DOM: Reorder Observable completion events #44682
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This CL "fixes" Observable unsubscription/teardown timing. As a matter
of accidental historical precedent, Observables in JavaScript (but not
in other languages) had implemented the "rule" that upon
Subscriber#error() or Subscriber#complete(), the subscriber would:
1. First, invoke the appropriate Observer callback, if provided (i.e.,
complete() or error() callback).
2. Signal abort Subscriber#signal, which invokes any teardowns and also
fires the `abort` event at the signal.
However, after dom@chromium.org discussed this more with
ben@benlesh.com, we came to the conclusion that the principle of "as
soon as you know you will teardown, you MUST close the subscription and
any upstream subscriptions" should be adhered. This means the above
steps must be inverted. This is a small-in-size but medium-in-impact
design change for the Observable concept, and led to a blog post [1] and
an announcement [2] that the RxJS library intends to change its
historical ordering of these events.
This CL:
1. Inverts the order of the aforementioned steps in the Blink
implementation.
2. Improves some tests that assert this new ordering.
3. Simplifies the takeUntil() operator in general.
The Observable spec will be updated alongside this commit:
WICG/observable#120.
[1]: https://benlesh.com/posts/observables-are-broken-and-so-is-javascript/
[2]: ReactiveX/rxjs#7443
R=masonf@chromium.org
Bug: 1485981
Change-Id: I376e66eef490808d264dc999862a801d591aa278
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/5311097
Commit-Queue: Dominic Farolino <dom@chromium.org>
Reviewed-by: Mason Freed <masonf@chromium.org>
Cr-Commit-Position: refs/heads/main@{#1263562}
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This CL "fixes" Observable unsubscription/teardown timing. As a matter
of accidental historical precedent, Observables in JavaScript (but not
in other languages) had implemented the "rule" that upon
Subscriber#error() or Subscriber#complete(), the subscriber would:
complete() or error() callback).
fires the
abortevent at the signal.However, after dom@chromium.org discussed this more with
ben@benlesh.com, we came to the conclusion that the principle of "as
soon as you know you will teardown, you MUST close the subscription and
any upstream subscriptions" should be adhered. This means the above
steps must be inverted. This is a small-in-size but medium-in-impact
design change for the Observable concept, and led to a blog post 1 and
an announcement 2 that the RxJS library intends to change its
historical ordering of these events.
This CL:
implementation.
The Observable spec will be updated alongside this commit:
WICG/observable#120.
R=masonf@chromium.org
Bug: 1485981
Change-Id: I376e66eef490808d264dc999862a801d591aa278
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/5311097
Commit-Queue: Dominic Farolino <dom@chromium.org>
Reviewed-by: Mason Freed <masonf@chromium.org>
Cr-Commit-Position: refs/heads/main@{#1263562}