Fix updating a non unique consumer on workqueue stream not returning an error (#4654)

This is a possible fix for #4653.

Changes made:
1. Added tests for creating and updating consumers on a work queue
stream with overlapping subjects.
2. Check for overlapping subjects before
[updating](a25af02c73/server/consumer.go (L770))
the consumer config.
3. Changed [`func (*stream).partitionUnique(partitions []string)
bool`](a25af02c73/server/stream.go (L5269))
to accept the consumer name being checked so we can skip it while
checking for overlapping subjects (Required for
[`FilterSubjects`](a25af02c73/server/consumer.go (L75))
updates), wasn't needed before because the checks were made on creation
only.

There's only 1 thing that I'm not sure about.

In the [current work queue stream conflict
checks](a25af02c73/server/consumer.go (L796)),
the consumer config `Direct` is being checked if `false`, should we also
make this check before the update?

Signed-off-by: Pierre Mdawar <pierre@mdawar.dev>

server/consumer.go

@@ -767,6 +767,13 @@ func (mset *stream) addConsumerWithAssignment(config *ConsumerConfig, oname stri
 			if action == ActionCreate && !reflect.DeepEqual(*config, eo.config()) {
 				return nil, NewJSConsumerAlreadyExistsError()
 			}
+			// Check for overlapping subjects.
+			if mset.cfg.Retention == WorkQueuePolicy {
+				subjects := gatherSubjectFilters(config.FilterSubject, config.FilterSubjects)
+				if !mset.partitionUnique(cName, subjects) {
+					return nil, NewJSConsumerWQConsumerNotUniqueError()
+				}
+			}
 			err := eo.updateConfig(config)
 			if err == nil {
 				return eo, nil
@@ -805,7 +812,7 @@ func (mset *stream) addConsumerWithAssignment(config *ConsumerConfig, oname stri
 			if len(subjects) == 0 {
 				mset.mu.Unlock()
 				return nil, NewJSConsumerWQMultipleUnfilteredError()
-			} else if !mset.partitionUnique(subjects) {
+			} else if !mset.partitionUnique(cName, subjects) {
 				// Prior to v2.9.7, on a stream with WorkQueue policy, the servers
 				// were not catching the error of having multiple consumers with
 				// overlapping filter subjects depending on the scope, for instance

server/jetstream_consumer_test.go

@@ -534,6 +534,81 @@ func TestJetStreamConsumerActions(t *testing.T) {
 	require_Error(t, err)
 }
 
+func TestJetStreamConsumerActionsOnWorkQueuePolicyStream(t *testing.T) {
+	s := RunBasicJetStreamServer(t)
+	defer s.Shutdown()
+
+	nc, _ := jsClientConnect(t, s)
+	defer nc.Close()
+	acc := s.GlobalAccount()
+
+	mset, err := acc.addStream(&StreamConfig{
+		Name:      "TEST",
+		Retention: WorkQueuePolicy,
+		Subjects:  []string{"one", "two", "three", "four", "five.>"},
+	})
+	require_NoError(t, err)
+
+	_, err = mset.addConsumerWithAction(&ConsumerConfig{
+		Durable:        "C1",
+		FilterSubjects: []string{"one", "two"},
+		AckPolicy:      AckExplicit,
+	}, ActionCreate)
+	require_NoError(t, err)
+
+	_, err = mset.addConsumerWithAction(&ConsumerConfig{
+		Durable:        "C2",
+		FilterSubjects: []string{"three", "four"},
+		AckPolicy:      AckExplicit,
+	}, ActionCreate)
+	require_NoError(t, err)
+
+	_, err = mset.addConsumerWithAction(&ConsumerConfig{
+		Durable:        "C3",
+		FilterSubjects: []string{"five.*"},
+		AckPolicy:      AckExplicit,
+	}, ActionCreate)
+	require_NoError(t, err)
+
+	// Updating a consumer by removing a previous subject filter.
+	_, err = mset.addConsumerWithAction(&ConsumerConfig{
+		Durable:        "C1",
+		FilterSubjects: []string{"one"}, // Remove a subject.
+		AckPolicy:      AckExplicit,
+	}, ActionUpdate)
+	require_NoError(t, err)
+
+	// Updating a consumer without overlapping subjects.
+	_, err = mset.addConsumerWithAction(&ConsumerConfig{
+		Durable:        "C2",
+		FilterSubjects: []string{"three", "four", "two"}, // Add previously removed subject.
+		AckPolicy:      AckExplicit,
+	}, ActionUpdate)
+	require_NoError(t, err)
+
+	// Creating a consumer with overlapping subjects should return an error.
+	_, err = mset.addConsumerWithAction(&ConsumerConfig{
+		Durable:        "C4",
+		FilterSubjects: []string{"one", "two", "three", "four"},
+		AckPolicy:      AckExplicit,
+	}, ActionCreate)
+	require_Error(t, err)
+	if !IsNatsErr(err, JSConsumerWQConsumerNotUniqueErr) {
+		t.Errorf("want error %q, got %q", ApiErrors[JSConsumerWQConsumerNotUniqueErr], err)
+	}
+
+	// Updating a consumer with overlapping subjects should return an error.
+	_, err = mset.addConsumerWithAction(&ConsumerConfig{
+		Durable:        "C3",
+		FilterSubjects: []string{"one", "two", "three", "four"},
+		AckPolicy:      AckExplicit,
+	}, ActionUpdate)
+	require_Error(t, err)
+	if !IsNatsErr(err, JSConsumerWQConsumerNotUniqueErr) {
+		t.Errorf("want error %q, got %q", ApiErrors[JSConsumerWQConsumerNotUniqueErr], err)
+	}
+}
+
 func TestJetStreamConsumerActionsViaAPI(t *testing.T) {
 
 	s := RunBasicJetStreamServer(t)

server/stream.go

@@ -5266,9 +5266,13 @@ func (mset *stream) Store() StreamStore {
 
 // Determines if the new proposed partition is unique amongst all consumers.
 // Lock should be held.
-func (mset *stream) partitionUnique(partitions []string) bool {
+func (mset *stream) partitionUnique(name string, partitions []string) bool {
 	for _, partition := range partitions {
-		for _, o := range mset.consumers {
+		for n, o := range mset.consumers {
+			// Skip the consumer being checked.
+			if n == name {
+				continue
+			}
 			if o.subjf == nil {
 				return false
 			}