!str,htc replace and remove OneBoundedInterpreter

main work by @drewhk with contributions from @2m and @rkuhn

This work uncovered many well-hidden bugs in existing Stages, in
particular StatefulStage. These were hidden by the behavior of
OneBoundedInterpreter that normally behaves more orderly than it
guarantees in general, especially with respect to the timeliness of
delivery of upstream termination signals; the bugs were then that
internal state was not flushed when onComplete arrived “too early”.

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

@@ -27,9 +27,15 @@ class RecipeByteStrings extends RecipeSpec {
 
         override def onPull(ctx: Context[ByteString]): SyncDirective = emitChunkOrPull(ctx)
 
+        override def onUpstreamFinish(ctx: Context[ByteString]): TerminationDirective =
+          if (buffer.nonEmpty) ctx.absorbTermination()
+          else ctx.finish()
+
         private def emitChunkOrPull(ctx: Context[ByteString]): SyncDirective = {
-          if (buffer.isEmpty) ctx.pull()
-          else {
+          if (buffer.isEmpty) {
+            if (ctx.isFinishing) ctx.finish()
+            else ctx.pull()
+          } else {
             val (emit, nextBuffer) = buffer.splitAt(chunkSize)
             buffer = nextBuffer
             ctx.push(emit)

akka-docs-dev/rst/scala/code/docs/stream/cookbook/RecipeKeepAlive.scala

@@ -41,6 +41,8 @@ class RecipeKeepAlive extends RecipeSpec {
 
       val subscription = sub.expectSubscription()
 
+      // FIXME RK: remove (because I think this cannot deterministically be tested and it might also not do what it should anymore)
+
       tickPub.sendNext(())
 
       // pending data will overcome the keepalive

akka-docs-dev/rst/scala/code/docs/stream/cookbook/RecipeMissedTicks.scala

@@ -2,8 +2,9 @@ package docs.stream.cookbook
 
 import akka.stream.scaladsl._
 import akka.stream.testkit._
-
 import scala.concurrent.duration._
+import akka.testkit.TestLatch
+import scala.concurrent.Await
 
 class RecipeMissedTicks extends RecipeSpec {
 
@@ -22,8 +23,12 @@ class RecipeMissedTicks extends RecipeSpec {
         Flow[Tick].conflate(seed = (_) => 0)(
           (missedTicks, tick) => missedTicks + 1)
       //#missed-ticks
+      val latch = TestLatch(3)
+      val realMissedTicks: Flow[Tick, Int, Unit] =
+        Flow[Tick].conflate(seed = (_) => 0)(
+          (missedTicks, tick) => { latch.countDown(); missedTicks + 1 })
 
-      tickStream.via(missedTicks).to(sink).run()
+      tickStream.via(realMissedTicks).to(sink).run()
 
       pub.sendNext(())
       pub.sendNext(())
@@ -31,6 +36,8 @@ class RecipeMissedTicks extends RecipeSpec {
       pub.sendNext(())
 
       val subscription = sub.expectSubscription()
+      Await.ready(latch, 1.second)
+
       subscription.request(1)
       sub.expectNext(3)
 

akka-docs-dev/rst/scala/code/docs/stream/cookbook/RecipeSimpleDrop.scala

@@ -2,8 +2,9 @@ package docs.stream.cookbook
 
 import akka.stream.scaladsl.{ Flow, Sink, Source }
 import akka.stream.testkit._
-
 import scala.concurrent.duration._
+import akka.testkit.TestLatch
+import scala.concurrent.Await
 
 class RecipeSimpleDrop extends RecipeSpec {
 
@@ -15,13 +16,16 @@ class RecipeSimpleDrop extends RecipeSpec {
       val droppyStream: Flow[Message, Message, Unit] =
         Flow[Message].conflate(seed = identity)((lastMessage, newMessage) => newMessage)
       //#simple-drop
+      val latch = TestLatch(2)
+      val realDroppyStream =
+        Flow[Message].conflate(seed = identity)((lastMessage, newMessage) => { latch.countDown(); newMessage })
 
       val pub = TestPublisher.probe[Message]()
       val sub = TestSubscriber.manualProbe[Message]()
       val messageSource = Source(pub)
       val sink = Sink(sub)
 
-      messageSource.via(droppyStream).to(sink).run()
+      messageSource.via(realDroppyStream).to(sink).run()
 
       val subscription = sub.expectSubscription()
       sub.expectNoMsg(100.millis)
@@ -30,6 +34,8 @@ class RecipeSimpleDrop extends RecipeSpec {
       pub.sendNext("2")
       pub.sendNext("3")
 
+      Await.ready(latch, 1.second)
+
       subscription.request(1)
       sub.expectNext("3")