load_proto.py

'''
I was playing around with dynamically compiling and loading protobuf files. This kind of works,
so I wanted to save it for later.

I guess what I would want it to do is create a container object representing the message and enum
descriptors that allows you to access them as normal attributes.

Alternatively you can have protoc output a .py file and then fuss around with importlib to load it.
'''


import os
import subprocess
import tempfile

from google.protobuf.descriptor import MakeDescriptor
from google.protobuf.descriptor_pb2 import FileDescriptorSet
from google.protobuf.reflection import MakeClass

def compile_proto(proto):
  with tempfile.NamedTemporaryFile(mode='w') as infile:
    with tempfile.NamedTemporaryFile(mode='rb') as outfile:
      infile.write(proto)
      infile.flush()
      subprocess.check_call(['protoc', '-o', outfile.name,
        '--proto_path', os.path.dirname(infile.name), infile.name])
      return outfile.read()

proto = compile_proto('''
  syntax = "proto2";
  message Foo { }
''')
fds = FileDescriptorSet.FromString(proto)
file_descriptor = fds.file
msg_descriptor = MakeDescriptor(file_descriptor[0].message_type[0])
msg_class = MakeClass(msg_descriptor)
msg = msg_class()

print(msg)