BUG: stop designer from setting line-edits in ui file to be readOnly when PYDM_DESIGNER_ONLINE enabled

when editing a lineedit widget in designer after doing 'export PYDM_DESIGNER_ONLINE=1',
we want widgets to act as read-only so PVs are not accidentally changed
when modifying screens. this is enforced by the dataplugins themselves
and is_read_only() (set during designer setup: https://github.com/slaclab/pydm/blob/master/pydm/qtdesigner.py#L47)

but we don't want the readOnly=true status to be saved into the
ui file containing the lineedit.

to avoid this, don't let lineedit set itself to readOnly if it's
loaded in designer with live data enabled. (it will still act in a
read-only way thanks to dataplugins themselves)

Author: nstelter-slac

pydm/widgets/line_edit.py

@@ -10,7 +10,7 @@
 from .base import PyDMWritableWidget, TextFormatter, str_types, PostParentClassInitSetup
 from pydm import utilities
 from .display_format import DisplayFormat, parse_value_for_display
-from pydm.utilities import ACTIVE_QT_WRAPPER, QtWrapperTypes
+from pydm.utilities import ACTIVE_QT_WRAPPER, QtWrapperTypes, is_qt_designer
 
 logger = logging.getLogger(__name__)
 
@@ -162,14 +162,26 @@ def send_value(self):
 
     def setReadOnly(self, readOnly):
         self._user_set_read_only = readOnly
-        super().setReadOnly(True if self._user_set_read_only else not self._write_access)
+        shouldSetReadOnly = True if self._user_set_read_only else (not self._write_access)
+        # When in designer and reading in live data (DESIGNER_ONLINE), don't set and therefore save to
+        # the ui file readOnly=True setting. While we do want widgets to act in read-only way in designer
+        # (so don't accidentally write data during editing), this is handled in the data_plugins themselves.
+        if is_qt_designer() and config.DESIGNER_ONLINE:
+            shouldSetReadOnly = False
+        super().setReadOnly(shouldSetReadOnly)
 
     def write_access_changed(self, new_write_access):
         """
         Change the PyDMLineEdit to read only if write access is denied
         """
         super().write_access_changed(new_write_access)
         if not self._user_set_read_only:
+            shouldSetReadOnly = not new_write_access
+            # When in designer and reading in live data (DESIGNER_ONLINE), don't set and therefore save to
+            # the ui file readOnly=True setting. While we do want widgets to act in read-only way in designer
+            # (so don't accidentally write data during editing), this is handled in the data_plugins themselves.
+            if is_qt_designer() and config.DESIGNER_ONLINE:
+                shouldSetReadOnly = False
             super().setReadOnly(not new_write_access)
 
     def unit_changed(self, new_unit):