feat: Use noopTransport when no DSN provided

client.go

@@ -120,14 +120,13 @@ func NewClient(options ClientOptions) (*Client, error) {
 		options.Environment = os.Getenv("SENTRY_ENVIRONMENT")
 	}
 
-	dsn, err := NewDsn(options.Dsn)
-
-	if err != nil {
-		return nil, err
-	}
-
-	if dsn == nil {
-		Logger.Println("Sentry client initialized with an empty DSN")
+	var dsn *Dsn
+	if options.Dsn != "" {
+		var err error
+		dsn, err = NewDsn(options.Dsn)
+		if err != nil {
+			return nil, err
+		}
 	}
 
 	client := Client{
@@ -145,7 +144,11 @@ func (client *Client) setupTransport() {
 	transport := client.options.Transport
 
 	if transport == nil {
-		transport = NewHTTPTransport()
+		if client.options.Dsn == "" {
+			transport = new(noopTransport)
+		} else {
+			transport = NewHTTPTransport()
+		}
 	}
 
 	transport.Configure(client.options)
@@ -314,7 +317,7 @@ func (client *Client) processEvent(event *Event, hint *EventHint, scope EventMod
 	if options.SampleRate != 0.0 {
 		randomFloat := rand.New(rand.NewSource(time.Now().UnixNano())).Float32()
 		if randomFloat > options.SampleRate {
-			Logger.Println("Event dropped due to SampleRate hit")
+			Logger.Println("Event dropped due to SampleRate hit.")
 			return nil
 		}
 	}
@@ -329,7 +332,7 @@ func (client *Client) processEvent(event *Event, hint *EventHint, scope EventMod
 			h = hint
 		}
 		if event = options.BeforeSend(event, h); event == nil {
-			Logger.Println("Event dropped due to BeforeSend callback")
+			Logger.Println("Event dropped due to BeforeSend callback.")
 			return nil
 		}
 	}

client_test.go

@@ -5,6 +5,19 @@ import (
 	"testing"
 )
 
+func TestNewClientAllowsEmptyDSN(t *testing.T) {
+	transport := &TransportMock{}
+	client, err := NewClient(ClientOptions{
+		Transport: transport,
+	})
+	if err != nil {
+		t.Fatalf("expected no error when creating client without a DNS but got %v", err)
+	}
+
+	client.CaptureException(errors.New("custom error"), nil, &ScopeMock{})
+	assertEqual(t, transport.lastEvent.Exception[0].Value, "custom error")
+}
+
 type customComplexError struct {
 	Message string
 }

hub.go

@@ -206,7 +206,7 @@ func (hub *Hub) AddBreadcrumb(breadcrumb *Breadcrumb, hint *BreadcrumbHint) {
 			h = hint
 		}
 		if breadcrumb = options.BeforeBreadcrumb(breadcrumb, h); breadcrumb == nil {
-			Logger.Println("breadcrumb dropped due to BeforeBreadcrumb callback")
+			Logger.Println("breadcrumb dropped due to BeforeBreadcrumb callback.")
 			return
 		}
 	}

transport.go

@@ -156,7 +156,7 @@ func (t *HTTPTransport) SendEvent(event *Event) {
 		)
 	default:
 		t.wg.Done()
-		Logger.Println("Event dropped due to transport buffer being full")
+		Logger.Println("Event dropped due to transport buffer being full.")
 		// worker would block, drop the packet
 	}
 }
@@ -173,10 +173,10 @@ func (t *HTTPTransport) Flush(timeout time.Duration) bool {
 
 	select {
 	case <-c:
-		Logger.Println("Buffer flushed successfully")
+		Logger.Println("Buffer flushed successfully.")
 		return true
 	case <-time.After(timeout):
-		Logger.Println("Buffer flushing reached the timeout")
+		Logger.Println("Buffer flushing reached the timeout.")
 		return false
 	}
 }
@@ -294,3 +294,23 @@ func (t *HTTPSyncTransport) SendEvent(event *Event) {
 func (t *HTTPSyncTransport) Flush(_ time.Duration) bool {
 	return true
 }
+
+// ================================
+// noopTransport
+// ================================
+
+// noopTransport is an implementation of `Transport` interface which drops all the events.
+// Only used internally when an empty DSN is provided, which effectively disables the SDK.
+type noopTransport struct{}
+
+func (t *noopTransport) Configure(options ClientOptions) {
+	Logger.Println("Sentry client initialized with an empty DSN. Using noopTransport. No events will be delivered.")
+}
+
+func (t *noopTransport) SendEvent(event *Event) {
+	Logger.Println("Event dropped due to noopTransport usage.")
+}
+
+func (t *noopTransport) Flush(_ time.Duration) bool {
+	return true
+}