For a field of type google.protobuf.Empty, FieldMaskFromRequestBody does not generate any fieldmask about grpc-gateway HOT 3 CLOSED

Here are the diffs for a failing test:

diff --git a/runtime/fieldmask_test.go b/runtime/fieldmask_test.go
index 1af66ab4..3db815ef 100644
--- a/runtime/fieldmask_test.go
+++ b/runtime/fieldmask_test.go
@@ -28,6 +28,13 @@ func TestFieldMaskFromRequestBody(t *testing.T) {
                        name:     "empty",
                        expected: newFieldMask(),
                },
+               {
+                       name: "EmptyMessage",
+
+                       msg:      &examplepb.ABitOfEverything{},
+                       input:    `{"oneof_empty": {}}`,
+                       expected: newFieldMask("oneof_empty"),
+               },
                {
                        name: "simple",

from grpc-gateway.

Thanks for your issue! I'm a little confused - you have a field where the presence of an empty message is significant? Surely an empty value isn't set or unset, it's just empty? What is the semantic meaning of a "set" empty value?

That said, if you want to contribute a fix for this, I'm all for it. I just don't really get it.

from grpc-gateway.

Thanks for response. Empty messages are useful as default choice in oneof. Similar to how it is defined here: https://github.com/grpc-ecosystem/grpc-gateway/blob/main/examples/internal/proto/examplepb/a_bit_of_everything.proto#L295

Here is another example. Lets say, you want the user to select a site and also give the user an option to explicitly select "all_sites", you could define a oneof like this:

oneof site_option {
    google.protobuf.Empty all_sites = 1;
    string site = 2;
  }

Now, when someone sends all_sites, I was hoping that I will get all_sites set in fieldMask, but it is not set.

from grpc-gateway.