Remove NotImplementedErrors from "virtual" methods

Raising a NotImplementedError in a method of a base class
makes it impossible to use super() with it and do multiple
inheritance properly. Those methods should instead simply
return some default "empty" value, so that the methods in
the subclasses can still call them, if that's where they
fall in the MRO.

Change-Id: I581391e87dc58f0f76adea3dbf90cef173d3daef
Closes-bug: 1278825

horizon/base.py

@@ -594,9 +594,7 @@ def can_access(self, context):
 
 
 class Workflow(object):
-    def __init__(*args, **kwargs):
-        raise NotImplementedError()
-
+    pass
 
 try:
     from django.utils.functional import empty  # noqa

horizon/tables/actions.py

@@ -503,8 +503,7 @@ def filter(self, table, data, filter_string):
         This method must be overridden by subclasses and return
         the filtered data.
         """
-        raise NotImplementedError("The filter method has not been "
-                                  "implemented by %s." % self.__class__)
+        return data
 
     def is_api_filter(self, filter_field):
         """Determine if the given filter field should be used as an
@@ -550,18 +549,15 @@ def get_fixed_buttons(self):
         * ``value``: Value returned when the button is clicked. This value is
           passed to ``filter()`` as ``filter_string``.
         """
-        raise NotImplementedError("The get_fixed_buttons method has "
-                                  "not been implemented by %s." %
-                                  self.__class__)
+        return []
 
     def categorize(self, table, images):
         """Override to separate images into categories.
 
         Return a dict with a key for the value of each fixed button,
         and a value that is a list of images in that category.
         """
-        raise NotImplementedError("The categorize method has not been "
-                                  "implemented by %s." % self.__class__)
+        return {}
 
 
 class BatchAction(Action):
@@ -670,8 +666,6 @@ def action(self, request, datum_id):
 
         Return values are discarded, errors raised are caught and logged.
         """
-        raise NotImplementedError('action() must be defined for %s'
-                                  % self.__class__.__name__)
 
     def update(self, request, datum):
         """Switches the action verbose name, if needed."""
@@ -792,7 +786,6 @@ def delete(self, request, obj_id):
 
         Override to provide delete functionality specific to your data.
         """
-        raise NotImplementedError("DeleteAction must define a delete method.")
 
     def get_default_classes(self):
         """Appends ``btn-danger`` to the action's default css classes.
@@ -821,8 +814,6 @@ def update_cell(self, request, datum, obj_id, cell_name, new_cell_value):
         This method must implements saving logic of the inline edited table
         cell.
         """
-        raise NotImplementedError(
-            "UpdateAction must define a update_cell method.")
 
     def allowed(self, request, datum, cell):
         """Determine whether updating is allowed for the current request.

horizon/tables/base.py

@@ -592,8 +592,7 @@ def get_data(self, request, obj_id):
         """Fetches the updated data for the row based on the object id
         passed in. Must be implemented by a subclass to allow AJAX updating.
         """
-        raise NotImplementedError("You must define a get_data method on %s"
-                                  % self.__class__.__name__)
+        return {}
 
 
 class Cell(html.HTMLElement):

horizon/tables/views.py

@@ -186,8 +186,7 @@ def _get_data_dict(self):
         return self._data
 
     def get_data(self):
-        raise NotImplementedError('You must define a "get_data" method on %s.'
-                                  % self.__class__.__name__)
+        return []
 
     def get_tables(self):
         if not self._tables:

horizon/tabs/base.py

@@ -355,12 +355,11 @@ def get_template_name(self, request):
                                  % self.__class__.__name__)
         return self.template_name
 
-    def get_context_data(self, request):
+    def get_context_data(self, request, **kwargs):
         """This method should return a dictionary of context data used to
         render the tab. Required.
         """
-        raise NotImplementedError("%s needs to define a get_context_data "
-                                  "method." % self.__class__.__name__)
+        return kwargs
 
     def enabled(self, request):
         """Determines whether or not the tab should be accessible
@@ -447,14 +446,14 @@ def load_table_data(self):
             # Mark our data as loaded so we don't run the loaders again.
             self._table_data_loaded = True
 
-    def get_context_data(self, request):
+    def get_context_data(self, request, **kwargs):
         """Adds a ``{{ table_name }}_table`` item to the context for each table
         in the :attr:`~horizon.tabs.TableTab.table_classes` attribute.
 
         If only one table class is provided, a shortcut ``table`` context
         variable is also added containing the single table.
         """
-        context = {}
+        context = super(TableTab, self).get_context_data(request, **kwargs)
         # If the data hasn't been manually loaded before now,
         # make certain it's loaded before setting the context.
         self.load_table_data()

horizon/utils/csvbase.py

@@ -94,8 +94,8 @@ def __init__(self, request, template, context, content_type, **kwargs):
         self.out.close()
 
     def get_row_data(self):
-        raise NotImplementedError("You must define a get_row_data method on %s"
-                                  % self.__class__.__name__)
+        return []
+
 
 if VERSION >= (1, 5, 0):
 
@@ -140,5 +140,4 @@ def get_content(self):
                 yield self.buffer()
 
         def get_row_data(self):
-            raise NotImplementedError("You must define a get_row_data method "
-                                      "on %s" % self.__class__.__name__)
+            return []

horizon/views.py

@@ -38,8 +38,7 @@ def get_data(self, request, context, *args, **kwargs):
         """This method should handle any necessary API calls, update the
         context object, and return the context object at the end.
         """
-        raise NotImplementedError("You must define a get_data method "
-                                   "on %s" % self.__class__.__name__)
+        return context
 
     def get(self, request, *args, **kwargs):
         context = self.get_context_data(**kwargs)

openstack_dashboard/usage/base.py

@@ -191,7 +191,7 @@ def get_limits(self):
         self.get_cinder_limits()
 
     def get_usage_list(self, start, end):
-        raise NotImplementedError("You must define a get_usage_list method.")
+        return []
 
     def summarize(self, start, end):
         if not api.nova.extension_supported('SimpleTenantUsage', self.request):