How to cast descriptorpb.DescriptorProto to protoreflect.MessageDescriptor

[Eagleye126]

Hey all,
Im trying to create *dynamicpb.Message the following way:

import (
    "github.com/stretchr/testify/assert"
    "google.golang.org/protobuf/proto"
    "google.golang.org/protobuf/reflect/protoreflect"
    "google.golang.org/protobuf/types/descriptorpb"
    "google.golang.org/protobuf/types/dynamicpb"
    "testing"
)

func getDescriptorProto(fieldName string) protoreflect.MessageDescriptor {
    descProto := descriptorpb.DescriptorProto{
        Field: []*descriptorpb.FieldDescriptorProto{
            {
                Name: proto.String(fieldName),
                Type: descriptorpb.FieldDescriptorProto_TYPE_INT32.Enum(),
            },
        },
    }
    return descProto.ProtoReflect().Descriptor()
}

func getDynamicMessage(descriptor protoreflect.MessageDescriptor, value int32) *dynamicpb.Message {
    dynamicMessage := dynamicpb.NewMessage(descriptor)
    dynamicMessage.Set(dynamicMessage.Descriptor().Fields().ByName("id"), protoreflect.ValueOf(value))
    return dynamicMessage
}

var (
    idDescriptorProto = getDescriptorProto("id")
)

var (
    validIdMessage = getDynamicMessage(idDescriptorProto, int32(2))
)

Im getting this panic error:
runtime error: invalid memory address or nil pointer dereference

Seems like it triggers from dynamicMessage.Descriptor().Fields().ByName(...
And thats because descProto.ProtoReflect().Descriptor() will return the object without the fields I set.

Thank you for helping!

[Damien Neil]

descProto := descriptorpb.DescriptorProto{...}
return descProto.ProtoReflect().Descriptor()

This returns the descriptor of descProto, not the descriptor in descProto.

That is, it returns the descriptor for google.protobuf.DescriptorProto, which does not contain an id field.

You can use the google.golang.org/protobuf/reflect/protodesc package to convert a DescriptorProto to a protoreflect.MessageDescriptor.

[lfolger]

Closing for now. Please reopen the issue if you have further questions.