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// Copyright 2020-2024 Buf Technologies, Inc.
//
// Licensed 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 messageset
import (
"math"
"sync"
"google.golang.org/protobuf/proto"
"google.golang.org/protobuf/reflect/protodesc"
"google.golang.org/protobuf/types/descriptorpb"
)
var (
messageSetSupport bool
messageSetSupportInit sync.Once
)
// CanSupportMessageSets returns true if the protobuf-go runtime supports
// serializing messages with the message set wire format.
func CanSupportMessageSets() bool {
messageSetSupportInit.Do(func() {
// We check using the protodesc package, instead of just relying
// on protolegacy build tag, in case someone links in a fork of
// the protobuf-go runtime that supports legacy proto1 features
// or in case the protobuf-go runtime adds another mechanism to
// enable or disable it (such as environment variable).
_, err := protodesc.NewFile(&descriptorpb.FileDescriptorProto{
Name: proto.String("test.proto"),
MessageType: []*descriptorpb.DescriptorProto{
{
Name: proto.String("MessageSet"),
Options: &descriptorpb.MessageOptions{
MessageSetWireFormat: proto.Bool(true),
},
ExtensionRange: []*descriptorpb.DescriptorProto_ExtensionRange{
{
Start: proto.Int32(1),
End: proto.Int32(math.MaxInt32),
},
},
},
},
}, nil)
// When message sets are not supported, the above returns an error:
// message "MessageSet" is a MessageSet, which is a legacy proto1 feature that is no longer supported
messageSetSupport = err == nil
})
return messageSetSupport
}
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