oneof inside nested message

[Adrian Schlatter]

Hi,

I am facing a problem with oneof {} inside a nested message and Python 3.7 (not sure whether it is limited to Python 3.7 or even to Python in general). Example:

demo.proto

syntax = "proto3";

package oneofInsideNestedMessage;

message outside {
    message inside {
        oneof dummyName {
                MsgA a = 1;
                MsgB b = 2;
        }
    }
}

message MsgA {
        string text = 1;
}

message MsgB {
        uint32 number = 1;
}

demo.py:

from demo_pb2 import outside

msg = outside()
msg.inside.a.text = 'test'

Result:

I expect that this will

a) choose MsgA as type for the oneof {

b) set text field to 'test'

What actually happens:

Traceback (most recent call last):

  File "<ipython-input-6-da73825bef90>", line 1, in <module>
    runfile('.../demo.py', wdir='...')

  File "...\site-packages\spyder_kernels\customize\spydercustomize.py", line 827, in runfile
    execfile(filename, namespace)

  File "...\site-packages\spyder_kernels\customize\spydercustomize.py", line 110, in execfile
    exec(compile(f.read(), filename, 'exec'), namespace)

  File ".../demo.py", line 11, in <module>
    msg.inside.a.text = 'test'

AttributeError: '_FieldProperty' object has no attribute 'text'

It does not happen when oneof is located in "outside" only when in "inside". As I want to switch an existing format to protobuf I do not want to change the structure of the data as this would break existing application code. Is this considered a bug (i.e., will go away eventually) or is this a limitation that will remain?

Best regards and thanks for making protobuf available publicly,

Adrian