handling send-only configurations

Author: timbussmann

src/NServiceBus.AzureFunctions.InProcess.ServiceBus/Serverless/TransportWrapper/ServerlessTransport.cs

@@ -31,7 +31,11 @@ public override async Task<TransportInfrastructure> Initialize(HostSettings host
                 .ConfigureAwait(false);
 
             var serverlessTransportInfrastructure = new ServerlessTransportInfrastructure(baseTransportInfrastructure);
-            PipelineInvoker = (PipelineInvoker)serverlessTransportInfrastructure.Receivers[MainReceiverId];
+
+            PipelineInvoker = receivers.Length > 0
+                ? (PipelineInvoker)serverlessTransportInfrastructure.Receivers[MainReceiverId]
+                : new PipelineInvoker(new NullReceiver()); // send-only endpoint
+
             return serverlessTransportInfrastructure;
         }
 
@@ -53,4 +57,21 @@ public override IReadOnlyCollection<TransportTransactionMode> GetSupportedTransa
             TransportTransactionMode.SendsAtomicWithReceive
         };
     }
+
+    class NullReceiver : IMessageReceiver
+    {
+        public Task Initialize(PushRuntimeSettings limitations, OnMessage onMessage, OnError onError,
+            CancellationToken cancellationToken = new CancellationToken()) =>
+            throw new System.NotImplementedException();
+
+        public Task StartReceive(CancellationToken cancellationToken = new CancellationToken()) => throw new System.NotImplementedException();
+
+        public Task ChangeConcurrency(PushRuntimeSettings limitations, CancellationToken cancellationToken = new CancellationToken()) => throw new System.NotImplementedException();
+
+        public Task StopReceive(CancellationToken cancellationToken = new CancellationToken()) => throw new System.NotImplementedException();
+
+        public ISubscriptionManager Subscriptions { get; }
+        public string Id { get; }
+        public string ReceiveAddress { get; }
+    }
 }