Support nodejs worker_threads

[TimDaub]

Scope

Improves an existing behavior

Compatibility

• This is a breaking change

Feature description

In Discord, I asked:

Hey I'm using msw in nodejs. I'm doing fetch requests in a worker_thread, will msw intercept those?

The response was:

Hey, @tim . Currently no. We have support for interception in a child process but it's not a part of MSW yet, as far as I know.

So this issue is documenting that worker_threads aren't supported currently.

Details that could help during implementation:

Regarding child process interception, you can read how it functions right now in here: https://github.com/mswjs/interceptors#remotehttpinterceptor
Shortly: you establish an interceptor in a child process, and a remote resolver in a parent process. Then the library uses IPC to message requests/responses between the processes.

[kettanaito]

Hi, @TimDaub. Thanks for this proposal.

That response appears to be correct. We support request interception via IPC in the low-level Interceptors library but not as a part of MSW (yet). If you wish to enable API mocking in your worker, you would have to follow the Node.js integration and set it up in that worker. You won't have the means to affect the library's behavior from a parent process at the moment.

We are exploring a better experience around this but this has a low at the moment.