allow sending trailers from server handler

src/csharp/Grpc.Core/Internal/AsyncCallServer.cs

@@ -101,14 +101,17 @@ namespace Grpc.Core.Internal
         /// Only one pending send action is allowed at any given time.
         /// completionDelegate is called when the operation finishes.
         /// </summary>
-        public void StartSendStatusFromServer(Status status, AsyncCompletionDelegate<object> completionDelegate)
+        public void StartSendStatusFromServer(Status status, Metadata trailers, AsyncCompletionDelegate<object> completionDelegate)
         {
             lock (myLock)
             {
                 Preconditions.CheckNotNull(completionDelegate, "Completion delegate cannot be null");
                 CheckSendingAllowed();
 
-                call.StartSendStatusFromServer(status, HandleHalfclosed);
+                using (var metadataArray = MetadataArraySafeHandle.Create(trailers))
+                {
+                    call.StartSendStatusFromServer(status, HandleHalfclosed, metadataArray);
+                }
                 halfcloseRequested = true;
                 readingDone = true;
                 sendCompletionDelegate = completionDelegate;

src/csharp/Grpc.Core/Internal/CallSafeHandle.cs

@@ -81,7 +81,7 @@ namespace Grpc.Core.Internal
 
         [DllImport("grpc_csharp_ext.dll")]
         static extern GRPCCallError grpcsharp_call_send_status_from_server(CallSafeHandle call, 
-            BatchContextSafeHandle ctx, StatusCode statusCode, string statusMessage);
+            BatchContextSafeHandle ctx, StatusCode statusCode, string statusMessage, MetadataArraySafeHandle metadataArray);
 
         [DllImport("grpc_csharp_ext.dll")]
         static extern GRPCCallError grpcsharp_call_recv_message(CallSafeHandle call,
@@ -159,11 +159,11 @@ namespace Grpc.Core.Internal
             grpcsharp_call_send_close_from_client(this, ctx).CheckOk();
         }
 
-        public void StartSendStatusFromServer(Status status, BatchCompletionDelegate callback)
+        public void StartSendStatusFromServer(Status status, BatchCompletionDelegate callback, MetadataArraySafeHandle metadataArray)
         {
             var ctx = BatchContextSafeHandle.Create();
             completionRegistry.RegisterBatchCompletion(ctx, callback);
-            grpcsharp_call_send_status_from_server(this, ctx, status.StatusCode, status.Detail).CheckOk();
+            grpcsharp_call_send_status_from_server(this, ctx, status.StatusCode, status.Detail, metadataArray).CheckOk();
         }
 
         public void StartReceiveMessage(BatchCompletionDelegate callback)

src/csharp/Grpc.Core/Internal/ServerCallHandler.cs

@@ -72,13 +72,13 @@ namespace Grpc.Core.Internal
             var responseStream = new ServerResponseStream<TRequest, TResponse>(asyncCall);
 
             Status status;
+            var context = HandlerUtils.NewContext(newRpc);
             try
             {
                 Preconditions.CheckArgument(await requestStream.MoveNext());
                 var request = requestStream.Current;
                 // TODO(jtattermusch): we need to read the full stream so that native callhandle gets deallocated.
                 Preconditions.CheckArgument(!await requestStream.MoveNext());
-                var context = HandlerUtils.NewContext(newRpc);
                 var result = await handler(context, request);
                 status = context.Status;
                 await responseStream.WriteAsync(result);
@@ -90,7 +90,7 @@ namespace Grpc.Core.Internal
             }
             try
             {
-                await responseStream.WriteStatusAsync(status);
+                await responseStream.WriteStatusAsync(status, context.ResponseTrailers);
             }
             catch (OperationCanceledException)
             {
@@ -126,14 +126,13 @@ namespace Grpc.Core.Internal
             var responseStream = new ServerResponseStream<TRequest, TResponse>(asyncCall);
 
             Status status;
+            var context = HandlerUtils.NewContext(newRpc);
             try
             {
                 Preconditions.CheckArgument(await requestStream.MoveNext());
                 var request = requestStream.Current;
                 // TODO(jtattermusch): we need to read the full stream so that native callhandle gets deallocated.
                 Preconditions.CheckArgument(!await requestStream.MoveNext());
-
-                var context = HandlerUtils.NewContext(newRpc);
                 await handler(context, request, responseStream);
                 status = context.Status;
             }
@@ -145,7 +144,7 @@ namespace Grpc.Core.Internal
 
             try
             {
-                await responseStream.WriteStatusAsync(status);
+                await responseStream.WriteStatusAsync(status, context.ResponseTrailers);
             }
             catch (OperationCanceledException)
             {
@@ -179,9 +178,10 @@ namespace Grpc.Core.Internal
             var finishedTask = asyncCall.ServerSideCallAsync();
             var requestStream = new ServerRequestStream<TRequest, TResponse>(asyncCall);
             var responseStream = new ServerResponseStream<TRequest, TResponse>(asyncCall);
-            var context = HandlerUtils.NewContext(newRpc);
+
 
             Status status;
+            var context = HandlerUtils.NewContext(newRpc);
             try
             {
                 var result = await handler(context, requestStream);
@@ -203,7 +203,7 @@ namespace Grpc.Core.Internal
 
             try
             {
-                await responseStream.WriteStatusAsync(status);
+                await responseStream.WriteStatusAsync(status, context.ResponseTrailers);
             }
             catch (OperationCanceledException)
             {
@@ -237,9 +237,9 @@ namespace Grpc.Core.Internal
             var finishedTask = asyncCall.ServerSideCallAsync();
             var requestStream = new ServerRequestStream<TRequest, TResponse>(asyncCall);
             var responseStream = new ServerResponseStream<TRequest, TResponse>(asyncCall);
-            var context = HandlerUtils.NewContext(newRpc);
 
             Status status;
+            var context = HandlerUtils.NewContext(newRpc);
             try
             {
                 await handler(context, requestStream, responseStream);
@@ -252,7 +252,7 @@ namespace Grpc.Core.Internal
             }
             try
             {
-                await responseStream.WriteStatusAsync(status);
+                await responseStream.WriteStatusAsync(status, context.ResponseTrailers);
             }
             catch (OperationCanceledException)
             {
@@ -277,7 +277,7 @@ namespace Grpc.Core.Internal
             var requestStream = new ServerRequestStream<byte[], byte[]>(asyncCall);
             var responseStream = new ServerResponseStream<byte[], byte[]>(asyncCall);
 
-            await responseStream.WriteStatusAsync(new Status(StatusCode.Unimplemented, "No such method."));
+            await responseStream.WriteStatusAsync(new Status(StatusCode.Unimplemented, "No such method."), Metadata.Empty);
             await finishedTask;
         }
     }

src/csharp/Grpc.Core/Internal/ServerResponseStream.cs

@@ -56,10 +56,10 @@ namespace Grpc.Core.Internal
             return taskSource.Task;
         }
 
-        public Task WriteStatusAsync(Status status)
+        public Task WriteStatusAsync(Status status, Metadata trailers)
         {
             var taskSource = new AsyncCompletionTaskSource<object>();
-            call.StartSendStatusFromServer(status, taskSource.CompletionDelegate);
+            call.StartSendStatusFromServer(status, trailers, taskSource.CompletionDelegate);
             return taskSource.Task;
         }
     }

src/csharp/ext/grpc_csharp_ext.c

@@ -630,15 +630,20 @@ GPR_EXPORT grpc_call_error GPR_CALLTYPE
 grpcsharp_call_send_status_from_server(grpc_call *call,
                                        grpcsharp_batch_context *ctx,
                                        grpc_status_code status_code,
-                                       const char *status_details) {
+                                       const char *status_details,
+                                       grpc_metadata_array *trailing_metadata) {
   /* TODO: don't use magic number */
   grpc_op ops[1];
   ops[0].op = GRPC_OP_SEND_STATUS_FROM_SERVER;
   ops[0].data.send_status_from_server.status = status_code;
   ops[0].data.send_status_from_server.status_details =
       gpr_strdup(status_details);
-  ops[0].data.send_status_from_server.trailing_metadata = NULL;
-  ops[0].data.send_status_from_server.trailing_metadata_count = 0;
+  grpcsharp_metadata_array_move(&(ctx->send_status_from_server.trailing_metadata),
+                                  trailing_metadata);
+  ops[0].data.send_status_from_server.trailing_metadata_count =
+      ctx->send_status_from_server.trailing_metadata.count;
+  ops[0].data.send_status_from_server.trailing_metadata =
+      ctx->send_status_from_server.trailing_metadata.metadata;
   ops[0].flags = 0;
 
   return grpc_call_start_batch(call, ops, sizeof(ops) / sizeof(ops[0]), ctx);