use mro to collect methods

ignore methods attr unless explicitly set
add changelog

Author: davidism

CHANGES

@@ -24,8 +24,10 @@ Major release, unreleased
 - Add support for ``provide_automatic_options`` in ``add_url_rule`` to disable
   adding OPTIONS method when the ``view_func`` argument is not a class.
   (`#1489`_).
+- ``MethodView`` can inherit method handlers from base classes. (`#1936`_)
 
 .. _#1489: https://github.com/pallets/flask/pull/1489
+.. _#1936: https://github.com/pallets/flask/pull/1936
 .. _#2017: https://github.com/pallets/flask/pull/2017
 .. _#2223: https://github.com/pallets/flask/pull/2223
 

flask/views.py

@@ -102,38 +102,35 @@ def view(*args, **kwargs):
         return view
 
 
-def get_methods(cls):
-    return getattr(cls, 'methods', []) or []
-
-
 class MethodViewType(type):
+    """Metaclass for :class:`MethodView` that determines what methods the view
+    defines.
+    """
+
+    def __init__(cls, name, bases, d):
+        super(MethodViewType, cls).__init__(name, bases, d)
 
-    def __new__(cls, name, bases, d):
-        rv = type.__new__(cls, name, bases, d)
         if 'methods' not in d:
-            methods = set(m for b in bases for m in get_methods(b))
-            for key in d:
-                if key in http_method_funcs:
+            methods = set()
+
+            for key in http_method_funcs:
+                if hasattr(cls, key):
                     methods.add(key.upper())
-            # If we have no method at all in there we don't want to
-            # add a method list.  (This is for instance the case for
-            # the base class or another subclass of a base method view
-            # that does not introduce new methods).
+
+            # If we have no method at all in there we don't want to add a
+            # method list. This is for instance the case for the base class
+            # or another subclass of a base method view that does not introduce
+            # new methods.
             if methods:
-                rv.methods = sorted(methods)
-        return rv
+                cls.methods = methods
 
 
 class MethodView(with_metaclass(MethodViewType, View)):
-    """Like a regular class-based view but that dispatches requests to
-    particular methods.  For instance if you implement a method called
-    :meth:`get` it means it will respond to ``'GET'`` requests and
-    the :meth:`dispatch_request` implementation will automatically
-    forward your request to that.  Also :attr:`options` is set for you
-    automatically::
+    """A class-based view that dispatches request methods to the corresponding
+    class methods. For example, if you implement a ``get`` method, it will be
+    used to handle ``GET`` requests. ::
 
         class CounterAPI(MethodView):
-
             def get(self):
                 return session.get('counter', 0)
 
@@ -143,11 +140,14 @@ def post(self):
 
         app.add_url_rule('/counter', view_func=CounterAPI.as_view('counter'))
     """
+
     def dispatch_request(self, *args, **kwargs):
         meth = getattr(self, request.method.lower(), None)
+
         # If the request method is HEAD and we don't have a handler for it
         # retry with GET.
         if meth is None and request.method == 'HEAD':
             meth = getattr(self, 'get', None)
+
         assert meth is not None, 'Unimplemented method %r' % request.method
         return meth(*args, **kwargs)