[1.9.x] Fixed #25466 -- Added backwards compatibility aliases for LoaderOrigin and StringOrigin.

Thanks Simon Charette for the DeprecationInstanceCheck class.

Backport of 8d1a001e from master

django/template/__init__.py

@@ -58,7 +58,8 @@ from .exceptions import TemplateDoesNotExist, TemplateSyntaxError       # NOQA i
 
 # Template parts
 from .base import (                                                     # NOQA isort:skip
-    Context, Node, NodeList, Origin, RequestContext, Template, Variable,
+    Context, Node, NodeList, Origin, RequestContext, StringOrigin, Template,
+    Variable,
 )
 
 # Deprecated in Django 1.8, will be removed in Django 1.10.

django/template/base.py

@@ -60,7 +60,10 @@ from django.template.context import (  # NOQA: imported for backwards compatibil
     BaseContext, Context, ContextPopException, RequestContext,
 )
 from django.utils import six
-from django.utils.deprecation import RemovedInDjango110Warning
+from django.utils.deprecation import (
+    DeprecationInstanceCheck, RemovedInDjango20Warning,
+    RemovedInDjango110Warning,
+)
 from django.utils.encoding import (
     force_str, force_text, python_2_unicode_compatible,
 )
@@ -158,6 +161,11 @@ class Origin(object):
             )
 
 
+class StringOrigin(six.with_metaclass(DeprecationInstanceCheck, Origin)):
+    alternative = 'django.template.Origin'
+    deprecation_warning = RemovedInDjango20Warning
+
+
 class Template(object):
     def __init__(self, template_string, origin=None, name=None, engine=None):
         try:

django/template/loader.py

 import warnings
 
-from django.utils.deprecation import RemovedInDjango110Warning
+from django.utils import six
+from django.utils.deprecation import (
+    DeprecationInstanceCheck, RemovedInDjango20Warning,
+    RemovedInDjango110Warning,
+)
 
 from . import engines
 from .backends.django import DjangoTemplates
+from .base import Origin
 from .engine import (
     _context_instance_undefined, _dictionary_undefined, _dirs_undefined,
 )
@@ -147,3 +152,8 @@ class BaseLoader(base.Loader):
             "django.template.loaders.base.Loader.",
             RemovedInDjango110Warning, stacklevel=2)
         super(BaseLoader, self).__init__(*args, **kwargs)
+
+
+class LoaderOrigin(six.with_metaclass(DeprecationInstanceCheck, Origin)):
+    alternative = 'django.template.Origin'
+    deprecation_warning = RemovedInDjango20Warning

django/utils/deprecation.py

@@ -73,3 +73,12 @@ class RenameMethodsBase(type):
                     setattr(base, old_method_name, wrapper(new_method))
 
         return new_class
+
+
+class DeprecationInstanceCheck(type):
+    def __instancecheck__(self, instance):
+        warnings.warn(
+            "`%s` is deprecated, use `%s` instead." % (self.__name__, self.alternative),
+            self.deprecation_warning, 2
+        )
+        return super(DeprecationInstanceCheck, self).__instancecheck__(instance)

docs/internals/deprecation.txt

@@ -100,6 +100,10 @@ details on these changes.
 * The ``enclosure`` keyword argument to ``SyndicationFeed.add_item()`` will be
   removed.
 
+* The ``django.template.loader.LoaderOrigin`` and
+  ``django.template.base.StringOrigin`` aliases for
+  ``django.template.base.Origin`` will be removed.
+
 .. _deprecation-removed-in-1.10:
 
 1.10

docs/releases/1.9.txt

@@ -818,7 +818,9 @@ debug as ``True``, an instance of ``django.template.loader.LoaderOrigin`` or
 ``django.template.base.StringOrigin`` was set as the origin attribute on the
 template object. These classes have been combined into
 :class:`~django.template.base.Origin` and is now always set regardless of the
-engine debug setting.
+engine debug setting. For a minimal level of backwards compatibility, the old
+class names will be kept as aliases to the new ``Origin`` class until
+Django 2.0.
 
 .. _default-logging-changes-19:
 
@@ -1335,6 +1337,10 @@ Miscellaneous
   deprecated. Use the new ``enclosures`` argument which accepts a list of
   ``Enclosure`` objects instead of a single one.
 
+* The ``django.template.loader.LoaderOrigin`` and
+  ``django.template.base.StringOrigin`` aliases for
+  ``django.template.base.Origin`` are deprecated.
+
 .. _removed-features-1.9:
 
 Features removed in 1.9

tests/deprecation/tests.py

@@ -7,7 +7,9 @@ import warnings
 from django.test import SimpleTestCase
 from django.test.utils import reset_warning_registry
 from django.utils import six
-from django.utils.deprecation import RenameMethodsBase
+from django.utils.deprecation import (
+    DeprecationInstanceCheck, RemovedInNextVersionWarning, RenameMethodsBase,
+)
 from django.utils.encoding import force_text
 
 
@@ -197,3 +199,16 @@ class DeprecatingSimpleTestCaseUrls(unittest.TestCase):
                     "SimpleTestCase.urls is deprecated and will be removed in "
                     "Django 1.10. Use @override_settings(ROOT_URLCONF=...) "
                     "in TempTestCase instead.")
+
+
+class DeprecationInstanceCheckTest(SimpleTestCase):
+    def test_warning(self):
+        class Manager(six.with_metaclass(DeprecationInstanceCheck)):
+            alternative = 'fake.path.Foo'
+            deprecation_warning = RemovedInNextVersionWarning
+
+        msg = '`Manager` is deprecated, use `fake.path.Foo` instead.'
+        with warnings.catch_warnings():
+            warnings.simplefilter('error', category=RemovedInNextVersionWarning)
+            with self.assertRaisesMessage(RemovedInNextVersionWarning, msg):
+                isinstance(object, Manager)