Fix quick-complete highlighting quirk.

When the commandline reads ':open |', quick-completing the only offered
completion will set the commandline to ':open some_url |'. Since `open`
has `maxsplit=0`, everything after ':open' is (correctly) treated as
one argument. This means completion is opened again with 'some url '
as the pattern (note trailing whitespace), which makes the comletion
menu 'flicker' and stay open even though it was 'supposed' to quick
compelte.

This is fixed by ignoring the next completion request if we just
completed something after maxsplit (because we don't expect any more
completions after the last split).

Resolves #1519.

qutebrowser/completion/completer.py

@@ -198,15 +198,19 @@ class Completer(QObject):
         before, center, after = self._partition()
         log.completion.debug("Changing {} to '{}'".format(center, data))
         try:
-            needs_quoting = cmdutils.cmd_dict[before[0]].maxsplit is None
+            maxsplit = cmdutils.cmd_dict[before[0]].maxsplit
         except (KeyError, IndexError):
-            needs_quoting = True
-        if needs_quoting:
+            maxsplit = None
+        if maxsplit is None:
             data = self._quote(data)
         if model.count() == 1 and config.get('completion', 'quick-complete'):
             # If we only have one item, we want to apply it immediately
             # and go on to the next part.
             self._change_completed_part(data, before, after, immediate=True)
+            if maxsplit is not None and maxsplit < len(before):
+                # If we are quick-completing the part after maxsplit, don't
+                # keep offering completions (see issue #1519)
+                self._ignore_change = True
         else:
             log.completion.debug("Will ignore next completion update.")
             self._ignore_change = True

tests/unit/completion/test_completer.py

@@ -122,16 +122,12 @@ def cmdutils_patch(monkeypatch, stubs):
         """docstring."""
         pass
 
-    cmds = {
-        'set': set_command,
-        'help': show_help,
-        'open': openurl,
-        'bind': bind,
-        'tab-detach': tab_detach,
-    }
     cmd_utils = stubs.FakeCmdUtils({
-        name: command.Command(name=name, handler=fn)
-        for name, fn in cmds.items()
+        'set': command.Command(name='set', handler=set_command),
+        'help': command.Command(name='help', handler=show_help),
+        'open': command.Command(name='open', handler=openurl, maxsplit=0),
+        'bind': command.Command(name='bind', handler=bind),
+        'tab-detach': command.Command(name='tab-detach', handler=tab_detach),
     })
     monkeypatch.setattr('qutebrowser.completion.completer.cmdutils', cmd_utils)
 
@@ -264,3 +260,29 @@ def test_on_selection_changed(before, newtxt, after, completer_obj,
     if after_pos > len(after_txt):
         after_txt += ' '
     check(True, 1, after_txt, after_pos)
+
+def test_quickcomplete_flicker(status_command_stub, completer_obj,
+                               completion_widget_stub, config_stub):
+    """Validate fix for #1519: bookmark-load background highlighting quirk.
+
+    For commands like bookmark-load and open with maxsplit=0, a commandline
+    that looks like ':open someurl |' is considered to be completing the first
+    arg with pattern 'someurl ' (note trailing whitespace). As this matches the
+    one completion available, it keeps the completionmenu open.
+
+    This test validates that the completion model is not re-set after we
+    quick-complete an entry after maxsplit."""
+    model = unittest.mock.Mock()
+    model.data = unittest.mock.Mock(return_value='http://example.com')
+    indexes = [unittest.mock.Mock()]
+    selection = unittest.mock.Mock()
+    selection.indexes = unittest.mock.Mock(return_value=indexes)
+    completion_widget_stub.model.return_value = model
+
+    config_stub.data['completion']['quick-complete'] = True
+    model.count = unittest.mock.Mock(return_value=1)
+    _set_cmd_prompt(status_command_stub, ':open |')
+    completer_obj.on_selection_changed(selection)
+
+    completer_obj.schedule_completion_update()
+    assert not completion_widget_stub.set_model.called