Fix DoOnEach ASYNC fusion triggering onNext signal twice #3045
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This commit fixes the DoOnEachFuseableSubscriber to interpret any upstream onNext as a fusion trigger in ASYNC mode (onNext(null)). Furthermore, this commit fixes the Operators.MonoSubscriber handling of FUSED case. Since that abstract operator only supports ASYNC fusion, the FUSED_* states are renamed FUSED_ASYNC_*. In the drain loop, even in FUSED case the operator emits t downstream where it should emit null technically (again, because FUSED == ASYNC). This error is also fixed. Fixes #3044.
OlegDokuka
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May 20, 2022
simonbasle
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simonbasle
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As a follow-up to #3045, this commit introduces an ArchUnit rule to surface other cases where a Subscriber is a QueueSubscription but doesn't implement `onNext` (and thus can break ASYNC fusion). Three additional case have thus been surfaced, two of which cannot be fixed entirely. `doFinally`: in the `poll()` path there was no catching of `qs.poll()` exceptions BUT unfortunately there is no clean way to implement fused doFinally with thrown exceptions. For instance, assuming the following is fused: ``` .doFinally(sig -> signals.add("finally")) .doOnError(e -> signals.add("onError")) ``` then the `doFinally` handler is invoked BEFORE the doOnError (which is contrary to the documented order and the unfused order). This commit thus removes `Fuseable` trait from doFinally operators. `doAfterTerminate`: this is similar to the above situation, but fusion support needs not be entirely removed from `MonoPeekTerminal` if no "afterXxx" handler is defined. This commit thus forces fusion to be negotiated to `NONE` in case a `MonoPeekTerminal` has an `afterTerminateHandler`, and only in that case. `doOnError`: didn't catch polling exceptions either, so the `doOnError` handler from the above snippet was not even invoked. This commit fixes that case. Lastly, this commit fixes an out-of-order issue in `StepVerifier`'s handling of fusion: StepVerifierBuilder must cancel the upstream AFTER having propagated onError in ASYNC mode, otherwise it may hang.
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This commit fixes the DoOnEachFuseableSubscriber to interpret any
upstream onNext as a fusion trigger in ASYNC mode (onNext(null)).
Furthermore, this commit fixes the Operators.MonoSubscriber handling of
FUSED case. Since that abstract operator only supports ASYNC fusion,
the FUSED_* states are renamed FUSED_ASYNC_*. In the drain loop, even in
FUSED case the operator emits t downstream where it should emit null
technically (again, because FUSED == ASYNC). This error is also fixed.
Fixes #3044.