Fixed #29750 -- Added View.setup() hook for class-based views.

docs/ref/class-based-views/base.txt

@@ -24,6 +24,7 @@ MRO is an acronym for Method Resolution Order.
 
     **Method Flowchart**
 
+    #. :meth:`setup()`
     #. :meth:`dispatch()`
     #. :meth:`http_method_not_allowed()`
     #. :meth:`options()`
@@ -70,11 +71,22 @@ MRO is an acronym for Method Resolution Order.
         attributes.
 
         When the view is called during the request/response cycle, the
-        :class:`~django.http.HttpRequest` is assigned to the view's ``request``
-        attribute. Any positional and/or keyword arguments :ref:`captured from
-        the URL pattern <how-django-processes-a-request>` are assigned to the
-        ``args`` and ``kwargs`` attributes, respectively. Then :meth:`dispatch`
-        is called.
+        :meth:`setup` method assigns the :class:`~django.http.HttpRequest` to
+        the view's ``request`` attribute, and any positional and/or keyword
+        arguments :ref:`captured from the URL pattern
+        <how-django-processes-a-request>` to the ``args`` and ``kwargs``
+        attributes, respectively. Then :meth:`dispatch` is called.
+
+    .. method:: setup(request, *args, **kwargs)
+
+        .. versionadded:: 2.2
+
+        Initializes view instance attributes: ``self.request``, ``self.args``,
+        and ``self.kwargs`` prior to :meth:`dispatch`.
+
+        Overriding this method allows mixins to setup instance attributes for
+        reuse in child classes. When overriding this method, you must call
+        ``super()``.
 
     .. method:: dispatch(request, *args, **kwargs)
 
@@ -123,6 +135,7 @@ MRO is an acronym for Method Resolution Order.
 
     **Method Flowchart**
 
+    #. :meth:`~django.views.generic.base.View.setup()`
     #. :meth:`~django.views.generic.base.View.dispatch()`
     #. :meth:`~django.views.generic.base.View.http_method_not_allowed()`
     #. :meth:`~django.views.generic.base.ContextMixin.get_context_data()`
@@ -184,6 +197,7 @@ MRO is an acronym for Method Resolution Order.
 
     **Method Flowchart**
 
+    #. :meth:`~django.views.generic.base.View.setup()`
     #. :meth:`~django.views.generic.base.View.dispatch()`
     #. :meth:`~django.views.generic.base.View.http_method_not_allowed()`
     #. :meth:`get_redirect_url()`

docs/ref/class-based-views/flattened-index.txt

@@ -31,6 +31,7 @@ Simple generic views
 * :meth:`~django.views.generic.base.View.dispatch`
 * ``head()``
 * :meth:`~django.views.generic.base.View.http_method_not_allowed`
+* :meth:`~django.views.generic.base.View.setup`
 
 ``TemplateView``
 ----------------
@@ -55,6 +56,7 @@ Simple generic views
 * ``head()``
 * :meth:`~django.views.generic.base.View.http_method_not_allowed`
 * :meth:`~django.views.generic.base.TemplateResponseMixin.render_to_response`
+* :meth:`~django.views.generic.base.View.setup`
 
 ``RedirectView``
 ----------------
@@ -80,6 +82,7 @@ Simple generic views
 * ``options()``
 * ``post()``
 * ``put()``
+* :meth:`~django.views.generic.base.View.setup`
 
 Detail Views
 ============
@@ -116,6 +119,7 @@ Detail Views
 * ``head()``
 * :meth:`~django.views.generic.base.View.http_method_not_allowed`
 * :meth:`~django.views.generic.base.TemplateResponseMixin.render_to_response`
+* :meth:`~django.views.generic.base.View.setup`
 
 List Views
 ==========
@@ -154,6 +158,7 @@ List Views
 * :meth:`~django.views.generic.base.View.http_method_not_allowed`
 * :meth:`~django.views.generic.list.MultipleObjectMixin.paginate_queryset`
 * :meth:`~django.views.generic.base.TemplateResponseMixin.render_to_response`
+* :meth:`~django.views.generic.base.View.setup`
 
 Editing views
 =============
@@ -189,6 +194,7 @@ Editing views
 * :meth:`~django.views.generic.base.View.http_method_not_allowed`
 * :meth:`~django.views.generic.edit.ProcessFormView.post`
 * :meth:`~django.views.generic.edit.ProcessFormView.put`
+* :meth:`~django.views.generic.base.View.setup`
 
 ``CreateView``
 --------------
@@ -233,6 +239,7 @@ Editing views
 * :meth:`~django.views.generic.edit.ProcessFormView.post`
 * ``put()``
 * :meth:`~django.views.generic.base.TemplateResponseMixin.render_to_response`
+* :meth:`~django.views.generic.base.View.setup`
 
 ``UpdateView``
 --------------
@@ -277,6 +284,7 @@ Editing views
 * :meth:`~django.views.generic.edit.ProcessFormView.post`
 * ``put()``
 * :meth:`~django.views.generic.base.TemplateResponseMixin.render_to_response`
+* :meth:`~django.views.generic.base.View.setup`
 
 ``DeleteView``
 --------------
@@ -313,6 +321,7 @@ Editing views
 * :meth:`~django.views.generic.base.View.http_method_not_allowed`
 * ``post()``
 * :meth:`~django.views.generic.base.TemplateResponseMixin.render_to_response`
+* :meth:`~django.views.generic.base.View.setup`
 
 Date-based views
 ================
@@ -356,6 +365,7 @@ Date-based views
 * :meth:`~django.views.generic.base.View.http_method_not_allowed`
 * :meth:`~django.views.generic.list.MultipleObjectMixin.paginate_queryset`
 * :meth:`~django.views.generic.base.TemplateResponseMixin.render_to_response`
+* :meth:`~django.views.generic.base.View.setup`
 
 ``YearArchiveView``
 -------------------
@@ -399,6 +409,7 @@ Date-based views
 * :meth:`~django.views.generic.base.View.http_method_not_allowed`
 * :meth:`~django.views.generic.list.MultipleObjectMixin.paginate_queryset`
 * :meth:`~django.views.generic.base.TemplateResponseMixin.render_to_response`
+* :meth:`~django.views.generic.base.View.setup`
 
 ``MonthArchiveView``
 --------------------
@@ -445,6 +456,7 @@ Date-based views
 * :meth:`~django.views.generic.base.View.http_method_not_allowed`
 * :meth:`~django.views.generic.list.MultipleObjectMixin.paginate_queryset`
 * :meth:`~django.views.generic.base.TemplateResponseMixin.render_to_response`
+* :meth:`~django.views.generic.base.View.setup`
 
 ``WeekArchiveView``
 -------------------
@@ -489,6 +501,7 @@ Date-based views
 * :meth:`~django.views.generic.base.View.http_method_not_allowed`
 * :meth:`~django.views.generic.list.MultipleObjectMixin.paginate_queryset`
 * :meth:`~django.views.generic.base.TemplateResponseMixin.render_to_response`
+* :meth:`~django.views.generic.base.View.setup`
 
 ``DayArchiveView``
 ------------------
@@ -539,6 +552,7 @@ Date-based views
 * :meth:`~django.views.generic.base.View.http_method_not_allowed`
 * :meth:`~django.views.generic.list.MultipleObjectMixin.paginate_queryset`
 * :meth:`~django.views.generic.base.TemplateResponseMixin.render_to_response`
+* :meth:`~django.views.generic.base.View.setup`
 
 ``TodayArchiveView``
 --------------------
@@ -589,6 +603,7 @@ Date-based views
 * :meth:`~django.views.generic.base.View.http_method_not_allowed`
 * :meth:`~django.views.generic.list.MultipleObjectMixin.paginate_queryset`
 * :meth:`~django.views.generic.base.TemplateResponseMixin.render_to_response`
+* :meth:`~django.views.generic.base.View.setup`
 
 ``DateDetailView``
 ------------------
@@ -634,3 +649,4 @@ Date-based views
 * ``head()``
 * :meth:`~django.views.generic.base.View.http_method_not_allowed`
 * :meth:`~django.views.generic.base.TemplateResponseMixin.render_to_response`
+* :meth:`~django.views.generic.base.View.setup`

docs/ref/class-based-views/generic-display.txt

@@ -25,6 +25,7 @@ many projects they are typically the most commonly used views.
 
     **Method Flowchart**
 
+    #. :meth:`~django.views.generic.base.View.setup()`
     #. :meth:`~django.views.generic.base.View.dispatch()`
     #. :meth:`~django.views.generic.base.View.http_method_not_allowed()`
     #. :meth:`~django.views.generic.base.TemplateResponseMixin.get_template_names()`
@@ -95,6 +96,7 @@ many projects they are typically the most commonly used views.
 
     **Method Flowchart**
 
+    #. :meth:`~django.views.generic.base.View.setup()`
     #. :meth:`~django.views.generic.base.View.dispatch()`
     #. :meth:`~django.views.generic.base.View.http_method_not_allowed()`
     #. :meth:`~django.views.generic.base.TemplateResponseMixin.get_template_names()`