json_marshaler.go

// Licensed to the Apache Software Foundation (ASF) under one or more
// contributor license agreements.  See the NOTICE file distributed with
// this work for additional information regarding copyright ownership.
// The ASF licenses this file to You under the Apache License, Version 2.0
// (the "License"); you may not use this file except in compliance with
// the License.  You may obtain a copy of the License at
//
//     http://www.apache.org/licenses/LICENSE-2.0
//
// Unless required by applicable law or agreed to in writing, software
// distributed under the License is distributed on an "AS IS" BASIS,
// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
// See the License for the specific language governing permissions and
// limitations under the License.

package protoencoding

import (
	"bytes"
	"encoding/json"
)

import (
	"google.golang.org/protobuf/encoding/protojson"

	"google.golang.org/protobuf/proto"
)

type jsonMarshaler struct {
	resolver        Resolver
	indent          string
	useProtoNames   bool
	emitUnpopulated bool
}

func newJSONMarshaler(resolver Resolver, options ...JSONMarshalerOption) Marshaler {
	jsonMarshaler := &jsonMarshaler{
		resolver: resolver,
	}
	for _, option := range options {
		option(jsonMarshaler)
	}
	return jsonMarshaler
}

func (m *jsonMarshaler) Marshal(message proto.Message) ([]byte, error) {
	if err := ReparseUnrecognized(m.resolver, message.ProtoReflect()); err != nil {
		return nil, err
	}
	options := protojson.MarshalOptions{
		Resolver:        m.resolver,
		UseProtoNames:   m.useProtoNames,
		EmitUnpopulated: m.emitUnpopulated,
	}
	data, err := options.Marshal(message)
	if err != nil {
		return nil, err
	}
	// This is needed due to the instability of protojson output.
	//
	// https://github.com/golang/protobuf/issues/1121
	// https://go-review.googlesource.com/c/protobuf/+/151340
	// https://developers.google.com/protocol-buffers/docs/reference/go/faq#unstable-json
	//
	// We may need to do a full encoding/json encode/decode in the future if protojson
	// produces non-deterministic output.
	buffer := bytes.NewBuffer(nil)
	if m.indent != "" {
		if err := json.Indent(buffer, data, "", m.indent); err != nil {
			return nil, err
		}
	} else {
		if err := json.Compact(buffer, data); err != nil {
			return nil, err
		}
	}
	return buffer.Bytes(), nil
}