Simplify mode-checking in command.

Rather than maintaining separate _modes and _not_modes lists, just
build a single _modes list in the constructor.

qutebrowser/commands/command.py

@@ -82,7 +82,6 @@ class Command:
         no_replace_variables: Don't replace variables like {url}
         _qute_args: The saved data from @cmdutils.argument
         _modes: The modes the command can be executed in.
-        _not_modes: The modes the command can not be executed in.
         _count: The count set for the command.
         _instance: The object to bind 'self' to.
         _scope: The scope to get _instance for in the object registry.
@@ -101,10 +100,14 @@ class Command:
             for m in modes:
                 if not isinstance(m, usertypes.KeyMode):
                     raise TypeError("Mode {} is no KeyMode member!".format(m))
-        if not_modes is not None:
+            self._modes = modes
+        elif not_modes is not None:
             for m in not_modes:
                 if not isinstance(m, usertypes.KeyMode):
                     raise TypeError("Mode {} is no KeyMode member!".format(m))
+            self._modes = [m for m in usertypes.KeyMode if m not in not_modes]
+        else:
+            self._modes = list(usertypes.KeyMode)
         if scope != 'global' and instance is None:
             raise ValueError("Setting scope without setting instance makes "
                              "no sense!")
@@ -114,8 +117,6 @@ class Command:
         self.hide = hide
         self.deprecated = deprecated
         self._instance = instance
-        self._modes = modes
-        self._not_modes = not_modes
         self._scope = scope
         self._star_args_optional = star_args_optional
         self.debug = debug
@@ -155,17 +156,7 @@ class Command:
         """
         mode_manager = objreg.get('mode-manager', scope='window',
                                   window=win_id)
-        curmode = mode_manager.mode
-        if self._modes is not None and curmode not in self._modes:
-            mode_names = '/'.join(mode.name for mode in self._modes)
-            raise cmdexc.PrerequisitesError(
-                "{}: This command is only allowed in {} mode.".format(
-                    self.name, mode_names))
-        elif self._not_modes is not None and curmode in self._not_modes:
-            mode_names = '/'.join(mode.name for mode in self._not_modes)
-            raise cmdexc.PrerequisitesError(
-                "{}: This command is not allowed in {} mode.".format(
-                    self.name, mode_names))
+        self.validate_mode(mode_manager.mode)
 
         used_backend = usertypes.arg2backend[objreg.get('args').backend]
         if self.backend is not None and used_backend != self.backend:
@@ -525,3 +516,15 @@ class Command:
         log.commands.debug('Calling {}'.format(
             debug_utils.format_call(self.handler, posargs, kwargs)))
         self.handler(*posargs, **kwargs)
+
+    def validate_mode(self, mode):
+        """Raise cmdexc.PrerequisitesError unless allowed in the given mode.
+
+        Args:
+            mode: The usertypes.KeyMode to check.
+        """
+        if mode not in self._modes:
+            mode_names = '/'.join(m.name for m in self._modes)
+            raise cmdexc.PrerequisitesError(
+                "{}: This command is only allowed in {} mode, not {}.".format(
+                    self.name, mode_names, mode.name))

tests/end2end/features/hints.feature

@@ -2,7 +2,7 @@ Feature: Using hints
 
     Scenario: Using :follow-hint outside of hint mode (issue 1105)
         When I run :follow-hint
-        Then the error "follow-hint: This command is only allowed in hint mode." should be shown
+        Then the error "follow-hint: This command is only allowed in hint mode, not normal." should be shown
 
     Scenario: Using :follow-hint with an invalid index.
         When I open data/hints/html/simple.html

tests/end2end/features/misc.feature

@@ -589,7 +589,7 @@ Feature: Various utility commands.
         And I run :repeat-command with count 2
         And I wait until the scroll position changed to 0/0
         Then the page should not be scrolled
-        And the error "prompt-accept: This command is only allowed in prompt/yesno mode." should be shown
+        And the error "prompt-accept: This command is only allowed in prompt/yesno mode, not normal." should be shown
 
     @qtwebengine_createWindow
     Scenario: :repeat-command with mode-switching command

tests/end2end/test_insert_mode.py

@@ -93,7 +93,7 @@ def test_auto_leave_insert_mode(quteproc):
     quteproc.send_cmd(':paste-primary')
 
     expected_message = ('paste-primary: This command is only allowed in '
-                        'insert mode.')
+                        'insert mode, not caret.')
     quteproc.mark_expected(category='message',
                            loglevel=logging.ERROR,
                            message=expected_message)