msw: allow passthrough for undefined routes / graphql interferes with passthrough

thanks @kettanaito , just upgraded to 0.20.5 and it works without the empty handlers!

@kettanaito I could use this feature as well for testcafe support. testcafe has some internal posts it makes back to it’s proxy server, and we can’t add headers to those requests. I noticed that if i just add resolve(getOriginalResponse()); to the INTERNAL_ERROR handler in mockServiceWorker.js it works, but that felt wrong to do.

Thanks @kettanaito ! Yes looks like I was also searching for “passthrough” and not “bypass” 😦

returning nothing definitely works! – although I did not understand this from the docs, and also I get type errors using your solution – I got around it by:

  (rest as any).post('https://my.auth0.com/oauth/token', () => {
    return;
  }),

Here’s the type error with using any

 Type 'void' is not assignable to type 'MockedResponse | Promise<MockedResponse>'.ts(2345)

A couple things about the docs:

• some how I ended up on https://redd.gitbook.io/msw/api/compose-mocks thinking that was the official docs? it does have search functionality which is nice

• after finding mswjs.io/docs – I think bypass and (as I was searching “passthrough”) could be more prevalent.

I might also make it a default option on .start({ bypassUnmocked: true }) or something to that effect.

Returning nothing to bypass was not clear to me – I thought I needed to return ctx.fetch(req) as per https://redd.gitbook.io/msw/recipes/query-parameters#conditional-mocking

To answer your Q:

If I understand correctly, the absence of a request handler is what you mean by “for undefined routes”.

Yes, undefined routes might automatically be allowed passthrough based on that config setting. Similar to axios-mock-adapter has the passthrough option.

IE if absent handlers, then allow the original request to go through

Hey, @ilovett. Thanks for raising this.

Just to clarify: if your response resolver doesn’t return anything, that request will be bypassed, even if it matches a predicate. To illustrate, this should log out each GET request your app makes, while performing them as-is:

rest.get('*', (req, res, ctx) => {
  console.log(req.url.href)
  // Notice no `return res()` statement
})

You can utilize that behavior to conditionally short circuit in a resolver:

res.get('/auth', (req, res, ctx) => {
  if (someCondition) {
    // Return nothing, thus, bypassing this request
    return null
  }

  // Return a mocked response
  return res(...)
})

Also, any request that does not have a corresponding request handler is performed passthrough by default. If I understand correctly, the absence of a request handler is what you mean by “for undefined routes”. Did I get it correctly? (It would be very helpful if you included an example of what you are talking about, even if in pseudo-code).

An auth0 recipe may be helpful.

A good point 👍 We may have to list such recipe on the docs. Perhaps, even as an outcome of our discussion here!