DictFeatWidget fails to initialize when keys are not explicitly set

[thibaudruelle]

Context: I ran start_test_app on an instance of a custom driver which contained DictFeats initialized without specifying a keys=() argument. The following error shows up:

Traceback (most recent call last):
  File "C:\Anaconda3\lib\site-packages\lantz\ui\widgets.py", line 528, in __init__
    feat_widget = LabeledFeatWidget(self, target, feat)
  File "C:\Anaconda3\lib\site-packages\lantz\ui\widgets.py", line 415, in __init__
    self._widget = DictFeatWidget(parent, target, feat)
  File "C:\Anaconda3\lib\site-packages\lantz\ui\widgets.py", line 340, in __init__
    wid.feat_key = self._keys[0]
AttributeError: 'DictFeatWidget' object has no attribute '_keys'

Probable origin: In that case, keys default to None so when the DictFeatWidget is created by start_test_app the _keys attribute is not set within the if feat.keys statement before wid.feat_key = self._keys[0] is run, leading to the error.

Probable fix: wid.feat_key = self._keys[0] should only be run when keys exist.

Proposed fix: rewrite DictFeatWidget.__init__ as

def __init__(self, parent, target, feat):
        super().__init__(parent)
        self._feat = feat

        layout = QtGui.QHBoxLayout(self)

        valwid = WidgetMixin.from_feat(feat)
        valwid.bind_feat(feat)
        valwid.lantz_target = target

        if feat.keys:
            keywid = QtGui.QComboBox()
            if isinstance(feat.keys, dict):
                self._keys = list(feat.keys.keys())
            else:
                self._keys = list(feat.keys)

            keywid .addItems([str(key) for key in self._keys])
            keywid .currentIndexChanged.connect(self._combobox_changed)

            valwid.feat_key = self._keys[0]
        else:
            keywid = QtGui.QLineEdit()
            keywid .textChanged.connect(self._lineedit_changed)

        layout.addWidget(keywid )
        self._key_widget = keywid 

        layout.addWidget(valwid )
        self._value_widget = valwid