fix(jest-worker): Remove circular references from messages sent to workers

[ziacik]

Fixes #10577

Summary

This fix prevents objects with circular references to be sent to worker processes. Node uses JSON.stringify to serialize such messages and this causes an error in case there are circular references in the messages.

Please note I added new dependency, fclone, though I'm not sure it's allowed or if there already is another such function in the repository.

Test plan

This fix allows to run the tests described in the issue linked. The repro setup can be found at https://repl.it/@Frantiekiaik/jest-playground-1.

[SimenB]

We'd want to restore the original object on the receiving side, no? Should we use something like https://github.com/storybookjs/telejson?

[ziacik]

@SimenB sounds reasonable. I'll try to rework.

[MichaReiser]

Would the 'advanced' serialization format be an alternative for use-cases that require circular references to avoid that all workers must pay for the overhead of fclone? This would also solve the issue where e.g. a child returns a structure containing circular references.

I would suggest to not enable this option by default because it comes with a slight performance overhead.

[SimenB]

@MichaReiser I tried that, but it just changes the error to the same as worker threads

(node:24057) UnhandledPromiseRejectionWarning: Error: () =>
          (0, _jestMatcherUtils.matcherHint)(
            matcherName,
            undefined,
           ...<omitted>... ) could not be cloned.
    at writeChannelMessage (internal/child_process/serialization.js:79:9)
    at process.target._send (internal/child_process.js:805:17)
    at process.target.send (internal/child_process.js:703:19)
    at reportSuccess (/Users/simen/repos/jest/packages/jest-worker/build/workers/processChild.js:67:11)

While using worker (which uses structured clone by default)

(node:24148) UnhandledPromiseRejectionWarning: DataCloneError: () =>
          (0, _jestMatcherUtils.matcherHint)(
            matcherName,
            undefined,
           ...<omitted>... ) could not be cloned.
    at reportSuccess (/Users/simen/repos/jest/packages/jest-worker/build/workers/threadChild.js:77:32)

[MichaReiser]

@SimenB that's rather interesting because the MDN documentation explicitly mentions circular references...

The structured clone algorithm copies complex JavaScript objects. It is used internally to transfer data between Workers via postMessage(), storing objects with IndexedDB, or copying objects for other APIs. It clones by recursing through the input object while maintaining a map of previously visited references, to avoid infinitely traversing cycles. source.

What kind of object did you pass? Any chance it did use Proxies, contained Symbols, or used other features that make it not a plain JS object? spec

However, it is as it is. I still believe that it would make sense to change jest worker to allow passing in a custom serializer / deserialiser instead of requiring a custom serialization logic for all clients. Or manually calling fclone before invoking the method on the jest-worker / reading the value in the worker. E.g. I personally would prefer to get an error than being surprised by the fact that some properties in the worker/ in the result have been changed to [Circular] for no obvious reasons.

[SimenB]

I've opened up #10981 which uses telejson and should restore the object "on the other side". I haven't dug into why passing circular objects doesn't work. Might be a good idea to do so as there's probably less overhead in fixing the object we pass (if possible) rather than adding custom serialization and deserialization

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