Unrecognized method, property, or field for generated protobuf message

Hi all,

We have a project where we communicate with a device using gRPC. On the computer, we run Python in a virtual enviornment. We load that environment in matlab using pyenv. We use MATLAB 2023b (23.2.0.2599560 (R2023b) Update 8) and Python 3.10.11.

Connecting with the device and querying some device information works in both, Python and MATLAB. However, since 2-3 months, we are unable to access members of protobuf messages. Below is an example of the code we execute in Python and the equivalent code executed in MATLAB:

Python:

% C:\work\data\kingfisher-py\.venv\Scripts\python.exe "..."
import kingfisher_py.lib as kgfLib
scn = kgfLib.device.Scanner('10.10.1.1', '8081')
device_info = scn.device_info.get_info()
device_info.sw_rev
items {
  key: "mcu"
  value: "v1.0.1"
}

Invalid expression. When calling a function or indexing a variable, use parentheses. Otherwise, check for mismatched delimiters.

items {
  key: "kingfisher"
  value: "5.2.0-cam-cal-third-party-rc.1-5-gd6f7161"
}
% response continues...

MATLAB:

>> kgfLib = py.importlib.import_module('kingfisher_py.lib');
>> scn = kgfLib.device.Scanner('10.10.1.1', '8081');
>> deviceInfo = scn.device_info.get_info();
>> deviceInfo.HasField('sw_rev')

ans =

  logical

   1

>> deviceInfo.sw_rev
Unrecognized method, property, or field 'sw_rev' for class 'py.kf.api.messages.system_pb2.GetDeviceInfoResponse'.
 
>> deviceInfo

deviceInfo = 

  Python GetDeviceInfoResponse with properties:

    DESCRIPTOR: [1×1 py.google._upb._message.Descriptor]

    manufact_rev {
      device_name: "BLK360-2060047"
      serial_number: "2060047"
    }
    sw_rev {
      items {
        key: "mcu"
        value: "v1.0.1"
      }
      items {
        key: "kingfisher"
        value: "5.2.0-cam-cal-third-party-rc.1-5-gd6f7161"
      }
    % response continues...

Note that the same virtual environment is active. MATLAB even says that the field sw_rev exists, but still cannot access it. Also, we checked different versions and combinations of MATLAB and Python. Specifically:

• Matlab 9.10.0.2198249 (R2021a) Update 8 + Python 3.8.10
• Matlab 9.13.0.2193358 (R2022b) Update 5 + Python 3.8.10
• Matlab 9.13.0.2193358 (R2022b) Update 5 + Python 3.10.11
• Matlab 23.2.0.2599560 (R2023b) Update 8 + Python 3.10.11

The behaviour is the same with all versions. As the whole communication with the device is set up using protobuf, there is not much we can do with the device at this point as we run into this problem all accorss our MATLAB code base.

Is this a known issue, e.g. with a newer protobuf version? As mentioned, we did not have any issues like this until 2-3 months ago.

Hope to get some help or at least an explanation. Thank you :-)

[Joel Buesser]

Update: It is dependent on the protobuf version.

• protobuf 3.20.1 works
• protobuf 4.25.2 doesn't work
• protobuf 5.27.1 doens't work

Answer 1

[Joel Buesser]

I reached out to Customer Support (thank you for the quick assistance!).

It is a bug that for some new versions of libraries, properties/methods cannot be called anymore using library.method although the method is found when searched for.

As a workaround, I downgraded to protobuf 3.20.1 in my case. Alternatively, the property above could be accessed using py.getattr(deviceInfo, 'sw_rev').