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8328316: Finisher cannot emit if stream is sequential and integrator …
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…returned false

Reviewed-by: psandoz
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Viktor Klang committed Mar 21, 2024
1 parent ba05c6d commit ab28045
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Showing 2 changed files with 71 additions and 5 deletions.
11 changes: 6 additions & 5 deletions src/java.base/share/classes/java/util/stream/GathererOp.java
Original file line number Diff line number Diff line change
@@ -1,5 +1,5 @@
/*
* Copyright (c) 2023, Oracle and/or its affiliates. All rights reserved.
* Copyright (c) 2023, 2024, Oracle and/or its affiliates. All rights reserved.
* DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
*
* This code is free software; you can redistribute it and/or modify it
Expand Down Expand Up @@ -142,6 +142,7 @@ static final class GatherSink<T, A, R> implements Sink<T>, Gatherer.Downstream<R
private final Integrator<A, T, R> integrator; // Optimization: reuse
private A state;
private boolean proceed = true;
private boolean downstreamProceed = true;

GatherSink(Gatherer<T, A, R> gatherer, Sink<R> sink) {
this.gatherer = gatherer;
Expand Down Expand Up @@ -173,12 +174,12 @@ public void accept(T t) {

@Override
public boolean cancellationRequested() {
return cancellationRequested(proceed);
return cancellationRequested(proceed && downstreamProceed);
}

private boolean cancellationRequested(boolean knownProceed) {
// Highly performance sensitive
return !(knownProceed && (!sink.cancellationRequested() || (proceed = false)));
return !(knownProceed && (!sink.cancellationRequested() || (downstreamProceed = false)));
}

@Override
Expand All @@ -194,12 +195,12 @@ public void end() {

@Override
public boolean isRejecting() {
return !proceed;
return !downstreamProceed;
}

@Override
public boolean push(R r) {
var p = proceed;
var p = downstreamProceed;
if (p)
sink.accept(r);
return !cancellationRequested(p);
Expand Down
65 changes: 65 additions & 0 deletions test/jdk/java/util/stream/GathererShortCircuitTest.java
Original file line number Diff line number Diff line change
@@ -0,0 +1,65 @@
/*
* Copyright (c) 2024, Oracle and/or its affiliates. All rights reserved.
* DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
*
* This code is free software; you can redistribute it and/or modify it
* under the terms of the GNU General Public License version 2 only, as
* published by the Free Software Foundation.
*
* This code is distributed in the hope that it will be useful, but WITHOUT
* ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
* FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License
* version 2 for more details (a copy is included in the LICENSE file that
* accompanied this code).
*
* You should have received a copy of the GNU General Public License version
* 2 along with this work; if not, write to the Free Software Foundation,
* Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.
*
* Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA
* or visit www.oracle.com if you need additional information or have any
* questions.
*/
import java.util.List;
import java.util.stream.Collectors;
import java.util.stream.Gatherer;

import org.junit.jupiter.api.Test;
import static org.junit.jupiter.api.Assertions.*;
import static org.junit.jupiter.api.Assumptions.*;

/**
* @test
* @bug 8328316
* @summary Testing Gatherer behavior under short circuiting
* @enablePreview
* @run junit GathererShortCircuitTest
*/

public class GathererShortCircuitTest {
@Test
public void mustBeAbleToPushFromFinisher() {
Integer expected = 8328316;
List<Integer> source = List.of(1,2,3,4,5);

Gatherer<Integer, ?, Integer> pushOneInFinisher =
Gatherer.of(
(_, element, downstream) -> false,
(_, downstream) -> downstream.push(expected)
);

var usingCollect =
source.stream().gather(pushOneInFinisher).collect(Collectors.toList());
var usingBuiltin =
source.stream().gather(pushOneInFinisher).toList();
var usingCollectPar =
source.stream().parallel().gather(pushOneInFinisher).collect(Collectors.toList());
var usingBuiltinPar =
source.stream().parallel().gather(pushOneInFinisher).toList();

assertEquals(List.of(expected), usingCollect);
assertEquals(List.of(expected), usingBuiltin);
assertEquals(List.of(expected), usingCollectPar);
assertEquals(List.of(expected), usingBuiltinPar);
}
}

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