Fix streaming APIs' Err method closing stream (#2882)

Fixes calling the Err method on SDK's Amazon Kinesis's SubscribeToShared
and Amazon S3's SelectObjectContent response EventStream members closing
the stream. This would cause unexpected read errors, or early
termination of the streams. Only the Close method of the streaming
members will close the streams.

Improved generated unit and integration tests for streaming API
operations.

Related to #2769

CHANGELOG_PENDING.md

@@ -3,3 +3,7 @@
 ### SDK Enhancements
 
 ### SDK Bugs
+* `service/s3`,`service/kinesis`: Fix streaming APIs' Err method closing stream ([#2882](https://github.com/aws/aws-sdk-go/pull/2882))
+  * Fixes calling the Err method on SDK's Amazon Kinesis's SubscribeToShared and Amazon S3's SelectObjectContent response EventStream members closing the stream. This would cause unexpected read errors, or early termination of the streams. Only the Close method of the streaming members will close the streams.
+  * Related to [#2769](https://github.com/aws/aws-sdk-go/issues/2769)
+

private/model/api/eventstream.go

@@ -208,7 +208,7 @@ func setupEventStream(topShape *Shape) *EventStream {
 			eventRef.Shape.EventFor = append(eventRef.Shape.EventFor, eventStream)
 
 			// Exceptions and events are two different lists to allow the SDK
-			// to easly generate code with the two handled differently.
+			// to easily generate code with the two handled differently.
 			event := &Event{
 				Name:  eventRefName,
 				Shape: eventRef.Shape,
@@ -335,6 +335,8 @@ func (es *{{ $.ShapeName }}) Close() (err error) {
 		es.Writer.Close()
 	{{ end -}}
 
+	es.StreamCloser.Close()
+
 	return es.Err()
 }
 
@@ -353,8 +355,6 @@ func (es *{{ $.ShapeName }}) Err() error {
 		}
 	{{ end -}}
 
-	es.StreamCloser.Close()
-
 	return nil
 }
 
@@ -974,6 +974,18 @@ func (c *loopReader) Read(p []byte) (int, error) {
 			t.Fatalf("expect no error got, %v", err)
 		}
 
+		{{ if gt (len $.Inbound.Events) 0 -}}
+			// Assert calling Err before close does not close the stream.
+			resp.{{ $esMemberName }}.Err()
+			select {
+			case _, ok := <-resp.{{ $esMemberName }}.Events():
+				if !ok {
+					t.Fatalf("expect stream not to be closed, but was")
+				}
+			default:
+			}
+		{{- end }}
+
 		resp.{{ $esMemberName }}.Close()
 		<-resp.{{ $esMemberName }}.Events()