Add "continue" helper

[kentcdodds]

Scope

Adds a new behavior

Compatibility

• This is a breaking change

Feature description

I would like to be able to do this:

	const email = faker.internet.email()
	let emailRequest: Request
	server.use(
		rest.post(`https://api.resend.com/emails`, async ({ request }) => {
			emailRequest = request
			return continue()
		}),
	)

This would allow me to override the handler just to get the request so I can make assertions on it, but then let msw continue to look for another existing handler that will handle this request.

[kettanaito]

Hi, @kentcdodds. The fallthrough behavior is already implemented and it's the default behavior MSW exhibits.

Fallthrough in 1.x

In version 1.x, it's enough to return undefined from the resolver to tell MSW to keep looking for any other matching handler.

rest.get('/resource', (req, res, ctx) => {
  // ...any side-effects.
  return
})

Fallthrough in 2.x (#1404)

In version 2.x, it works the same way: MSW keeps iterating until it meets a handler that returns a response:

msw/src/core/utils/getResponse.ts

Lines 36 to 43 in 90b854a

	// Stop the lookup if this handler returns a mocked response.
	// If it doesn't, it will still be considered the last matching
	// handler until any of them returns a response. This way we can
	// distinguish between fallthrough handlers without responses
	// and the lack of a matching handler.
	if (result?.response) {
	break
	}

Did you experience an issue with this behavior? I'm rather confident it's stable in 1.x but I might have introduced a regression in the 2.x rewrite. If that's the case, please let me know. Thanks.

[kentcdodds]

Ah! That makes plenty of sense. I'll test it out and let you know if I have issues. I guess I forgot about this behavior 😅