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fix(fetch): respect "abort" event on the request signal #394

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merged 15 commits into from
Sep 2, 2023
Merged

fix(fetch): respect "abort" event on the request signal #394

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52aa901
fix: abort request if the user aborts it
JesusTheHun Jul 25, 2023
d48c61a
fix: reject user request with native error instead of wrapper error
JesusTheHun Aug 29, 2023
8e229ca
docs: fix request typo in readme (#404)
Aug 25, 2023
96e1685
chore: migrate to pnpm (#407)
kettanaito Aug 28, 2023
94a2a59
fix: set "X-Request-Id" header in XMLHttpRequest only in Node.js (#397)
avivasyuta Aug 28, 2023
e0ca09d
Merge branch 'main' into fix/honor-abort-signals
kettanaito Aug 30, 2023
864a06e
test: move fetch abort controller compliance test
kettanaito Aug 30, 2023
faff151
fix: forward abort reason
JesusTheHun Aug 30, 2023
4753f13
fix: split request rejection logic
JesusTheHun Aug 30, 2023
46dd281
chore(fetch): reject request with request abort rejection reason
kettanaito Aug 30, 2023
e5818a1
Merge branch 'main' into fix/honor-abort-signals
kettanaito Aug 30, 2023
f57fcf9
Merge branch 'main' into fix/honor-abort-signals
kettanaito Sep 1, 2023
b5e4db9
fix: listen to "abort" event once
kettanaito Sep 1, 2023
5470be2
chore: remove log from test
kettanaito Sep 1, 2023
25ad663
Merge branch 'main' into fix/honor-abort-signals
kettanaito Sep 2, 2023
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9 changes: 8 additions & 1 deletion src/interceptors/fetch/index.ts
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Original file line number Diff line number Diff line change
Expand Up @@ -70,10 +70,17 @@ export class FetchInterceptor extends Interceptor<HttpRequestEventMap> {
return mockedResponse
})

if (resolverResult.error || requestAbortRejection.state === 'rejected') {
if (requestAbortRejection.state === 'rejected') {
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@kettanaito kettanaito Aug 30, 2023 •
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Do you think we should conceptually treat this promise as resolved instead?

If we imagine promise as an intention, then the intention here is to know when the request has been aborted by another actor. In that light, an aborted request would mean a resolved requestAborted promise.

It would make this check read much nicer as well. What are your thoughts on this?

I'm also a bit hesitant to base this condition on the request abort promise itself. I'd rather we used that promise in the Promise.race() but handled the resolverResult.error differently. This implies that requestAbortRejection can still throw but it does so with a custom error/object that is later checked on the resolverResult.error:

signal.addEventListener('abort', () => {
  requestAbortRejection.reject({ type: 'aborted', reason: signal.reason })
})

if (resolverResult.error) {
  if (resolverResult.error.type === 'aborted') {
    return Promise.reject(resolverResult.error.reason)
  }

  return /* create the TypeError, set "cause" */
}

We can also use a custom AbortError class to prevent any false positives here since it's possible for the user to abort a request with a compatible object as the reason.

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It is true that the promise encapsulate the expectation of an aborted request.
Resolving it would mean that the expectation has been reached, which is logically correct.
However, in our case, we use a promise as a poor man's event : the promise rejection carries no expectation and therefore no logical meaning. We just want to be notified when the abortion happens.
From there, this promise is a mere async tool.
Resolving it, then check the race winner, then throw a custom object, check the resolverResult resolution value, all of that to ultimately throw the error we had in the first place, seems unnecessary to me.
On a side note, in the end, I'm not the maintainer of the project, if you feel more comfortable with this extra layer, do it, this is your call :)

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Thanks for your input. I agree that it's mainly a semantic difference. We can leave it rejecting as-is. On the second half, I will lean toward making the resolver handling more streamlined, handling it by what the until returns instead of relying on external factors like the rejection promise. I will push the change shortly.

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Actually my point is that this is not a semantic difference but a technical one. We expect something to happen, using resolve or reject make no difference. If our expectation could fail then it would make a semantic difference.

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I ended up leaving the explicit rejection promise check but instead of coupling the request rejection promise and the resolver error, I reject the request promise with the abort rejection reason. Also, that is hell of a sentence to write.

return Promise.reject(resolverResult.error)
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I believe this is incorrect. I copied the previous behavior from Undici and we must comply by it. Note that the FetchInterceptor is primarily meant for Node, and I trust Undici implement the spec rather faithfully.

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I'd suggest we revert this particular change for now because it's not related to the abort controller support. We can discuss it as a separate improvement point, what do you think?

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I checked the Undici implementation and there are only two causes of error : abortion and network issue.
Since the abortion error is well defined (specific class and specific error code), we can check the error type and reject accordingly.
If we don't do that, we deviate from production behavior.

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I agree, we should do it the same way: handle the two error scenarios separately:

  • Keep what you've introduced for abort errors.
  • Revert what was there previously (the TypeError) to handle all the other errors (effectively, network errors).

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This is what I've done in my latest commit ;)

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Thanks so much for addressing it so quickly! Will give it the last round of review and let's get this published.

}

if (resolverResult.error) {
const error = Object.assign(new TypeError('Failed to fetch'), {
cause: resolverResult.error,
})
return Promise.reject(error)
}

const mockedResponse = resolverResult.data

if (mockedResponse && !request.signal?.aborted) {
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33 changes: 31 additions & 2 deletions test/modules/fetch/compliance/abort-conrtoller.test.ts
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Original file line number Diff line number Diff line change
Expand Up @@ -54,7 +54,35 @@ it('aborts unsent request when the original request is aborted', async () => {
expect(abortError.message).toBe('This operation was aborted')
})

it('forwards custom abort reason to the aborted request', async () => {

it('aborts a pending request when the original request is aborted', async () => {
const requestListenerCalled = new DeferredPromise<void>()
const requestAborted = new DeferredPromise<Error>()

interceptor.on('request', async ({ request }) => {
requestListenerCalled.resolve()
await sleep(1_000)
request.respondWith(new Response())
})

const controller = new AbortController()
const request = fetch(httpServer.http.url('/delayed'), {
signal: controller.signal,
}).then(() => {
expect.fail('must not return any response')
})

request.catch(requestAborted.resolve)
await requestListenerCalled

controller.abort()

const abortError = await requestAborted
expect(abortError.name).toBe('AbortError')
expect(abortError.message).toBe('This operation was aborted')
})

it('forwards custom abort reason to the request if aborted before it starts', async () => {
interceptor.on('request', () => {
expect.fail('must not sent the request')
})
Expand All @@ -77,7 +105,8 @@ it('forwards custom abort reason to the aborted request', async () => {
expect(abortError.message).toBe('Custom abort reason')
})

it('aborts a pending request when the original request is aborted', async () => {

it('forwards custom abort reason to the request if pending', async () => {
const requestListenerCalled = new DeferredPromise<void>()
const requestAborted = new DeferredPromise<Error>()

Expand Down