Error compiling generated code with third party imports

[gmather]

Hello,

I was looking to experiment with this and ran into the following error:

type *"google.golang.org/genproto/googleapis/rpc/status".Status has no field or method MarshalToSizedBufferVT

The protobuf files that are complaining import files like:

import "google/rpc/status.proto";

with messages that look like:

message TestMessage {
   google.rpc.Status status = 2;
}

The google/rpc/status.proto file is copied locally for the code generation, but the generated code is importing the Go module from google.golang.org/genproto/googleapis/rpc/status so it's not part of the vtproto generation steps.

Is this an issue that you've had to resolve or any suggestions on how to approach this?

[vmg]

Hiii @gmather! This is indeed a real issue. Right now the check for foreign imports is really naive:

vtprotobuf/features/marshal/marshalto.go

Line 629 in 6ae7946

foreign := strings.HasPrefix(string(message.Desc.FullName()), "google.protobuf.")

I need to come up with a better way to perform this check. Let me think it through.

[elvizlai]

The related issue:
x.proto

syntax = "proto3";

package api.common;

option go_package          = "api/common";

import public "google/api/field_behavior.proto";
import public "google/api/httpbody.proto";
import public "google/protobuf/any.proto";
import public "google/protobuf/empty.proto";
import public "google/protobuf/field_mask.proto";
import public "google/protobuf/struct.proto";
import public "google/protobuf/timestamp.proto";
import public "google/protobuf/wrappers.proto";

message X {
}

The generated code has error: v.SizeVT undefined (type *structpb.Value has no field or method SizeVT)

[alexism]

@vmg
I ran into that issue as well.
For the "foreign" test, instead of relying on the message full name, could we instead test the interfaces implemented by the messages? Similarly to what the gRPC codec does.

The test would be performed before invoking any *VT functions.

For example, for the "unmarshal" feature, the generated code could be something like:

			if o, ok := interface{}(m.MY_FIELD).(interface{
				UnmarshalVT([]byte) error
			});ok{
				if err := o.UnmarshalVT(dAtA[iNdEx:postIndex]); err != nil {
					return err
				}
			}else{
				if err := proto.Unmarshal(dAtA[iNdEx:postIndex], m.MY_FIELD); err!=nil{
					return err
				}
			}

[vmg]

I like that suggestion! I've implemented it in #7 -- can you guys give this a go and see if it works in your codebases?