always store the filter subject

This avoids a situation where a consumer asks for
ORDERS.new today on a stream of ORDERS.new but later
someone makes the same stream ORDERS.* and the new
consumer would then get messages for other purposes
as well

Signed-off-by: R.I.Pienaar <rip@devco.net>

server/consumer.go

@@ -291,19 +291,7 @@ func (mset *stream) addConsumerWithAssignment(config *ConsumerConfig, oname stri
 
 	// Make sure any partition subject is also a literal.
 	if config.FilterSubject != _EMPTY_ {
-		var checkSubject bool
-
-		mset.mu.RLock()
-		// If this is a direct match for the streams only subject clear the filter.
-		if len(mset.cfg.Subjects) == 1 && mset.cfg.Subjects[0] == config.FilterSubject {
-			config.FilterSubject = _EMPTY_
-		} else {
-			checkSubject = true
-		}
-		mset.mu.RUnlock()
-
-		// Make sure this is a valid partition of the interest subjects.
-		if checkSubject && !mset.validSubject(config.FilterSubject) {
+		if !mset.validSubject(config.FilterSubject) {
 			return nil, fmt.Errorf("consumer filter subject is not a valid subset of the interest subjects")
 		}
 	}

server/jetstream_test.go

@@ -9283,9 +9283,9 @@ func TestJetStreamAckExplicitMsgRemoval(t *testing.T) {
 }
 
 // This test is in support fo clients that want to match on subject, they
-// can set the filter subject always and if the stream only has one subject
-// and they match the filter is cleared automatically. This eliminates us
-// needing to know if a subject is a subset of a stream when looking it up.
+// can set the filter subject always. We always store the subject so that
+// should the stream later be edited to expand into more subjects the consumer
+// still gets what was actually requested
 func TestJetStreamConsumerFilterSubject(t *testing.T) {
 	s := RunBasicJetStreamServer()
 	defer s.Shutdown()
@@ -9310,8 +9310,8 @@ func TestJetStreamConsumerFilterSubject(t *testing.T) {
 	}
 	defer o.delete()
 
-	if o.info().Config.FilterSubject != "" {
-		t.Fatalf("Expected the filter to be cleared")
+	if o.info().Config.FilterSubject != "foo" {
+		t.Fatalf("Expected the filter to be stored")
 	}
 
 	// Now use the original cfg with updated delivery subject and make sure that works ok.