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Add ZStream.onError #4097

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Merged
merged 1 commit into from
Aug 15, 2020
Merged

Add ZStream.onError #4097

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7 changes: 7 additions & 0 deletions streams-tests/shared/src/test/scala/zio/stream/ZStreamSpec.scala
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Original file line number Diff line number Diff line change
Expand Up @@ -2169,6 +2169,13 @@ object ZStreamSpec extends ZIOBaseSpec {
}
}
},
testM("onError") {
for {
flag <- Ref.make(false)
exit <- ZStream.fail("Boom").onError(_ => flag.set(true)).runDrain.run
called <- flag.get
} yield assert(called)(isTrue) && assert(exit)(fails(equalTo("Boom")))
} @@ zioTag(errors),
testM("orElse") {
val s1 = ZStream(1, 2, 3) ++ ZStream.fail("Boom")
val s2 = ZStream(4, 5, 6)
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8 changes: 8 additions & 0 deletions streams/shared/src/main/scala/zio/stream/ZStream.scala
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Expand Up @@ -2062,6 +2062,14 @@ abstract class ZStream[-R, +E, +O](val process: ZManaged[R, Nothing, ZIO[R, Opti
}
}

/**
* Runs the specified effect if this stream fails, providing the error to the effect if it exists.
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The corresponding method on ZIO guarantees the execution of cleanup even in the face of interruption, and also executes it uninterruptibly.

I don't think it's critical to replicate those same semantics here, but let's add a note on the scaladoc about this difference.

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Yeah I'm not sure if it's possible to provide the same semantics.
I added a note to the scaladoc.

*
* Note: Unlike [[ZIO.onError]], there is no guarantee that the provided effect will not be interrupted.
*/
final def onError[R1 <: R](cleanup: Cause[E] => URIO[R1, Any]): ZStream[R1, E, O] =
catchAllCause(cause => ZStream.fromEffect(cleanup(cause) *> ZIO.halt(cause)))

/**
* Switches to the provided stream in case this one fails with a typed error.
*
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