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Sink.take should also emit at end of chunk. #4342

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Merged
merged 4 commits into from
Oct 29, 2020
Merged

Sink.take should also emit at end of chunk. #4342

merged 4 commits into from
Oct 29, 2020

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@quelgar
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@quelgar quelgar commented Oct 21, 2020 •
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Currently if Sink.take(n) collects the nth element at the end of a chunk, it will not emit its output until the stream ends or another element is received. In this situation it should just emit immediately, with an empty left-over.

It's a one character fix, but I lack the knowledge and/or imagination to construct a good test for it. I've been manually testing like this:

val s1 = Stream(1, 2) ++ Stream(3, 4)
runtime.unsafeRun(s1.run(Sink.take(2))) // emits Chunk(1, 2) immediately

val s2 = Stream(1, 2) ++ Stream(3, 4).mapChunksM(c => ZIO.sleep(15.seconds).as(c))
runtime.unsafeRun(s2.run(Sink.take(2)))  // master takes 15 seconds to emit Chunk(1, 2)

Any suggestions on how to write a good test for this? Never mind, I had a brainwave that Stream.never is what I needed.

@quelgar
Sink.take should also emit at end of chunk.
01d515c 
If there's exactly enough data for Sink.take, it should emit
immediately with empty leftover.
@quelgar quelgar requested a review from iravid as a code owner October 21, 2020 01:30
@narma
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narma commented Oct 26, 2020 •
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Good catch!

Couple of thoughts:
idx is not correct naming there because actually, this value means how much left we want elements left to grab in. Because how we get it: n - take.length, where take is an accumulator. And this, I think, was leads to the issue, because idx always should be less than length.

My proposal here is rename idx to remain or something like that.
Also, I think Stream.die is a more convenient way to test behavior like this instead of Stream.never, because of in bad case it will be faster.

@quelgar
PR comments.
bb6a272 
Test using Sink.die.
@quelgar
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quelgar commented Oct 27, 2020

@narma yes, Stream.die is better, done 👍

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narma commented Oct 29, 2020

@adamgfraser @iravid Guys, any suggestions?

adamgfraser
adamgfraser approved these changes Oct 29, 2020
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Good catch!

@adamgfraser adamgfraser merged commit bfc2a78 into zio:master Oct 29, 2020
@quelgar quelgar deleted the sink-take-emit-end-of-chunk branch November 12, 2020 12:16
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@iravid iravid Awaiting requested review from iravid

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@adamgfraser adamgfraser adamgfraser approved these changes

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3 participants

@quelgar @narma @adamgfraser