-jest-ts-master/src/compiler.ts:1
export async function compile() {
^^^^^^

SyntaxError: Unexpected token 'export'
    at wrapSafe (internal/modules/cjs/loader.js:1055:16)
    at Module._compile (internal/modules/cjs/loader.js:1103:27)
    at Object.Module._extensions..js (internal/modules/cjs/loader.js:1159:10)
    at Module.load (internal/modules/cjs/loader.js:988:32)
    at Function.Module._load (internal/modules/cjs/loader.js:896:14)
    at Module.require (internal/modules/cjs/loader.js:1028:19)
    at require (internal/modules/cjs/helpers.js:72:18)
    at execMethod (/Users/pavel/Downloads/worker-jest-ts-master/node_modules/jest-worker/build/workers/processChild.js:128:16)
    at process.<anonymous> (/Users/pavel/Downloads/worker-jest-ts-master/node_modules/jest-worker/build/workers/processChild.js:64:7)
    at process.emit (events.js:305:20)
/Users/pavel/Downloads/worker-jest-ts-master/src/compiler.ts:1
export async function compile() {
^^^^^^

  invokes the compiler
    ✕ prints the right message (289ms)

  ● invokes the compiler › prints the right message

    Call retries were exceeded

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

Test Suites: 1 failed, 1 total
Tests:       1 failed, 1 total

but even with if (worker.getStderr()) worker.getStderr().pipe(process.stderr) I did not find a way to write a test for this

If I put process.exit(1) to the worker.js, I see this an error:

  console.log src/TaskRunner.js:60
    er Error: Call retries were exceeded
        at ChildProcessWorker.initialize (/Users/pavel/terser-webpack-plugin/node_modules/jest-worker/build/workers/ChildProcessWorker.js:193:21)
        at ChildProcessWorker.onExit (/Users/pavel/terser-webpack-plugin/node_modules/jest-worker/build/workers/ChildProcessWorker.js:264:12)
        at ChildProcess.emit (events.js:305:20)
        at Process.ChildProcess._handle.onexit (internal/child_process.js:275:12) {
      type: 'WorkerError'
    }

I think we see this error because the process does not have enough memory and it crashes, maybe we can add some debug information to the
https://github.com/webpack-contrib/terser-webpack-plugin/blob/master/src/TaskRunner.js#L47

something like this

const showMemoryUsage = (step = '') => {
  const used = process.memoryUsage().heapUsed / 1024 / 1024;
  console.log(`Memory used ${step}: ${Math.round(used * 100) / 100} MB`);
};

showMemoryUsage('on worker error');

[alexander-akait]

In theory crash can be not only because of memory, I think we can then avoid the tests, let's just add comments to the code, why are we doing this

[pustovalov]

Changed the code from silent: false to this implementation:
https://github.com/facebook/jest/blob/v24.9.0/packages/jest-runner/src/index.ts#L138

[alexander-akait]

Big thanks!