FlowableScanSeed - prevent post-terminal events

ReactiveX · Dec 3, 2016 · 9918a4f · 9918a4f
1 parent 846afd3
commit 9918a4f
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diff --git a/src/main/java/io/reactivex/internal/operators/flowable/FlowableScanSeed.java b/src/main/java/io/reactivex/internal/operators/flowable/FlowableScanSeed.java
@@ -51,6 +51,8 @@ static final class ScanSeedSubscriber<T, R> extends SinglePostCompleteSubscriber
         private static final long serialVersionUID = -1776795561228106469L;
 
         final BiFunction<R, ? super T, R> accumulator;
+
+        boolean done = false;
 
         ScanSeedSubscriber(Subscriber<? super R> actual, BiFunction<R, ? super T, R> accumulator, R value) {
             super(actual);
@@ -80,12 +82,20 @@ public void onNext(T t) {
 
         @Override
         public void onError(Throwable t) {
+            if (done) {
+                return;
+            }
+            done = true;
             value = null;
             actual.onError(t);
         }
 
         @Override
         public void onComplete() {
+            if (done) {
+                return;
+            }
+            done = true;
             complete(value);
         }
     }

diff --git a/src/test/java/io/reactivex/flowable/FlowableScanTests.java b/src/test/java/io/reactivex/flowable/FlowableScanTests.java
@@ -14,9 +14,11 @@
 package io.reactivex.flowable;
 
 import java.util.HashMap;
+import java.util.concurrent.Callable;
 
 import org.junit.Test;
 
+import io.reactivex.Flowable;
 import io.reactivex.flowable.FlowableEventStream.Event;
 import io.reactivex.functions.*;
 
@@ -41,4 +43,66 @@ public void accept(HashMap<String, String> v) {
             }
         });
     }
+
+    @Test
+    public void testFlowableScanSeedDoesNotEmitErrorTwiceIfScanFunctionThrows() {
+        final RuntimeException e = new RuntimeException();
+        Burst.item(1).error(e).scan(0, new BiFunction<Integer, Integer, Integer>() {
+
+            @Override
+            public Integer apply(Integer n1, Integer n2) throws Exception {
+                throw e;
+            }})
+          .test()
+          .assertNoValues()
+          .assertError(e);
+    }
+
+    @Test
+    public void testFlowableScanSeedDoesNotEmitTerminalEventTwiceIfScanFunctionThrows() {
+        final RuntimeException e = new RuntimeException();
+        Burst.item(1).create().scan(0, new BiFunction<Integer, Integer, Integer>() {
+
+            @Override
+            public Integer apply(Integer n1, Integer n2) throws Exception {
+                throw e;
+            }})
+          .test()
+          .assertNoValues()
+          .assertError(e);
+    }
+
+    @Test
+    public void testFlowableScanSeedCompletesNormally() {
+        Flowable.just(1,2,3).scan(0, new BiFunction<Integer, Integer, Integer>() {
+
+            @Override
+            public Integer apply(Integer t1, Integer t2) throws Exception {
+                return t1 + t2;
+            }})
+          .test()
+          .assertValues(0, 1, 3, 6)
+          .assertComplete();
+    }
+
+    @Test
+    public void testFlowableScanSeedWhenScanSeedProviderThrows() {
+        final RuntimeException e = new RuntimeException();
+        Flowable.just(1,2,3).scanWith(new Callable<Integer>() {
+            @Override
+            public Integer call() throws Exception {
+                throw e;
+            }
+        },
+            new BiFunction<Integer, Integer, Integer>() {
+
+                @Override
+                public Integer apply(Integer t1, Integer t2) throws Exception {
+                    return t1 + t2;
+                }
+           })
+          .test()
+          .assertError(e)
+          .assertNoValues();
+    }
 }