Resolve review comments: add some comments to clarify some confusion …

…script or code

Signed-off-by: Benjamin Wang <[email protected]>

scripts/genproto.sh

@@ -120,13 +120,35 @@ done
 # We only upgraded grpc-gateway from v1 to v2, but keep gogo/protobuf as it's for now.
 # So we have to convert v1 message to v2 message. Once we get rid of gogo/protobuf, and
 # start to depend on protobuf v2, then we can remove this patch.
+#
+# TODO(https://github.com/etcd-io/etcd/issues/14533): Remove the patch below after removal of gogo/protobuf
 for pb in api/etcdserverpb/rpc server/etcdserver/api/v3lock/v3lockpb/v3lock server/etcdserver/api/v3election/v3electionpb/v3election; do
   gwfile="$(dirname ${pb})/gw/$(basename ${pb}).pb.gw.go"
 
+  # Changes something like below,
+  #  import (
+  # +       protov1 "github.com/golang/protobuf/proto"
+  # +
   run sed -i -E "s|import \(|import \(\n\tprotov1 \"github.com/golang/protobuf/proto\"\n|g" "${gwfile}"
+
+  # Changes something like below,
+  # - return msg, metadata, err
+  # + return protov1.MessageV2(msg), metadata, err
   run sed -i -E "s|return msg, metadata, err|return protov1.MessageV2\(msg\), metadata, err|g" "${gwfile}"
+
+  # Changes something like below,
+  # - if err := marshaler.NewDecoder(newReader()).Decode(&protoReq); err != nil && err != io.EOF {
+  # + if err := marshaler.NewDecoder(newReader()).Decode(protov1.MessageV2(&protoReq)); err != nil && err != io.EOF {
   run sed -i -E "s|Decode\(\&protoReq\)|Decode\(protov1\.MessageV2\(\&protoReq\)\)|g" "${gwfile}"
+
+  # Changes something like below,
+  # - forward_Lease_LeaseKeepAlive_0(annotatedContext, mux, outboundMarshaler, w, req, func() (proto.Message, error) { return resp.Recv() }, mux.GetForwardResponseOptions()...)
+  # + forward_Lease_LeaseKeepAlive_0(annotatedContext, mux, outboundMarshaler, w, req, func() (proto.Message, error) {
+  # +   m1, err := resp.Recv()
+  # +   return protov1.MessageV2(m1), err
+  # + }, mux.GetForwardResponseOptions()...)
   run sed -i -E "s|return resp.Recv\(\)|\n\t\t\tm1, err := resp.Recv\(\)\n\t\t\treturn protov1.MessageV2\(m1\), err\n\t\t|g" "${gwfile}"
+
   run go fmt "${gwfile}"
 done
 

server/embed/serve.go

@@ -303,6 +303,7 @@ func (sctx *serveCtx) registerGateway(dial func(ctx context.Context) (*grpc.Clie
 		return nil, err
 	}
 
+	// Refer to https://grpc-ecosystem.github.io/grpc-gateway/docs/mapping/customizing_your_gateway/
 	gwmux := gw.NewServeMux(
 		gw.WithMarshalerOption(gw.MIMEWildcard,
 			&gw.HTTPBodyMarshaler{