raise...from info missing in DevFailed

[reszelaz]

I would like that the exception chain is propagated to the client.

I have the following device server:

from tango.server import Device, attribute


class DeviceRaiseFrom(Device):

    attr1 = attribute()

    def read_attr1(self):
        try:
            raise Exception("err1")
        except Exception as e:
            raise Exception("err2") from e


if __name__ == "__main__":
    DeviceRaiseFrom.run_server()

I run it in the following way:

tango_admin --add-server DeviceRaiseFrom/test DeviceRaiseFrom test/deviceraisefrom/1
python3 DeviceRaiseFrom.py test -v4

In itango3 I get:

In [1]: d = DeviceRaiseFrom('test/deviceraisefrom/1')

In [2]: d.attr1
PyDs_PythonError: Exception: err2

(For more detailed information type: tango_error)

In [3]: tango_error
Last tango error:
DevFailed[
DevError[
    desc = Exception: err2
           
  origin =   File "/home/zreszela/workspace/pytango/tango/server.py", line 132, in read_attr
    ret = worker.execute(read_method, self)
  File "/home/zreszela/workspace/pytango/tango/green.py", line 98, in execute
    return fn(*args, **kwargs)
  File "DeviceRaiseFrom.py", line 13, in read_attr1
    raise Exception("err2") from e

  reason = PyDs_PythonError
severity = ERR]

DevError[
    desc = Failed to read_attribute on device test/deviceraisefrom/1, attribute attr1
  origin = DeviceProxy::read_attribute()
  reason = API_AttributeFailed
severity = ERR]
]

In [4]:         try:
   ...:             raise Exception("err1")
   ...:         except Exception as e:
   ...:             raise Exception("err2") from e
   ...: 
Exception: err2
(For more detailed information type: python_error)

In [5]: 

In [5]: python_error
---------------------------------------------------------------------------
Exception                                 Traceback (most recent call last)
<ipython-input-4-055cdc174ea6> in <module>()
      1 try:
----> 2     raise Exception("err1")
      3 except Exception as e:

Exception: err1

The above exception was the direct cause of the following exception:

Exception                                 Traceback (most recent call last)
<ipython-input-4-055cdc174ea6> in <module>()
      2     raise Exception("err1")
      3 except Exception as e:
----> 4     raise Exception("err2") from e

Exception: err2

As you can see in PyTango the info about the original exception is lost.