Custom field options in Python

[Jan Koriťák]

Hello,

We would like to use Custom options for message fields in Python.

According to https://developers.google.com/protocol-buffers/docs/proto?hl=cs :

"As of this writing (version 2.0.3), custom options are not accessible in Python."

I would like to ask if there was any progress since then or can it be expected in near future ?

I have actually tried to use the custom options, and I could only get it working after hacking the generated Python file by moving the line with call to "RegisterExtension" right after  definition of the Extension field. So maybe we just need to tweak protoc a bit.

My test proto:

import "google/protobuf/descriptor.proto";

extend google.protobuf.FieldOptions {

  optional string comment = 50002;

}

message MyMessage {

  optional string foo = 1 [(comment) = "Not particularly useful field"];

}

Python console:

In [1]: import test_pb2

In [2]: test_pb2.MyMessage.DESCRIPTOR.fields[0].GetOptions().Extensions[test_pb2.comment]

Out[2]: u''

Hacked test_pb2.py:

...

COMMENT_FIELD_NUMBER = 50002

comment = descriptor.FieldDescriptor(

  name='comment', full_name='comment', index=0,

  number=50002, type=9, cpp_type=9, label=1,

  has_default_value=False, default_value=unicode("", "utf-8"),

  message_type=None, enum_type=None, containing_type=None,

  is_extension=True, extension_scope=None,

  options=None)

# MOVED FROM THE END OF FILE

google.protobuf.descriptor_pb2.FieldOptions.RegisterExtension(comment)

...

Python console:

In [1]: import test_pb2

In [2]: test_pb2.MyMessage.DESCRIPTOR.fields[0].GetOptions().Extensions[test_pb2.comment]

Out[2]: u'Not particularly useful field'

Best regards,

Jan Koriťák

[Jason Hsueh]

This has also been implemented internally and will be included in the next release.

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