Fix GrpcWebHandler not always resetting HTTP version back to 2.0 (#810)

Author: JamesNK

examples/Blazor/Server/Program.cs

@@ -16,25 +16,23 @@
 
 #endregion
 
-using Microsoft.AspNetCore;
 using Microsoft.AspNetCore.Hosting;
-using Microsoft.Extensions.Configuration;
+using Microsoft.Extensions.Hosting;
 
 namespace Server
 {
     public class Program
     {
         public static void Main(string[] args)
         {
-            BuildWebHost(args).Run();
+            CreateHostBuilder(args).Build().Run();
         }
 
-        public static IWebHost BuildWebHost(string[] args) =>
-            WebHost.CreateDefaultBuilder(args)
-                .UseConfiguration(new ConfigurationBuilder()
-                    .AddCommandLine(args)
-                    .Build())
-                .UseStartup<Startup>()
-                .Build();
+        public static IHostBuilder CreateHostBuilder(string[] args) =>
+            Host.CreateDefaultBuilder(args)
+                .ConfigureWebHostDefaults(webBuilder =>
+                {
+                    webBuilder.UseStartup<Startup>();
+                });
     }
 }

examples/Blazor/Server/appsettings.Development.json

@@ -0,0 +1,10 @@
+{
+  "Logging": {
+    "LogLevel": {
+      "Default": "Debug",
+      "System": "Information",
+      "Grpc": "Information",
+      "Microsoft": "Information"
+    }
+  }
+}

examples/Blazor/Server/appsettings.json

@@ -0,0 +1,8 @@
+{
+  "Logging": {
+    "LogLevel": {
+      "Default": "Information"
+    }
+  },
+  "AllowedHosts": "*"
+}

src/Grpc.Net.Client.Web/GrpcWebHandler.cs

@@ -113,23 +113,27 @@ private async Task<HttpResponseMessage> SendAsyncCore(HttpRequestMessage request
             request.Content = new GrpcWebRequestContent(request.Content, _mode);
             if (_httpVersion != null)
             {
+                // This doesn't guarantee that the specified version is used. Some handlers will ignore it.
+                // For example, version in the browser always negotiated by the browser and HttpClient
+                // uses what the browser has negotiated.
                 request.Version = _httpVersion;
             }
 
             var response = await base.SendAsync(request, cancellationToken).ConfigureAwait(false);
 
-            if (_httpVersion != null)
-            {
-                // If a HTTP version has been specified then we need to reset it back to 2.0.
-                // The gRPC client validates HTTP version 2.0.
-                response.Version = HttpVersion.Version20;
-            }
-
             if (IsMatchingResponseContentType(_mode, response.Content.Headers.ContentType?.MediaType))
             {
                 response.Content = new GrpcWebResponseContent(response.Content, _mode, response.TrailingHeaders);
             }
 
+            // The gRPC client validates HTTP version 2.0 and will error if it isn't. Always set
+            // the version to 2.0, even for non-gRPC content type. The client maps HTTP status codes
+            // to gRPC statuses, e.g. HTTP 404 -> gRPC unimplemented.
+            //
+            // Note: Some handlers don't correctly set HttpResponseMessage.Version.
+            // We can't rely on it being set correctly. It is safest to always set it to 2.0.
+            response.Version = HttpVersion.Version20;
+
             return response;
         }