[ADDED] Lookup stream name by subject

jetstream/errors.go

@@ -109,6 +109,9 @@ var (
 	// ErrInvalidStreamName is returned when the provided stream name is invalid (contains '.').
 	ErrInvalidStreamName JetStreamError = &jsError{message: "invalid stream name"}
 
+	// ErrInvalidSubject is returned when the provided subject name is invalid.
+	ErrInvalidSubject JetStreamError = &jsError{message: "invalid subject name"}
+
 	// ErrInvalidConsumerName is returned when the provided consumer name is invalid (contains '.').
 	ErrInvalidConsumerName JetStreamError = &jsError{message: "invalid consumer name"}
 

jetstream/jetstream.go

@@ -18,6 +18,7 @@ import (
 	"encoding/json"
 	"errors"
 	"fmt"
+	"regexp"
 	"strings"
 
 	"github.com/nats-io/nats.go"
@@ -68,6 +69,8 @@ type (
 		UpdateStream(context.Context, StreamConfig) (Stream, error)
 		// Stream returns a [Stream] hook for a given stream name
 		Stream(context.Context, string) (Stream, error)
+		// StreamNameBySubject returns a stream name stream listening on given subject
+		StreamNameBySubject(context.Context, string) (string, error)
 		// DeleteStream removes a stream with given name
 		DeleteStream(context.Context, string) error
 		// ListStreams returns StreamInfoLister enabling iterating over a channel of stream infos
@@ -186,8 +189,14 @@ type (
 		apiPaged
 		Streams []string `json:"streams"`
 	}
+
+	streamsRequest struct {
+		Subject string `json:"subject,omitempty"`
+	}
 )
 
+var subjectRegexp = regexp.MustCompile(`^[^ >]*[>]?$`)
+
 // New returns a enw JetStream instance
 //
 // Available options:
@@ -494,6 +503,16 @@ func validateStreamName(stream string) error {
 	return nil
 }
 
+func validateSubject(subject string) error {
+	if subject == "" {
+		return fmt.Errorf("%w: %s", ErrInvalidSubject, "subject cannot be empty")
+	}
+	if !subjectRegexp.MatchString(subject) {
+		return fmt.Errorf("%w: %s", ErrInvalidSubject, subject)
+	}
+	return nil
+}
+
 func (js *jetStream) AccountInfo(ctx context.Context) (*AccountInfo, error) {
 	var resp accountInfoResponse
 
@@ -591,6 +610,32 @@ func (js *jetStream) StreamNames(ctx context.Context) StreamNameLister {
 	return l
 }
 
+func (js *jetStream) StreamNameBySubject(ctx context.Context, subject string) (string, error) {
+	if err := validateSubject(subject); err != nil {
+		return "", err
+	}
+	streamsSubject := apiSubj(js.apiPrefix, apiStreams)
+
+	r := &streamsRequest{Subject: subject}
+	req, err := json.Marshal(r)
+	if err != nil {
+		return "", err
+	}
+	var resp streamNamesResponse
+	_, err = js.apiRequestJSON(ctx, streamsSubject, &resp, req)
+	if err != nil {
+		return "", err
+	}
+	if resp.Error != nil {
+		return "", resp.Error
+	}
+	if len(resp.Streams) == 0 {
+		return "", ErrStreamNotFound
+	}
+
+	return resp.Streams[0], nil
+}
+
 // Name returns a channel allowing retrieval of stream names returned by [StreamNames]
 func (s *streamLister) Name() <-chan string {
 	return s.names

jetstream/message_test.go → jetstream/jetstream_test.go

@@ -15,6 +15,7 @@ package jetstream
 
 import (
 	"errors"
+	"fmt"
 	"testing"
 	"time"
 
@@ -80,3 +81,38 @@ func TestMessageMetadata(t *testing.T) {
 		})
 	}
 }
+
+func TestValidateSubject(t *testing.T) {
+	tests := []struct {
+		subject   string
+		withError bool
+	}{
+		{"test.A", false},
+		{"test.*", false},
+		{"*", false},
+		{"*.*", false},
+		{"test.*.A", false},
+		{"test.>", false},
+		{">", false},
+		{">.", true},
+		{"test.>.A", true},
+		{"", true},
+		{"test A", true},
+	}
+
+	for _, test := range tests {
+		tName := fmt.Sprintf("subj=%s,err=%t", test.subject, test.withError)
+		t.Run(tName, func(t *testing.T) {
+			err := validateSubject(test.subject)
+			if test.withError {
+				if err == nil {
+					t.Fatal("Expected error; got nil")
+				}
+				return
+			}
+			if err != nil {
+				t.Fatalf("Unexpected error: %v", err)
+			}
+		})
+	}
+}

jetstream/test/jetstream_test.go

@@ -928,3 +928,81 @@ func TestJetStream_DeleteConsumer(t *testing.T) {
 		})
 	}
 }
+
+func TestStreamNameBySubject(t *testing.T) {
+	tests := []struct {
+		name      string
+		subject   string
+		withError error
+		expected  string
+	}{
+		{
+			name:     "get stream name by subject explicit",
+			subject:  "FOO.123",
+			expected: "foo",
+		},
+		{
+			name:     "get stream name by subject with wildcard",
+			subject:  "BAR.*",
+			expected: "bar",
+		},
+		{
+			name:     "match more than one stream, return the first one",
+			subject:  ">",
+			expected: "",
+		},
+		{
+			name:      "stream not found",
+			subject:   "BAR.XYZ",
+			withError: jetstream.ErrStreamNotFound,
+		},
+		{
+			name:      "invalid subject",
+			subject:   "FOO.>.123",
+			withError: jetstream.ErrInvalidSubject,
+		},
+	}
+
+	srv := RunBasicJetStreamServer()
+	defer shutdownJSServerAndRemoveStorage(t, srv)
+	nc, err := nats.Connect(srv.ClientURL())
+	if err != nil {
+		t.Fatalf("Unexpected error: %v", err)
+	}
+
+	js, err := jetstream.New(nc)
+	if err != nil {
+		t.Fatalf("Unexpected error: %v", err)
+	}
+	defer nc.Close()
+
+	ctx, cancel := context.WithTimeout(context.Background(), 5*time.Second)
+	defer cancel()
+	_, err = js.CreateStream(ctx, jetstream.StreamConfig{Name: "foo", Subjects: []string{"FOO.*"}})
+	if err != nil {
+		t.Fatalf("Unexpected error: %v", err)
+	}
+	_, err = js.CreateStream(ctx, jetstream.StreamConfig{Name: "bar", Subjects: []string{"BAR.ABC"}})
+	if err != nil {
+		t.Fatalf("Unexpected error: %v", err)
+	}
+
+	for _, test := range tests {
+		t.Run(test.name, func(t *testing.T) {
+			name, err := js.StreamNameBySubject(ctx, test.subject)
+			if test.withError != nil {
+				if err == nil || !errors.Is(err, test.withError) {
+					t.Fatalf("Expected error: %v; got: %v", test.withError, err)
+				}
+				return
+			}
+			if err != nil {
+				t.Fatalf("Unexpected error: %v", err)
+			}
+			if test.expected != "" && name != test.expected {
+				t.Fatalf("Unexpected stream name; want: %s; got: %s", test.expected, name)
+			}
+
+		})
+	}
+}

micro/service.go

@@ -263,7 +263,7 @@ var (
 	// this regular expression is suggested regexp for semver validation: https://semver.org/
 	semVerRegexp  = regexp.MustCompile(`^(0|[1-9]\d*)\.(0|[1-9]\d*)\.(0|[1-9]\d*)(?:-((?:0|[1-9]\d*|\d*[a-zA-Z-][0-9a-zA-Z-]*)(?:\.(?:0|[1-9]\d*|\d*[a-zA-Z-][0-9a-zA-Z-]*))*))?(?:\+([0-9a-zA-Z-]+(?:\.[0-9a-zA-Z-]+)*))?$`)
 	nameRegexp    = regexp.MustCompile(`^[A-Za-z0-9\-_]+$`)
-	subjectRegexp = regexp.MustCompile(`^[^ >]+[>]?$`)
+	subjectRegexp = regexp.MustCompile(`^[^ >]*[>]?$`)
 )
 
 // Common errors returned by the Service framework.