[Question] The `update_mask` field in PATCH method request does not work

[RyoJerryYu]

In gRPC-Gateway , there is a patch feature, aimed to allow a resource to be partially updated.

Patch feature | gRPC-Gateway

If a binding is mapped to patch and the request message has exactly one FieldMask message in it, additional code is rendered for the gateway handler that will populate the FieldMask based on the request body.

It means if I have a method like this:

service AppSvc {
  rpc UpdateApp(UpdateAppReq) returns (UpdateAppResp) {
    option (google.api.http) = {
      patch: "/api/v1/apps/{app.id}"
      body: "app"
    };
    option (google.api.method_signature) = "app,update_mask";
  }
}

message UpdateAppReq {
  App app = 1;
  google.protobuf.FieldMask update_mask = 2; // 由 gRPC-Gateway 框架填入
}
message UpdateAppResp {
  App app = 1;
}

And do a PATCH request:

curl -X 'PATCH' \
  'http://localhost:8000/api/v1/apps/8' \
  -H 'accept: application/json' \
  -H 'Content-Type: application/json' \
  -d '{
  "title": "beam"
}'

Then I can get the update_mask value from the server side, and use the update_mask value to do partial update in SQL.

But when I do the same with Kratos HTTP Server, I can only get the UpdateMask field to be nil .

So, my question: Do Kratos support this patch feature as gRPC-Gateway?
If so, how can I use it?
If not, does Kratos plan to support it in the future?

[dosubot]

Hi @RyoJerryYu! I'm Dosu and I’m helping the kratos team.

Kratos does not support automatic population of the FieldMask (update_mask) for PATCH requests like gRPC-Gateway does. In Kratos, the FieldMask will be nil unless you manually set it in your handler logic. There are no current plans to add this feature, and it's not mentioned in the roadmap or documentation.

If you need similar behavior, you'll have to manually extract which fields are present in the request body and populate the FieldMask yourself in your handler. For reference, see the gRPC-Gateway patch feature explanation and Kratos's form decoding code, which shows FieldMask support for query/form values but not for automatic PATCH body extraction.

Keep an eye on the Kratos roadmap or community discussions for any future updates, but currently, manual handling is required.

To reply, just mention @dosu.

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