Introduce Flow.any, Flow.all, Flow.none #4249
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I took inspiration from other tests, which seem to use |
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expect and finish are used to describe when exactly which code is run. If there are 100 steps, the chain of calls must be expect(1), expect(2), expect(3) ... finish(100) and nothing else. If the test is broken and expect(5) runs before expect(4) did, the test fails.
This isn't useful for the tests you've already written. It could potentially be useful for tests that are missing, those that show short-circuiting behavior: flow { emit(1); fail("unreached") }.any { it == 1 } should finish without an error. Or maybe not.
| * This operation is *terminal*. | ||
| * | ||
| * @see Iterable.any | ||
| * @see Sequence.any |
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Flow.all also seems relevant.
| @@ -164,3 +164,46 @@ public fun <T> Flow<T>.chunked(size: Int): Flow<List<T>> { | |||
| result?.let { emit(it) } | |||
| } | |||
| } | |||
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| /** | |||
| * Returns `true` if at least one element matches the given [predicate]. | |||
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Another important property is that it immediately stops collecting the flow. See https://kotlinlang.org/api/kotlinx.coroutines/kotlinx-coroutines-core/kotlinx.coroutines.flow/first.html
Also, this only returns false if the flow completes without emitting a value that matches the predicate. I'm not sure if it's worth spelling out (this does seem obvious).
Finally, please include a simple usage sample in the documentation for every new function.
| */ | ||
| @ExperimentalCoroutinesApi | ||
| public suspend fun <T> Flow<T>.all(predicate: suspend (T) -> Boolean): Boolean = | ||
| count { !predicate(it) } == 0 |
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This implementation will hang in this scenario: flow { while (true) { emit(5) } }.all { it == 4 }.
| */ | ||
| @ExperimentalCoroutinesApi | ||
| public suspend fun <T> Flow<T>.none(predicate: suspend (T) -> Boolean): Boolean = | ||
| count { predicate(it) } == 0 |
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Likewise, it will hang for flow { while (true) { emit(5) } }.none { it == 5 }. Please include these scenarios (and a similar one for any) as tests.
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@CLOVIS-AI would you like to continue this PR or should we handle it from here? |
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I would love to, but sadly my schedule doesn't allow me too… Feel free to make the changes you want if I'm too slow :) |
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Closed in favor of #4304 |
As discussed in #4212.
This is my first proper contribution to Coroutines, so please be nice :)
At this stage, my goals are:
• Optimal API surface
• Correctness
I have not made any attempts to improve performance. In particular, I wouldn't be surprised if
anycould be improved. I believeallandnoneare optimal.