From 3e6aea346d7592b79a4516a14f73819f4f75b135 Mon Sep 17 00:00:00 2001
From: Rossen Stoyanchev <rstoyanchev@pivotal.io>
Date: Tue, 16 Jun 2020 07:36:41 +0100
Subject: [PATCH] Align MonoCollect with MonoList

This change aligns the implementation of MonoCollect to be comparable
to MonoList. Effectively they're the same, a MonoList is but a
MonoCollect with an ArrayList as the container.

Fix #2186
---
 .../reactor/core/publisher/MonoCollect.java   | 95 ++++++++++++-------
 .../core/publisher/MonoCollectList.java       |  8 +-
 .../core/publisher/MonoCollectTest.java       |  1 -
 3 files changed, 65 insertions(+), 39 deletions(-)

diff --git a/reactor-core/src/main/java/reactor/core/publisher/MonoCollect.java b/reactor-core/src/main/java/reactor/core/publisher/MonoCollect.java
index b66d7d8380..f8439f1cc2 100644
--- a/reactor-core/src/main/java/reactor/core/publisher/MonoCollect.java
+++ b/reactor-core/src/main/java/reactor/core/publisher/MonoCollect.java
@@ -72,6 +72,8 @@ static final class CollectSubscriber<T, R> extends Operators.MonoSubscriber<T, R
 
 		final BiConsumer<? super R, ? super T> action;
 
+		R container;
+
 		Subscription s;
 
 		boolean done;
@@ -81,35 +83,17 @@ static final class CollectSubscriber<T, R> extends Operators.MonoSubscriber<T, R
 				R container) {
 			super(actual);
 			this.action = action;
-			this.value = container;
+			this.container = container;
 		}
 
 		@Override
 		@Nullable
 		public Object scanUnsafe(Attr key) {
-			if (key == Attr.TERMINATED) return done;
 			if (key == Attr.PARENT) return s;
-
+			if (key == Attr.TERMINATED) return done;
 			return super.scanUnsafe(key);
 		}
 
-		@Override
-		public void cancel() {
-			super.cancel();
-			s.cancel();
-		}
-
-		@Override
-		protected void discard(R v) {
-			if (v instanceof Collection) {
-				Collection<?> c = (Collection<?>) v;
-				Operators.onDiscardMultiple(c, actual.currentContext());
-			}
-			else {
-				super.discard(v);
-			}
-		}
-
 		@Override
 		public void onSubscribe(Subscription s) {
 			if (Operators.validate(this.s, s)) {
@@ -127,15 +111,22 @@ public void onNext(T t) {
 				Operators.onNextDropped(t, actual.currentContext());
 				return;
 			}
-
-			try {
-				action.accept(value, t);
-			}
-			catch (Throwable e) {
-				Context ctx = actual.currentContext();
-				Operators.onDiscard(t, ctx);
-				onError(Operators.onOperatorError(this, e, t, ctx));
+			R c;
+			synchronized (this) {
+				c = container;
+				if (c != null) {
+					try {
+						action.accept(c, t);
+					}
+					catch (Throwable e) {
+						Context ctx = actual.currentContext();
+						Operators.onDiscard(t, ctx);
+						onError(Operators.onOperatorError(this, e, t, ctx));
+					}
+					return;
+				}
 			}
+			Operators.onDiscard(t, actual.currentContext());
 		}
 
 		@Override
@@ -145,9 +136,12 @@ public void onError(Throwable t) {
 				return;
 			}
 			done = true;
-			R v = value;
-			discard(v);
-			value = null;
+			R c;
+			synchronized (this) {
+				c = container;
+				container = null;
+			}
+			discard(c);
 			actual.onError(t);
 		}
 
@@ -157,13 +151,46 @@ public void onComplete() {
 				return;
 			}
 			done = true;
-			complete(value);
+			R c;
+			synchronized (this) {
+				c = container;
+				container = null;
+			}
+			if (c != null) {
+				complete(c);
+			}
 		}
 
 		@Override
-		public void setValue(R value) {
-			// value is constant
+		protected void discard(R v) {
+			if (v instanceof Collection) {
+				Collection<?> c = (Collection<?>) v;
+				Operators.onDiscardMultiple(c, actual.currentContext());
+			}
+			else {
+				super.discard(v);
+			}
 		}
 
+		@Override
+		public void cancel() {
+			int state;
+			R c;
+			synchronized (this) {
+				state = STATE.getAndSet(this, CANCELLED);
+				if (state <= HAS_REQUEST_NO_VALUE) {
+					c = container;
+					value = null;
+					container = null;
+				}
+				else {
+					c = null;
+				}
+			}
+			if (c != null) {
+				s.cancel();
+				discard(c);
+			}
+		}
 	}
 }
diff --git a/reactor-core/src/main/java/reactor/core/publisher/MonoCollectList.java b/reactor-core/src/main/java/reactor/core/publisher/MonoCollectList.java
index b02b253cff..70dff4a8ef 100644
--- a/reactor-core/src/main/java/reactor/core/publisher/MonoCollectList.java
+++ b/reactor-core/src/main/java/reactor/core/publisher/MonoCollectList.java
@@ -42,10 +42,10 @@ public void subscribe(CoreSubscriber<? super List<T>> actual) {
 
 	static final class MonoCollectListSubscriber<T> extends Operators.MonoSubscriber<T, List<T>> {
 
-		Subscription s;
-
 		List<T> list;
 
+		Subscription s;
+
 		boolean done;
 
 		MonoCollectListSubscriber(CoreSubscriber<? super List<T>> actual) {
@@ -92,7 +92,7 @@ public void onNext(T t) {
 
 		@Override
 		public void onError(Throwable t) {
-			if(done) {
+			if (done) {
 				Operators.onErrorDropped(t, actual.currentContext());
 				return;
 			}
@@ -102,7 +102,7 @@ public void onError(Throwable t) {
 				l = list;
 				list = null;
 			}
-			Operators.onDiscardMultiple(l, actual.currentContext());
+			discard(l);
 			actual.onError(t);
 		}
 
diff --git a/reactor-core/src/test/java/reactor/core/publisher/MonoCollectTest.java b/reactor-core/src/test/java/reactor/core/publisher/MonoCollectTest.java
index 2327a44279..4bd6698b50 100644
--- a/reactor-core/src/test/java/reactor/core/publisher/MonoCollectTest.java
+++ b/reactor-core/src/test/java/reactor/core/publisher/MonoCollectTest.java
@@ -20,7 +20,6 @@
 import java.util.ArrayList;
 import java.util.Arrays;
 import java.util.List;
-import java.util.concurrent.atomic.AtomicBoolean;
 import java.util.concurrent.atomic.AtomicInteger;
 
 import org.junit.Assert;