jests async wrapper leaks memory

[Swatinem]

🐛 Bug Report

Possibly related to: #6814 and other reports of memory leaks…

I do have quite severe memory leaks, because one of our modules is super big (it imports a translation dictionary in multiple languages).
Each test file which imports that module blows up jests memory usage by ~20M.

While debugging the memory leak, I noticed that the translation dictionary is kept alive through jests asyncJestTest, which holds onto the closure fn.

I tried just unsetting fn after calling it, which worked for the asyncJestTest, but was failing for asyncJestLifecycle for some reason.

    TypeError: Cannot read property 'call' of null

      at Object.asyncJestLifecycle (node_modules/jest-jasmine2/build/jasmineAsyncInstall.js:51:37)

Oh, I get it… most likely because those lifecycles are called multiple times, haha.

To Reproduce

Steps to reproduce the behavior:

Use async functions for tests and lifecycle hooks that reference large objects :-)

Expected behavior

Jest should not leak! It should clean up all the async functions properly when a test file is finished.

Link to repl or repo (highly encouraged)

envinfo

[thymikee]

I wonder if it also happens with jest-circus? https://github.com/facebook/jest/tree/master/packages/jest-circus

[Swatinem]

Haven’t tried it yet, will do so tomorrow. Lets see how easy it is to integrate… We have a quite complex setup, also browsing through the issues, I’m not sure how production ready it already is?

[thymikee]

It is production ready, but has differences from jasmine

[Swatinem]

Just tried jest-circus, and it also leaks per-testfile. I haven’t looked at the memory profile itself to see where/why all the memory is retained, so it could as well be for some other reason.
All-in-all, the memory usage with jest-circus is even worse. Whereas our memory usage peaks at ~880M with --runInBand and the default runner, jest-circus peaks at >1200M before it goes OOM.

[thymikee]

The circus memory issue is tracked here: #8816.
cc @scotthovestadt

[SimenB]

If this is still an issue using the latest version of Jest (27 at the time of writing), please provide a reproduction we can pull down and test. The leak mentioned above has been fixed 🙂

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