Fix Dependency Injection Conflict with Null Parameter in SignalR Hub Methods

src/SignalR/server/Core/src/Internal/DefaultHubDispatcher.cs

@@ -726,7 +726,26 @@ private void ReplaceArguments(HubMethodDescriptor descriptor, HubMethodInvocatio
         var hubInvocationArgumentPointer = 0;
         for (var parameterPointer = 0; parameterPointer < arguments.Length; parameterPointer++)
         {
-            if (hubMethodInvocationMessage.Arguments?.Length > hubInvocationArgumentPointer &&
+            // populate the synthetic arguments first
+            if (descriptor.IsServiceArgument(parameterPointer))
+            {
+                arguments[parameterPointer] = descriptor.GetService(scope.ServiceProvider, parameterPointer, descriptor.OriginalParameterTypes[parameterPointer]);
+            }
+            else if (descriptor.OriginalParameterTypes[parameterPointer] == typeof(CancellationToken))
+            {
+                cts = CancellationTokenSource.CreateLinkedTokenSource(connection.ConnectionAborted);
+                arguments[parameterPointer] = cts.Token;
+            }
+            else if (isStreamCall && ReflectionHelper.IsStreamingType(descriptor.OriginalParameterTypes[parameterPointer], mustBeDirectType: true))
+            {
+                Log.StartingParameterStream(_logger, hubMethodInvocationMessage.StreamIds![streamPointer]);
+                var itemType = descriptor.StreamingParameters![streamPointer];
+                arguments[parameterPointer] = connection.StreamTracker.AddStream(hubMethodInvocationMessage.StreamIds[streamPointer],
+                    itemType, descriptor.OriginalParameterTypes[parameterPointer]);
+
+                streamPointer++;
+            }
+           else if (hubMethodInvocationMessage.Arguments?.Length > hubInvocationArgumentPointer &&
                 (hubMethodInvocationMessage.Arguments[hubInvocationArgumentPointer] == null ||
                 descriptor.OriginalParameterTypes[parameterPointer].IsAssignableFrom(hubMethodInvocationMessage.Arguments[hubInvocationArgumentPointer]?.GetType())))
             {
@@ -736,29 +755,8 @@ private void ReplaceArguments(HubMethodDescriptor descriptor, HubMethodInvocatio
             }
             else
             {
-                if (descriptor.OriginalParameterTypes[parameterPointer] == typeof(CancellationToken))
-                {
-                    cts = CancellationTokenSource.CreateLinkedTokenSource(connection.ConnectionAborted);
-                    arguments[parameterPointer] = cts.Token;
-                }
-                else if (descriptor.IsServiceArgument(parameterPointer))
-                {
-                    arguments[parameterPointer] = descriptor.GetService(scope.ServiceProvider, parameterPointer, descriptor.OriginalParameterTypes[parameterPointer]);
-                }
-                else if (isStreamCall && ReflectionHelper.IsStreamingType(descriptor.OriginalParameterTypes[parameterPointer], mustBeDirectType: true))
-                {
-                    Log.StartingParameterStream(_logger, hubMethodInvocationMessage.StreamIds![streamPointer]);
-                    var itemType = descriptor.StreamingParameters![streamPointer];
-                    arguments[parameterPointer] = connection.StreamTracker.AddStream(hubMethodInvocationMessage.StreamIds[streamPointer],
-                        itemType, descriptor.OriginalParameterTypes[parameterPointer]);
-
-                    streamPointer++;
-                }
-                else
-                {
-                    // This should never happen
-                    Debug.Assert(false, $"Failed to bind argument of type '{descriptor.OriginalParameterTypes[parameterPointer].Name}' for hub method '{descriptor.MethodExecutor.MethodInfo.Name}'.");
-                }
+                // This should never happen
+                Debug.Assert(false, $"Failed to bind argument of type '{descriptor.OriginalParameterTypes[parameterPointer].Name}' for hub method '{descriptor.MethodExecutor.MethodInfo.Name}'.");
             }
         }
     }
@@ -896,4 +894,4 @@ private static void SetActivityError(Activity? activity, Exception ex)
         activity?.SetTag("error.type", ex.GetType().FullName);
         activity?.SetStatus(ActivityStatusCode.Error);
     }
-}
+}

src/SignalR/server/SignalR/test/Microsoft.AspNetCore.SignalR.Tests/HubConnectionHandlerTestUtils/Hubs.cs

@@ -1381,6 +1381,11 @@ public async Task<int> ServicesAndParams(int value, [FromService] Service1 servi
         }
         return total + value;
     }
+
+    public int ServiceWithStringAttribute([FromService] Service1 service, string value)
+    {
+        return 115;
+    }
 
     public int ServiceWithoutAttribute(Service1 service)
     {
@@ -1464,4 +1469,4 @@ public override async Task OnConnectedAsync()
             await Clients.Client(id).SendAsync("Test", 1);
         }
     }
-}
+}

src/SignalR/server/SignalR/test/Microsoft.AspNetCore.SignalR.Tests/HubConnectionHandlerTests.cs

@@ -4679,6 +4679,24 @@ public async Task HubMethodCanInjectService()
             Assert.True(Assert.IsType<bool>(res.Result));
         }
     }
+
+    // Regression test for https://github.com/dotnet/aspnetcore/issues/61491
+    [Fact]
+    public async Task HubMethodCanInjectServiceWithNullParameter()
+    {
+        var serviceProvider = HubConnectionHandlerTestUtils.CreateServiceProvider(provider =>
+        {
+            provider.AddSingleton<Service1>();
+        });
+        var connectionHandler = serviceProvider.GetService<HubConnectionHandler<ServicesHub>>();
+
+        using (var client = new TestClient())
+        {
+            var connectionHandlerTask = await client.ConnectAsync(connectionHandler).DefaultTimeout();
+            var res = await client.InvokeAsync(nameof(ServicesHub.ServiceWithStringAttribute),(string)null ).DefaultTimeout();
+            Assert.Equal(115L, res.Result);
+        }
+    }
 
     [Fact]
     public async Task HubMethodCanInjectMultipleServices()
@@ -5459,4 +5477,4 @@ public static async Task<IEnumerable<T>> ReadAllAsync<T>(this IAsyncEnumerable<T
 
         return result;
     }
-}
+}