Make lookupStreamBySubject public

js.go

@@ -1529,7 +1529,7 @@ func (js *js) subscribe(subj, queue string, cb MsgHandler, ch chan *Msg, isSync,
 
 	// Find the stream mapped to the subject if not bound to a stream already.
 	if o.stream == _EMPTY_ {
-		stream, err = js.lookupStreamBySubject(subj)
+		stream, err = js.StreamNameBySubject(subj)
 		if err != nil {
 			return nil, err
 		}
@@ -2144,7 +2144,8 @@ type streamNamesResponse struct {
 	Streams []string `json:"streams"`
 }
 
-func (js *js) lookupStreamBySubject(subj string) (string, error) {
+// StreamNameBySubject returns a stream name that matches the subject.
+func (js *js) StreamNameBySubject(subj string) (string, error) {
 	var slr streamNamesResponse
 	req := &streamRequest{subj}
 	j, err := json.Marshal(req)

js_test.go

@@ -1230,3 +1230,34 @@ func TestJetStreamStreamInfoWithSubjectDetails(t *testing.T) {
 		t.Fatalf("expected 0 subjects details from StreamInfo, but got %d instead", len(result.State.Subjects))
 	}
 }
+
+func StreamNameBySubject(t *testing.T) {
+
+	s := RunBasicJetStreamServer()
+	defer shutdownJSServerAndRemoveStorage(t, s)
+
+	nc, js := jsClient(t, s)
+	defer nc.Close()
+
+	var err error
+
+	_, err = js.AddStream(&StreamConfig{
+		Name:     "TEST",
+		Subjects: []string{"test.*"},
+	})
+	if err != nil {
+		t.Fatalf("Unexpected error: %v", err)
+	}
+
+	stream, err := js.StreamNameBySubject("test.*")
+	if err != nil {
+		t.Fatalf("lookup stream should succeed for %s", "test.*")
+	}
+	if stream != "TEST" {
+		t.Fatalf("returned stream should be 'TEST'")
+	}
+
+	if _, err := js.StreamNameBySubject("bad"); err == nil {
+		t.Fatalf("error should be nil, no stream with name 'bad'")
+	}
+}

jsm.go

@@ -93,6 +93,9 @@ type JetStreamManager interface {
 
 	// AccountInfo retrieves info about the JetStream usage from an account.
 	AccountInfo(opts ...JSOpt) (*AccountInfo, error)
+
+	// Returns a stream matching given subject.
+	StreamNameBySubject(string) (string, error)
 }
 
 // StreamConfig will determine the properties for a stream.