feat: Reimplement MapConcat operator without statefulMapConcat. #902
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| /* | ||
| * Licensed to the Apache Software Foundation (ASF) under one or more | ||
| * contributor license agreements. See the NOTICE file distributed with | ||
| * this work for additional information regarding copyright ownership. | ||
| * The ASF licenses this file to You under the Apache License, Version 2.0 | ||
| * (the "License"); you may not use this file except in compliance with | ||
| * the License. You may obtain a copy of the License at | ||
| * | ||
| * http://www.apache.org/licenses/LICENSE-2.0 | ||
| * | ||
| * Unless required by applicable law or agreed to in writing, software | ||
| * distributed under the License is distributed on an "AS IS" BASIS, | ||
| * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. | ||
| * See the License for the specific language governing permissions and | ||
| * limitations under the License. | ||
| */ | ||
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| package org.apache.pekko.stream.impl.fusing | ||
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| import scala.util.control.Exception.Catcher | ||
| import scala.util.control.NonFatal | ||
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| import org.apache.pekko | ||
| import pekko.annotation.InternalApi | ||
| import pekko.stream.{ Attributes, FlowShape, Inlet, Outlet, Supervision } | ||
| import pekko.stream.ActorAttributes.SupervisionStrategy | ||
| import pekko.stream.Attributes.SourceLocation | ||
| import pekko.stream.Supervision.Decider | ||
| import pekko.stream.impl.Stages.DefaultAttributes | ||
| import pekko.stream.stage.{ GraphStage, GraphStageLogic, InHandler, OutHandler } | ||
| import pekko.util.ccompat._ | ||
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| /** | ||
| * INTERNAL API | ||
| */ | ||
| @InternalApi | ||
| @ccompatUsedUntil213 | ||
| private[pekko] final class MapConcat[In, Out](f: In => IterableOnce[Out]) | ||
| extends GraphStage[FlowShape[In, Out]] { | ||
| require(f != null, "f function should not be null") | ||
| private val in = Inlet[In]("MapConcat.in") | ||
| private val out = Outlet[Out]("MapConcat.out") | ||
| override val shape: FlowShape[In, Out] = FlowShape(in, out) | ||
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| override def initialAttributes: Attributes = DefaultAttributes.mapConcat and SourceLocation.forLambda(f) | ||
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| override def createLogic(inheritedAttributes: Attributes): GraphStageLogic = | ||
| new GraphStageLogic(shape) with InHandler with OutHandler { | ||
| private lazy val decider: Decider = inheritedAttributes.mandatoryAttribute[SupervisionStrategy].decider | ||
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| private var currentIterator: Iterator[Out] = _ | ||
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| private def hasNext = currentIterator != null && currentIterator.hasNext | ||
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| override def onPush(): Unit = | ||
| try { | ||
| currentIterator = f(grab(in)).iterator | ||
| tryPushAndPull() | ||
| } catch handleException | ||
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| private def tryPushAndPull(): Unit = | ||
| try { | ||
| if (hasNext) { | ||
| push(out, currentIterator.next()) | ||
| if (!hasNext && isClosed(in)) { | ||
| completeStage() | ||
| } | ||
| } else if (isClosed(in)) completeStage() | ||
| else pull(in) | ||
| } catch handleException | ||
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There was a problem hiding this comment. as both |
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| private def handleException: Catcher[Unit] = { | ||
| case NonFatal(ex) => | ||
| decider(ex) match { | ||
| case Supervision.Stop => failStage(ex) | ||
| case _ => | ||
| if (isClosed(in)) completeStage() | ||
| else if (!hasBeenPulled(in)) pull(in) | ||
| } | ||
| } | ||
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| override def onPull(): Unit = tryPushAndPull() | ||
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| override def onUpstreamFinish(): Unit = if (!hasNext) completeStage() | ||
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| setHandlers(in, out, this) | ||
| } | ||
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| override def toString: String = "MapConcat" | ||
| } | ||
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It seems to be defensive, is it nessnary check?
We should specify the parent of the function, like
f function of MapConcat should not be null?There was a problem hiding this comment.
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Yes，better than a materilixation error.
As the stack trace can show the detail, that's information can be ommited