Handle not exception errors from the server

lib/grpc/server/adapters/cowboy/handler.ex

@@ -376,6 +376,12 @@ defmodule GRPC.Server.Adapters.Cowboy.Handler do
     result = server.__call_rpc__(path, stream)
 
     case result do
+      {:ok, _stream, error = %GRPC.RPCError{message: nil, status: status}} ->
+        {:error, %{error | message: GRPC.Status.status_message(status)}}
+
+      {:ok, _stream, error = %GRPC.RPCError{}} ->
+        {:error, error}
+
       {:ok, stream, response} ->
         stream
         |> GRPC.Server.send_reply(response)

test/grpc/integration/server_test.exs

@@ -60,6 +60,19 @@ defmodule GRPC.Integration.ServerTest do
       raise "unknown error(This is a test, please ignore it)"
     end
 
+    def say_hello(%{name: "handled error"}, _stream) do
+      %GRPC.RPCError{
+        status: GRPC.Status.unauthenticated(),
+        message: "Please authenticate"
+      }
+    end
+
+    def say_hello(%{name: "handled error without message"}, _stream) do
+      %GRPC.RPCError{
+        status: GRPC.Status.unauthenticated()
+      }
+    end
+
     def say_hello(_req, _stream) do
       raise GRPC.RPCError, status: GRPC.Status.unauthenticated(), message: "Please authenticate"
     end
@@ -172,6 +185,33 @@ defmodule GRPC.Integration.ServerTest do
     end)
   end
 
+  test "return errors for handled errors" do
+    run_server([HelloErrorServer], fn port ->
+      {:ok, channel} = GRPC.Stub.connect("localhost:#{port}")
+      req = Helloworld.HelloRequest.new(name: "handled error")
+      {:error, reply} = channel |> Helloworld.Greeter.Stub.say_hello(req)
+
+      assert %GRPC.RPCError{
+               status: GRPC.Status.unauthenticated(),
+               message: "Please authenticate"
+             } == reply
+    end)
+  end
+
+  test "return errors for handled errors with the default message of the status" do
+    run_server([HelloErrorServer], fn port ->
+      {:ok, channel} = GRPC.Stub.connect("localhost:#{port}")
+      req = Helloworld.HelloRequest.new(name: "handled error without message")
+      {:error, reply} = channel |> Helloworld.Greeter.Stub.say_hello(req)
+
+      assert %GRPC.RPCError{
+               status: GRPC.Status.unauthenticated(),
+               message:
+                 "The request does not have valid authentication credentials for the operation"
+             } == reply
+    end)
+  end
+
   test "returns appropriate error for stream requests" do
     run_server([FeatureErrorServer], fn port ->
       {:ok, channel} = GRPC.Stub.connect("localhost:#{port}")