PUT as create docs, and move mixin out to external gist

docs/api-guide/generic-views.md

@@ -368,6 +368,20 @@ If you are using a mixin across multiple views, you can take this a step further
 
 Using custom base classes is a good option if you have custom behavior that consistently needs to be repeated across a large number of views throughout your project.
 
+---
+
+# PUT as create
+
+Prior to version 3.0 the REST framework mixins treated `PUT` as either an update or a create operation, depending on if the object already existed or not.
+
+Allowing `PUT` as create operations is problematic, as it necessarily exposes information about the existence or non-existance of objects. It's also not obvious that transparently allowing re-creating of previously deleted instances is necessarily a better default behavior than simply returning `404` responses.
+
+Both styles "`PUT` as 404" and "`PUT` as create" can be valid in different circumstances, but from version 3.0 onwards we now use 404 behavior as the default, due to it being simpler and more obvious.
+
+If you need to generic PUT-as-create behavior you may want to include something like [this `AllowPUTAsCreateMixin` class](https://gist.github.com/tomchristie/a2ace4577eff2c603b1b) as a mixin to your views.
+
+---
+
 # Third party packages
 
 The following third party packages provide additional generic view implementations.

docs/topics/3.0-announcement.md

@@ -694,7 +694,7 @@ Allowing `PUT` as create operations is problematic, as it necessarily exposes in
 
 Both styles "`PUT` as 404" and "`PUT` as create" can be valid in different circumstances, but we've now opted for the 404 behavior as the default, due to it being simpler and more obvious.
 
-If you need to restore the previous behavior you can include the `AllowPUTAsCreateMixin` class in your view. This class can be imported from `rest_framework.mixins`.
+If you need to restore the previous behavior you may want to include [this `AllowPUTAsCreateMixin` class](https://gist.github.com/tomchristie/a2ace4577eff2c603b1b) as a mixin to your views.
 
 #### Customizing error responses.
 

rest_framework/mixins.py

@@ -6,10 +6,8 @@ which allows mixin classes to be composed in interesting ways.
 """
 from __future__ import unicode_literals
 
-from django.http import Http404
 from rest_framework import status
 from rest_framework.response import Response
-from rest_framework.request import clone_request
 from rest_framework.settings import api_settings
 
 
@@ -89,49 +87,3 @@ class DestroyModelMixin(object):
 
     def perform_destroy(self, instance):
         instance.delete()
-
-
-# The AllowPUTAsCreateMixin was previously the default behaviour
-# for PUT requests. This has now been removed and must be *explicitly*
-# included if it is the behavior that you want.
-# For more info see: ...
-
-class AllowPUTAsCreateMixin(object):
-    """
-    The following mixin class may be used in order to support PUT-as-create
-    behavior for incoming requests.
-    """
-    def update(self, request, *args, **kwargs):
-        partial = kwargs.pop('partial', False)
-        instance = self.get_object_or_none()
-        serializer = self.get_serializer(instance, data=request.data, partial=partial)
-        serializer.is_valid(raise_exception=True)
-
-        if instance is None:
-            lookup_url_kwarg = self.lookup_url_kwarg or self.lookup_field
-            lookup_value = self.kwargs[lookup_url_kwarg]
-            extra_kwargs = {self.lookup_field: lookup_value}
-            serializer.save(**extra_kwargs)
-            return Response(serializer.data, status=status.HTTP_201_CREATED)
-
-        serializer.save()
-        return Response(serializer.data)
-
-    def partial_update(self, request, *args, **kwargs):
-        kwargs['partial'] = True
-        return self.update(request, *args, **kwargs)
-
-    def get_object_or_none(self):
-        try:
-            return self.get_object()
-        except Http404:
-            if self.request.method == 'PUT':
-                # For PUT-as-create operation, we need to ensure that we have
-                # relevant permissions, as if this was a POST request.  This
-                # will either raise a PermissionDenied exception, or simply
-                # return None.
-                self.check_permissions(clone_request(self.request, 'POST'))
-            else:
-                # PATCH requests where the object does not exist should still
-                # return a 404 response.
-                raise