Bypasses deserialization of return value when 'InvokeVoidAsync' is used.

src/Components/Shared/src/WebAssemblyJSInteropInternalCalls.cs

@@ -19,7 +19,7 @@ internal static class InternalCalls
         // We're passing asyncHandle by ref not because we want it to be writable, but so it gets
         // passed as a pointer (4 bytes). We can pass 4-byte values, but not 8-byte ones.
         [MethodImpl(MethodImplOptions.InternalCall)]
-        public static extern string InvokeJSMarshalled(out string exception, ref long asyncHandle, string functionIdentifier, string argsJson);
+        public static extern string InvokeJSMarshalled(out string exception, ref long asyncHandle, string functionIdentifier, string argsJson, bool treatReturnAsVoid);
 
         [MethodImpl(MethodImplOptions.InternalCall)]
         public static extern TRes InvokeJSUnmarshalled<T0, T1, T2, TRes>(out string exception, string functionIdentifier, [AllowNull] T0 arg0, [AllowNull] T1 arg1, [AllowNull] T2 arg2);

src/Components/WebAssembly/JSInterop/src/WebAssemblyJSRuntime.cs

@@ -14,19 +14,19 @@ namespace Microsoft.JSInterop.WebAssembly
     public abstract class WebAssemblyJSRuntime : JSInProcessRuntime
     {
         /// <inheritdoc />
-        protected override string InvokeJS(string identifier, string argsJson)
+        protected override string InvokeJS(string identifier, string argsJson, bool treatReturnAsVoid)
         {
             var noAsyncHandle = default(long);
-            var result = InternalCalls.InvokeJSMarshalled(out var exception, ref noAsyncHandle, identifier, argsJson);
+            var result = InternalCalls.InvokeJSMarshalled(out var exception, ref noAsyncHandle, identifier, argsJson, treatReturnAsVoid);
             return exception != null
                 ? throw new JSException(exception)
                 : result;
         }
 
         /// <inheritdoc />
-        protected override void BeginInvokeJS(long asyncHandle, string identifier, string argsJson)
+        protected override void BeginInvokeJS(long asyncHandle, string identifier, string argsJson, bool treatReturnAsVoid)
         {
-            InternalCalls.InvokeJSMarshalled(out _, ref asyncHandle, identifier, argsJson);
+            InternalCalls.InvokeJSMarshalled(out _, ref asyncHandle, identifier, argsJson, treatReturnAsVoid);
         }
 
         protected override void EndInvokeDotNet(DotNetInvocationInfo callInfo, in DotNetInvocationResult dispatchResult)
@@ -39,7 +39,7 @@ protected override void EndInvokeDotNet(DotNetInvocationInfo callInfo, in DotNet
             // We pass 0 as the async handle because we don't want the JS-side code to
             // send back any notification (we're just providing a result for an existing async call)
             var args = JsonSerializer.Serialize(new[] { callInfo.CallId, dispatchResult.Success, resultOrError }, JsonSerializerOptions);
-            BeginInvokeJS(0, "DotNet.jsCallDispatcher.endInvokeDotNetFromJS", args);
+            BeginInvokeJS(0, "DotNet.jsCallDispatcher.endInvokeDotNetFromJS", args, false);
         }
 
         /// <summary>

src/JSInterop/Microsoft.JSInterop.JS/src/src/Microsoft.JSInterop.ts

@@ -167,11 +167,12 @@ export module DotNet {
      *
      * @param identifier Identifies the globally-reachable function to invoke.
      * @param argsJson JSON representation of arguments to be passed to the function.
+     * @param treatReturnAsVoid Ignore any result that is returned and treat as Void.
      * @returns JSON representation of the invocation result.
      */
-    invokeJSFromDotNet: (identifier: string, argsJson: string) => {
+    invokeJSFromDotNet: (identifier: string, argsJson: string, treatReturnAsVoid: boolean) => {
       const result = findJSFunction(identifier).apply(null, parseJsonWithRevivers(argsJson));
-      return result === null || result === undefined
+      return result === null || result === undefined || treatReturnAsVoid === true
         ? null
         : JSON.stringify(result, argReplacer);
     },

src/JSInterop/Microsoft.JSInterop/src/JSInProcessRuntime.cs

@@ -21,7 +21,7 @@ public abstract class JSInProcessRuntime : JSRuntime, IJSInProcessRuntime
         [return: MaybeNull]
         public TValue Invoke<TValue>(string identifier, params object[] args)
         {
-            var resultJson = InvokeJS(identifier, JsonSerializer.Serialize(args, JsonSerializerOptions));
+            var resultJson = InvokeJS(identifier, JsonSerializer.Serialize(args, JsonSerializerOptions), typeof(TValue) == typeof(VoidReturn));
             if (resultJson is null)
             {
                 return default;
@@ -35,7 +35,8 @@ public TValue Invoke<TValue>(string identifier, params object[] args)
         /// </summary>
         /// <param name="identifier">The identifier for the function to invoke.</param>
         /// <param name="argsJson">A JSON representation of the arguments.</param>
+        /// <param name="treatReturnAsVoid">Ignore any result that is returned and treat as Void.</param>
         /// <returns>A JSON representation of the result.</returns>
-        protected abstract string? InvokeJS(string identifier, string? argsJson);
+        protected abstract string? InvokeJS(string identifier, string? argsJson, bool treatReturnAsVoid);
     }
 }

src/JSInterop/Microsoft.JSInterop/src/JSInProcessRuntimeExtensions.cs

@@ -23,7 +23,7 @@ public static void InvokeVoid(this IJSInProcessRuntime jsRuntime, string identif
                 throw new ArgumentNullException(nameof(jsRuntime));
             }
 
-            jsRuntime.Invoke<object>(identifier, args);
+            jsRuntime.Invoke<VoidReturn>(identifier, args);
         }
     }
 }

src/JSInterop/Microsoft.JSInterop/src/JSRuntime.cs

@@ -112,7 +112,7 @@ public ValueTask<TValue> InvokeAsync<TValue>(string identifier, CancellationToke
                 var argsJson = args?.Any() == true ?
                     JsonSerializer.Serialize(args, JsonSerializerOptions) :
                     null;
-                BeginInvokeJS(taskId, identifier, argsJson);
+                BeginInvokeJS(taskId, identifier, argsJson, typeof(TValue) == typeof(VoidReturn));
 
                 return new ValueTask<TValue>(tcs.Task);
             }
@@ -138,7 +138,8 @@ private void CleanupTasksAndRegistrations(long taskId)
         /// <param name="taskId">The identifier for the function invocation, or zero if no async callback is required.</param>
         /// <param name="identifier">The identifier for the function to invoke.</param>
         /// <param name="argsJson">A JSON representation of the arguments.</param>
-        protected abstract void BeginInvokeJS(long taskId, string identifier, string? argsJson);
+        /// <param name="treatReturnAsVoid">Ignore any result that is returned and treat as Void.</param>
+        protected abstract void BeginInvokeJS(long taskId, string identifier, string? argsJson, bool treatReturnAsVoid);
 
         /// <summary>
         /// Completes an async JS interop call from JavaScript to .NET
@@ -165,8 +166,7 @@ internal void EndInvokeJS(long taskId, bool succeeded, ref Utf8JsonReader jsonRe
                 if (succeeded)
                 {
                     var resultType = TaskGenericsUtil.GetTaskCompletionSourceResultType(tcs);
-
-                    var result = JsonSerializer.Deserialize(ref jsonReader, resultType, JsonSerializerOptions);
+                    var result = resultType != typeof(VoidReturn) ? JsonSerializer.Deserialize(ref jsonReader, resultType, JsonSerializerOptions) : null;
                     TaskGenericsUtil.SetTaskCompletionSourceResult(tcs, result);
                 }
                 else

src/JSInterop/Microsoft.JSInterop/src/JSRuntimeExtensions.cs

@@ -26,7 +26,7 @@ public static async ValueTask InvokeVoidAsync(this IJSRuntime jsRuntime, string
                 throw new ArgumentNullException(nameof(jsRuntime));
             }
 
-            await jsRuntime.InvokeAsync<object>(identifier, args);
+            await jsRuntime.InvokeAsync<VoidReturn>(identifier, args);
         }
 
         /// <summary>
@@ -91,7 +91,7 @@ public static async ValueTask InvokeVoidAsync(this IJSRuntime jsRuntime, string
                 throw new ArgumentNullException(nameof(jsRuntime));
             }
 
-            await jsRuntime.InvokeAsync<object>(identifier, cancellationToken, args);
+            await jsRuntime.InvokeAsync<VoidReturn>(identifier, cancellationToken, args);
         }
 
         /// <summary>
@@ -134,7 +134,7 @@ public static async ValueTask InvokeVoidAsync(this IJSRuntime jsRuntime, string
             using var cancellationTokenSource = timeout == Timeout.InfiniteTimeSpan ? null : new CancellationTokenSource(timeout);
             var cancellationToken = cancellationTokenSource?.Token ?? CancellationToken.None;
 
-            await jsRuntime.InvokeAsync<object>(identifier, cancellationToken, args);
+            await jsRuntime.InvokeAsync<VoidReturn>(identifier, cancellationToken, args);
         }
     }
 }

src/JSInterop/Microsoft.JSInterop/src/VoidReturn.cs

@@ -0,0 +1,11 @@
+using System.Threading.Tasks;
+
+namespace Microsoft.JSInterop
+{
+    /// <summary>
+    /// Used as a type for the <see cref="TaskCompletionSource{TResult}"/> that represents nothing should be returned.
+    /// </summary>
+    internal sealed class VoidReturn
+    {
+    }
+}