Sergei Trofimov be3c91b131 Device: raise RuntimeError in _check_ready ...

Previously, a AttributeError has been raised. This causes issues when
attempting to access some properties that rely on invoking commands on
the device. The error would get swallowed up in Python attribute
resolution machinery, resulting in an error claiming a missing
attribute.

For example, for AndroidDevice, "abi" is a property that internally
calls getprop(), which executes on the device, and thus requires a
connection. If attempting to access device.abi before device.connect()
has been invoked, the following sequence takes place

1. Caller tries to access attribute "abi" of device, which resolves to
   the device.abi property defined in the class.
2. device.abi calls device.getprop()
3. ...which calls device.execute()
4. ...which calls device._check_ready()
5. device._check_ready() raises AttributeError('device not ready.')
6. That gets propagated all the way up to 1., which gets interpreted
   as attribute not being found.
7. Since AndroidDevice defines a __getattr__(), that gets called next
8. __getattr__() looks for a loaded Device module that has an "abi"
   attribute. Since there isn't one, it raises AttributeError('abi').

The result is that the error reports a missing "abi" attribute, rather
than "device not ready", leading to some fun debugging.

Raising RuntimeError (which more appropriate for the circumstances
anyway) does not trigger __getattr__, so the correct error message is
reported to the user. The text of the message has also been adjusted to
make it clearer what has likely gone wrong.

2017-08-02 13:39:55 +01:00

..

__init__.py

Pylint fixes

2016-07-21 16:40:26 +01:00

device.py

Device: raise RuntimeError in _check_ready

2017-08-02 13:39:55 +01:00