Fixed bug in Chunker, exposed by interpreter changes

akka-docs/rst/java/code/docs/stream/javadsl/cookbook/RecipeByteStrings.java

@@ -100,8 +100,15 @@ public class RecipeByteStrings extends RecipeTest {
                 @Override
                 public void onUpstreamFinish() throws Exception {
                   if (buffer.isEmpty()) completeStage();
-                  // elements left in buffer, keep accepting downstream pulls
+                  else {
-                  // and push from buffer until buffer is emitted
+                    // There are elements left in buffer, so
+                    // we keep accepting downstream pulls and push from buffer until emptied.
+                    //
+                    // It might be though, that the upstream finished while it was pulled, in which
+                    // case we will not get an onPull from the downstream, because we already had one.
+                    // In that case we need to emit from the buffer.
+                    if (isAvailable(out)) emitChunk();
+                  }
                 }
               });
             }

akka-docs/rst/scala/code/docs/stream/cookbook/RecipeByteStrings.scala

@@ -42,8 +42,15 @@ class RecipeByteStrings extends RecipeSpec {
 
             override def onUpstreamFinish(): Unit = {
               if (buffer.isEmpty) completeStage()
-              // elements left in buffer, keep accepting downstream pulls
+              else {
-              // and push from buffer until buffer is emitted
+                // There are elements left in buffer, so
+                // we keep accepting downstream pulls and push from buffer until emptied.
+                //
+                // It might be though, that the upstream finished while it was pulled, in which
+                // case we will not get an onPull from the downstream, because we already had one.
+                // In that case we need to emit from the buffer.
+                if (isAvailable(out)) emitChunk()
+              }
             }
           })
 

project/MiMa.scala

@@ -903,7 +903,10 @@ object MiMa extends AutoPlugin {
         ProblemFilters.exclude[ReversedMissingMethodProblem]("akka.cluster.pubsub.protobuf.msg.DistributedPubSubMessages#StatusOrBuilder.hasReplyToStatus"),
 
         // #20543 GraphStage subtypes should not be private to akka
-        ProblemFilters.exclude[DirectAbstractMethodProblem]("akka.stream.ActorMaterializer.actorOf")
+        ProblemFilters.exclude[DirectAbstractMethodProblem]("akka.stream.ActorMaterializer.actorOf"),
+
+        // Interpreter internals change
+        ProblemFilters.exclude[IncompatibleResultTypeProblem]("akka.stream.stage.GraphStageLogic.portToConn")
       ),
       "2.4.9" -> Seq(
         // #20994 adding new decode method, since we're on JDK7+ now