support AbortSignal.reason
#1775
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In enviroments that implement it. When an `AbortSignal#reason` has a value, i.e. in nodejs >= v17.2.0, it is added on the returned `AbortError`. `AbortError#reason` would be `undefined` otherwise. Contary to the specification, when `AbortController#abort` is called, with or without a reason, `fetch` _does not_ throw the `AbortSignal#reason`.
LinusU
reviewed
Oct 2, 2023
| * AbortError interface for cancelled requests | ||
| */ | ||
| export class AbortError extends FetchBaseError { | ||
| constructor(message, type = 'aborted') { |
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Is this a breaking change?
AbortError is exported publicly from the package...
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Yeah, wasn't aware the constructor was actually exported. It just seemed odd that the type would be explicitly given, i.e. what else could it be.
We basically need to thread the reason into the thrown AbortError. To not break its constructor, the only sane option would be to extend it:
// no change to existing `AbortError`
class AbortWithReasonError extends AbortError {
constructor(message, reason) {
super(message);
this.reason = reason;
}
}
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In enviroments that implement it.
When an
AbortSignal#reasonhas a value, i.e. in nodejs >= v17.2.0, it is added on the returnedAbortError.AbortError#reasonwould beundefinedotherwise.Contrary to the specification, when
AbortController#abortis called, with or without a reason,fetchdoes not throw theAbortSignal#reason. This is to allow more fine grained error handling. Had thereasonwas thrown, the general information that an abort happened is lost and it becomes sole responsibility of the reason provider.Purpose
Allow detecting the reason fetch was aborted.
Changes
AbortErrorto have fieldreason. It's constructor takes this additional argument.AbortSignal#reasonis given when constructingAbortErrorinstance. Could possibly beundefinedin environments/libraries/polyfills that do not support it.Additional information
The actual value (even existence) of
AbortSignal#reasonis external to this library. We make no assumptions about it. We simply forward it.This goes against #1519. There is no inherent reason to follow the specifications to the dot.
node-fetchis for node, specifically, not the web. TBD.