FlowableWithLatestFrom forgets request

[matgabriel]

The following scenario did not work with FlowableWithLatestFrom:
Flowable<?> result = source.combineWithLatest(other, someCombiner)

• client subscribe to the result stream
• source stream emits
• other stream emits
• source stream emits

expected result: result stream emits the combined event
actual result: result stream does not emit anything

[akarnokd]

Nice find and I'm a bit baffled as FlowableWithLatestFromMany does not have this flaw...

[akarnokd]

Please don't change existing tests but add new ones instead.

[matgabriel]

ok, I have added a test, but I still had to modify testBackpressure because it was relying on the fact that the source would not get more request if the other stream does not emit data.

[codecov]

Codecov Report

Merging #5494 into 2.x will decrease coverage by 0.07%.
The diff coverage is 100%.

@@             Coverage Diff              @@
##                2.x    #5494      +/-   ##
============================================
- Coverage     96.11%   96.03%   -0.08%     
+ Complexity     5798     5797       -1     
============================================
  Files           631      631              
  Lines         41297    41299       +2     
  Branches       5743     5743              
============================================
- Hits          39692    39663      -29     
- Misses          632      654      +22     
- Partials        973      982       +9

Impacted Files	Coverage Δ	Complexity Δ
...nal/operators/flowable/FlowableWithLatestFrom.java	100% <100%> (ø)	2 <0> (ø)	⬇️
...in/java/io/reactivex/subjects/BehaviorSubject.java	84.89% <0%> (-6.78%)	56% <0%> (ø)
...reactivex/internal/operators/maybe/MaybeUsing.java	93.93% <0%> (-6.07%)	4% <0%> (ø)
.../operators/observable/ObservableFlatMapSingle.java	88.8% <0%> (-5.98%)	2% <0%> (ø)
...ernal/operators/flowable/FlowableFlatMapMaybe.java	90.33% <0%> (-5.8%)	2% <0%> (ø)
...vex/internal/operators/single/SingleTakeUntil.java	86.88% <0%> (-4.92%)	2% <0%> (ø)
...nternal/operators/parallel/ParallelReduceFull.java	91.17% <0%> (-3.93%)	2% <0%> (ø)
...tivex/internal/observers/FutureSingleObserver.java	94.33% <0%> (-3.78%)	24% <0%> (-1%)
...internal/operators/completable/CompletableAmb.java	94.91% <0%> (-3.39%)	10% <0%> (-1%)
...ex/internal/operators/maybe/MaybeTimeoutMaybe.java	95.58% <0%> (-2.95%)	2% <0%> (ø)
... and 42 more

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