fix(cloneIncomingMessage): inherit prototype properties

[hrsh7th]

Fix #212

The current implementation will clone the properties defined in instance.
But the headers property defined in prototype in Node.js v16 or higher.

So this PR aims to support prototype inheriting in cloneIncomingMessage.

The final pitfalls is this is not support instanceof IncomingMessage and instanceof PassThrough. If the msw uses those operators, I think this must not be merged.

Fixed.

[kettanaito]

Hey, @hrsh7th! Thank you for submitting this fix.

The final pitfalls is this is not support instanceof IncomingMessage and instanceof PassThrough

This may be an issue, as we're exposing the cloned IncomingMessage publicly:

interceptors/src/interceptors/ClientRequest/NodeClientRequest.ts

Line 238 in 4563ce7

return super.emit(event, firstClone, ...data.slice(1))

When the consumer adds a response listener on ClientRequest, they will get the cloned message when using this library. They may have instanceof and other logic around that, which will break with this change if I understand correctly.

Maybe we can think of reusing parts of your solution to preserve the prototype? Would that be possible?

[trevoro]

I've tested this locally on node16 re-using the same workflow that the github actions has and it works great!

Regarding the types, this function as it existed before and after this PR forces the type by casting to unknown and then to ClonedIncomingMessage. The stream itself has the same overall shape but it now has the prototype methods added in. If you remove the 'to unknown' part tsc has a way better idea about the type of the stream and it seems like it's been the wrong one for quite some time. Like if you look at the shape of an IncomingMessage vs what's there in main it's not the same at all. I think that's out of scope of this issue for now though.

[hrsh7th]

I'd changed the implementation to support stream instanceof IncomingMessage.

This approach can be broken if both IncomingMessage and PassThrough have the same properties in different implementations. (This fact is the same in the existing implementation. So I think we have not to care about it in this PR for now)

[hrsh7th]

I think this PR is ready to review and merge. 👍🏼

[kettanaito]

I'm adding assertions to check that the cloned message indeed extends all the prototypes of the original message.

[kettanaito]

Absolutely fantastic job on this one, @hrsh7th! 🎉
Thank you for making this library better. Welcome to contributors!

[github-actions]

🎉 This PR is included in version 0.13.6 🎉

The release is available on:

• npm package (@latest dist-tag)
• GitHub release

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[hrsh7th]

Thank you for review, fix and merge! 🎉