I hit a roadblock trying to parse out a nested message. I have found a
workaround, but I'd like to get to the bottom of this.
I have a .proto file like this:
```syntax = "proto3";
import "google/protobuf/descriptor.proto";
import "google/protobuf/any.proto";
package Test2;
message Subscription {
google.protobuf.FileDescriptorSet descriptor_set = 1;
string name = 2;
int32 interval = 3;
}
message AnotherMsg {
google.protobuf.FileDescriptorSet descriptor_set = 1;
string test = 2;
}
enum msg_id {
UNSPECIFIED = 0;
SUBSCRIBE = 1;
}
message WSMessage{
msg_id req_id = 1;
google.protobuf.Any msg_body = 2;
google.protobuf.FileDescriptorSet descriptor_set = 3;
}
message WSReceivedMessage {
repeated WSMessage message = 1;
google.protobuf.FileDescriptorSet descriptor_set = 2;
}```
WSMessage has an ID, and a message. The documentation indicates
JsonStringToMessage "It will use the DescriptorPool
<https://developers.google.com/protocol-buffers/docs/reference/cpp/google.protobuf.descriptor#DescriptorPool>
of
the passed-in message to resolve Any types."
Now, I haven't been able to find any member data or member function of
Message that allows access to a DescriptorPool. I see access to
descriptors...
I even went down the rabbit hole of using the "Parser" with input from the
Tokenizer to read the descriptor.proto file:
```std::fstream myFile;
myFile.open("descriptor.proto");
google::protobuf::io::IstreamInputStream realFileInput(&myFile);
google::protobuf::io::IstreamInputStream* myFileInput = &realFileInput;
myCollector realCollector{};
myCollector* collector = &realCollector;
google::protobuf::io::Tokenizer myTkn(myFileInput, collector);
google::protobuf::compiler::Parser myParser{};
google::protobuf::FileDescriptorProto myProto;
myParser.Parse(&myTkn, &myProto);```
>From this parser, I obtained my FileDescriptorProto, which I then used in a
DescriptorPool:
```google::protobuf::DescriptorPool myPool{};
myPool.BuildFile(myProto);```
Next I tried to use the DynamicMessageFactory to create a message that
would contain the whole DescriptorPool of messages in my main .proto file.
This is where I hit the roadblock. There is no single descriptor, or
converter from a descriptor pool to a descriptor. The DynamicMessageFactory
creates a message from a single descriptor.
I can just simply declare a single message. My issue is I'm looking to have
a message with a descriptor pool (or some sort of descriptor) that contains
the possibilities for my "Any" message.
The documentation seems incorrect to me. util::Status
util::JsonStringToMessage(
StringPiece input,
Message
<https://developers.google.com/protocol-buffers/docs/reference/cpp/google.protobuf.message#Message>
*
message,
const JsonParseOptions
<https://developers.google.com/protocol-buffers/docs/reference/cpp/google.protobuf.util.json_util#JsonParseOptions>
&
options)
Converts from JSON to protobuf message.
This is a simple wrapper of JsonStringToBinary(). It will use the
DescriptorPool
<https://developers.google.com/protocol-buffers/docs/reference/cpp/google.protobuf.descriptor#DescriptorPool>
of
the passed-in message to resolve Any types.
There doesn't appear to be a "DescriptorPool" for a message. What am I
missing? Thanks very much for your help.
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