Fix client results with Hub<T> IHubContext (#41763)

Author: BrennanConroy

src/SignalR/server/Core/src/Internal/HubClients`T.cs

@@ -15,6 +15,11 @@ public HubClients(HubLifetimeManager<THub> lifetimeManager)
 
     public T All { get; }
 
+    public T Single(string connectionId)
+    {
+        return TypedClientBuilder<T>.Build(new SingleClientProxyWithInvoke<THub>(_lifetimeManager, connectionId));
+    }
+
     public T AllExcept(IReadOnlyList<string> excludedConnectionIds)
     {
         return TypedClientBuilder<T>.Build(new AllClientsExceptProxy<THub>(_lifetimeManager, excludedConnectionIds));

src/SignalR/server/SignalR/test/HubConnectionHandlerTestUtils/Hubs.cs

@@ -530,6 +530,8 @@ public interface Test
 {
     Task Send(string message);
     Task Broadcast(string message);
+
+    Task<int> GetClientResult(int value);
 }
 
 public class OnConnectedThrowsHub : Hub

src/SignalR/server/SignalR/test/HubConnectionHandlerTests.ClientResult.cs

@@ -103,4 +103,68 @@ public async Task ThrowsWhenParallelHubInvokesNotEnabled()
             }
         }
     }
+
+    [Fact]
+    public async Task CanUseClientResultsWithIHubContext()
+    {
+        using (StartVerifiableLog())
+        {
+            var serviceProvider = HubConnectionHandlerTestUtils.CreateServiceProvider(null, LoggerFactory);
+            var connectionHandler = serviceProvider.GetService<HubConnectionHandler<MethodHub>>();
+
+            using var client = new TestClient();
+
+            var connectionHandlerTask = await client.ConnectAsync(connectionHandler);
+
+            // Wait for a connection, or for the endpoint to fail.
+            await client.Connected.OrThrowIfOtherFails(connectionHandlerTask).DefaultTimeout();
+
+            var context = serviceProvider.GetRequiredService<IHubContext<MethodHub>>();
+            var resultTask = context.Clients.Single(client.Connection.ConnectionId).InvokeAsync<int>("GetClientResult", 1);
+
+            var message = await client.ReadAsync().DefaultTimeout();
+            var invocation = Assert.IsType<InvocationMessage>(message);
+
+            Assert.Single(invocation.Arguments);
+            Assert.Equal(1L, invocation.Arguments[0]);
+            Assert.Equal("GetClientResult", invocation.Target);
+
+            await client.SendHubMessageAsync(CompletionMessage.WithResult(invocation.InvocationId, 2)).DefaultTimeout();
+
+            var result = await resultTask.DefaultTimeout();
+            Assert.Equal(2, result);
+        }
+    }
+
+    [Fact]
+    public async Task CanUseClientResultsWithIHubContextT()
+    {
+        using (StartVerifiableLog())
+        {
+            var serviceProvider = HubConnectionHandlerTestUtils.CreateServiceProvider(null, LoggerFactory);
+            var connectionHandler = serviceProvider.GetService<HubConnectionHandler<HubT>>();
+
+            using var client = new TestClient();
+
+            var connectionHandlerTask = await client.ConnectAsync(connectionHandler);
+
+            // Wait for a connection, or for the endpoint to fail.
+            await client.Connected.OrThrowIfOtherFails(connectionHandlerTask).DefaultTimeout();
+
+            var context = serviceProvider.GetRequiredService<IHubContext<HubT, Test>>();
+            var resultTask = context.Clients.Single(client.Connection.ConnectionId).GetClientResult(1);
+
+            var message = await client.ReadAsync().DefaultTimeout();
+            var invocation = Assert.IsType<InvocationMessage>(message);
+
+            Assert.Single(invocation.Arguments);
+            Assert.Equal(1L, invocation.Arguments[0]);
+            Assert.Equal("GetClientResult", invocation.Target);
+
+            await client.SendHubMessageAsync(CompletionMessage.WithResult(invocation.InvocationId, 2)).DefaultTimeout();
+
+            var result = await resultTask.DefaultTimeout();
+            Assert.Equal(2, result);
+        }
+    }
 }