Protobuf: Enum values not defined in enum class

[plannigan]

The documentation for enum says:

For example, you can access the values in the three following ways for the following enum in a proto:

enum SomeEnum {
    VALUE_A = 0;
    VALUE_B = 5;
    VALUE_C = 1234;
}

value-a = myproto_pb2.SomeEnum.VALUE_A
# or
myproto_pb2.VALUE_A
# or
myproto_pb2.SomeEnum.Value('VALUE_A')

But value-a = myproto_pb2.SomeEnum.VALUE_A fails.

What version of protobuf and what language are you using?
Version: v3.7.1/v3.6.1
Language: Python

What operating system (Linux, Windows, ...) and version?
Xubuntu 18.04

What runtime / compiler are you using (e.g., python version or gcc version)
gcc

What did you do?

1. Save the proto definition from the documentation to a file name myproto.proto.
2. Generate the python code:

./protoc --python_out=. --proto_path=. myproto.proto 

1. Attempt to access the value in the ways the documentation demonstrates.

python -c "import myproto_pb2; print(myproto_pb2.SomeEnum.Value('VALUE_A')); print(myproto_pb2.VALUE_A); print(myproto_pb2.SomeEnum.VALUE_A);"

What did you expect to see

0
0

What did you see instead?

0
Traceback (most recent call last):
  File "<string>", line 1, in <module>
AttributeError: 'EnumTypeWrapper' object has no attribute 'VALUE_A'

[anandolee]

Oh, we updated the document earlier than it should be. The __getattr__ is added in this PR which is not release in v3.7.1:
https://github.com/protocolbuffers/protobuf/commit/0de6577b7d5702a133f0eade4ddf6b94893e975a#diff-abebaaaa517a7cbc213cb3d39c6e444b

[pkalebu]

what's the correct way to get the value of an enum then?

[markisus]

@pkalebu It looks like you have to do myproto_pb2.SomeEnum.Value('VALUE_A')

[timgrossmann]

@markisus Thanks for this, looks like the documentation needs quite some updates to conform to Proto3 😅

Would've needed to read the actual commit changes to get the answer to read the enum values.
Unfortunately due to this changes, even the most downloaded VS-Code plugin will show errors for valid code...

Do they have their documentation source open?
I think I'd be able to update some of it since I'm writing a blog post about it anyway 😄