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Pull: turn flatMapOutput into an extension method. #3016

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merged 1 commit into from
Oct 16, 2022
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Pull: turn flatMapOutput into an extension method. #3016

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22 changes: 14 additions & 8 deletions core/shared/src/main/scala/fs2/Pull.scala
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Original file line number Diff line number Diff line change
Expand Up @@ -321,6 +321,16 @@ object Pull extends PullLowPriority {
* Use `p.void.stream` to explicitly ignore the result of a pull.
*/
def streamNoScope: Stream[F, O] = new Stream(self)

private[fs2] def flatMapOutput[F2[x] >: F[x], O2](
f: O => Pull[F2, O2, Unit]
): Pull[F2, O2, Unit] =
self match {
case a: AlgEffect[F, Unit] => a
case r: Terminal[_] => r
case _ => FlatMapOutput(self, f)
}

}

private[this] val unit: Terminal[Unit] = Succeeded(())
Expand Down Expand Up @@ -1029,7 +1039,7 @@ object Pull extends PullLowPriority {
else {
def go(idx: Int): Pull[G, X, Unit] =
if (idx == chunk.size)
flatMapOutput[G, G, Y, X](tail, fun)
tail.flatMapOutput(fun)
else {
try {
var j = idx
Expand All @@ -1046,8 +1056,7 @@ object Pull extends PullLowPriority {
case Succeeded(_) => go(j + 1)
case Fail(err) => Fail(err)
case interruption @ Interrupted(_, _) =>
val ib = interruptBoundary(tail, interruption)
flatMapOutput[G, G, Y, X](ib, fun)
interruptBoundary(tail, interruption).flatMapOutput(fun)
}
} catch { case NonFatal(e) => Fail(e) }
}
Expand Down Expand Up @@ -1288,15 +1297,12 @@ object Pull extends PullLowPriority {
go(initScope, None, initFk, new OuterRun(init), stream)
}

@deprecated("use the extension method", "3.4.0")
private[fs2] def flatMapOutput[F[_], F2[x] >: F[x], O, O2](
p: Pull[F, O, Unit],
f: O => Pull[F2, O2, Unit]
): Pull[F2, O2, Unit] =
p match {
case a: AlgEffect[F, Unit] => a
case r: Terminal[_] => r
case _ => FlatMapOutput(p, f)
}
p.flatMapOutput(f)

private[fs2] def translate[F[_], G[_], O](
stream: Pull[F, O, Unit],
Expand Down
14 changes: 7 additions & 7 deletions core/shared/src/main/scala/fs2/Stream.scala
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Expand Up @@ -962,6 +962,8 @@ final class Stream[+F[_], +O] private[fs2] (private[fs2] val underlying: Pull[F,
queue: Queue[F2, Option[Chunk[O2]]]
): Stream[F2, Nothing] = enqueueNoneTerminatedChunks(queue: QueueSink[F2, Option[Chunk[O2]]])

import Pull.StreamPullOps
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Why is the import necessary, is it not in implicit scope automatically?

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@diesalbla diesalbla Oct 16, 2022 •
edited
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Failed to compile in Scala 3 without it. It could be that Scala 3 has narrowed that scope.


/** Alias for `flatMap(o => Stream.eval(f(o)))`.
*
* @example {{{
Expand All @@ -975,8 +977,8 @@ final class Stream[+F[_], +O] private[fs2] (private[fs2] val underlying: Pull[F,
* is available, however, with caveats.
*/
def evalMap[F2[x] >: F[x], O2](f: O => F2[O2]): Stream[F2, O2] = {
def evalOut(o: O): Pull[F2, O2, Unit] = Pull.eval(f(o)).flatMap(Pull.output1)
Pull.flatMapOutput[F, F2, O, O2](underlying, evalOut).streamNoScope
def evalOut(o: O) = Pull.eval(f(o)).flatMap(Pull.output1)
underlying.flatMapOutput(evalOut).streamNoScope
}

/** Like `evalMap`, but operates on chunks for performance. This means this operator
Expand Down Expand Up @@ -1194,7 +1196,7 @@ final class Stream[+F[_], +O] private[fs2] (private[fs2] val underlying: Pull[F,
def flatMap[F2[x] >: F[x], O2](
f: O => Stream[F2, O2]
)(implicit ev: NotGiven[O <:< Nothing]): Stream[F2, O2] =
new Stream(Pull.flatMapOutput[F, F2, O, O2](underlying, (o: O) => f(o).underlying))
underlying.flatMapOutput((o: O) => f(o).underlying).streamNoScope

/** Alias for `flatMap(_ => s2)`. */
def >>[F2[x] >: F[x], O2](
Expand Down Expand Up @@ -1285,10 +1287,8 @@ final class Stream[+F[_], +O] private[fs2] (private[fs2] val underlying: Pull[F,
* res0: Unit = ()
* }}}
*/
def foreach[F2[x] >: F[x]](f: O => F2[Unit]): Stream[F2, Nothing] = {
def exec(o: O): Pull[F2, Nothing, Unit] = Pull.eval(f(o))
Pull.flatMapOutput[F, F2, O, Nothing](underlying, exec).streamNoScope
}
def foreach[F2[x] >: F[x]](f: O => F2[Unit]): Stream[F2, Nothing] =
underlying.flatMapOutput(o => Pull.eval(f(o))).streamNoScope

/** Partitions the input into a stream of chunks according to a discriminator function.
*
Expand Down