fix: Determining `inheritedMetadatas` during jest+ts-jest tests collects metadatas that do not belong to the target

[sdokara]

Description

This is a very edge-casey situation that I ran into.

I have a web service project in typescript@4.9.3 on Node 16 with typeorm@0.2.32 classes being decorated. Everything runs perfectly in normal mode: tsc transpiles stuff and node runs it without issues. The validator collects the metadata properly.
But, when running tests with jest that uses ts-jest as the transformer (with default configuration), the transpiled output acts kinda weird.

For all decorated classes, in src/metadata/MetadataStorage.ts:109, when computing inheritedMetadatas, there's an if:

if (metadata.target instanceof Function && !(targetConstructor.prototype instanceof metadata.target))
    return false;

Now, during tests, metadata.target instanceof Function yields false even though it is the class and typeof metadata.target does indeed yield 'function'. I have no idea how this is happening. I'm able to monkey-patch it by using typeof.

This used to work with older versions of my dependencies, but I wasn't able to pinpoint the culprit.

[mzpeartx]

I am seeing a similar behavior. My current workaround was to downgrade to version 0.11.1.

[NoNameProvided]

I would guess this is due to a difference in how ts-jest compiles the code and you probably need to add some options to your test config.

I have some faded memories of someone having a similar issue quite some time ago, but there the problem was a change in babel transform that strips the metadata. Maybe you are affected by the same problem?

[mzpeartx]

@NoNameProvided That makes sense. I'll have to do a little digging, thanks for the suggestion!

[NoNameProvided]

Closing this as invalid. I cannot provide support with general programming-related questions.

I hope you will find the bug.

[github-actions]

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