Make jingo.Loader properly fall back to other TEMPLATE_LOADERS

- jingo.Loader raises TemplateDoesNotExist when excluded app
  encountered, which causes fallback to the next loader listed in
  settings.TEMPLATE_LOADERS

- renamed setting DJANGO_TEMPLATE_APPS -> JINGO_EXCLUDE_APPS

- tests updated to ensure top-level override of app-level templates
  works for both Jinja and Django loaders

docs/index.rst

@@ -31,7 +31,8 @@ You'll want to use jingo's template loader::
 
     TEMPLATE_LOADERS = (
         'jingo.Loader',
-        'django.template.loaders.filesystem.Loader'
+        'django.template.loaders.filesystem.Loader',
+        'django.template.loaders.app_directories.Loader',
     )
 
 This will let you use ``django.shortcuts.render`` or
@@ -40,11 +41,12 @@ This will let you use ``django.shortcuts.render`` or
 And finally you may have apps that do not use Jinja2, these must be excluded
 from the loader::
 
-    DJANGO_TEMPLATE_APPS = ('debug_toolbar',)
+    JINGO_EXCLUDE_APPS = ('debug_toolbar',)
 
-If a template is in the *app folder*, `debug_toolbar`, Django will handle the
-templating, not Jinja.  If this fails, Django will then move on to the next
-loader.
+If a template is in the *app folder*, `debug_toolbar`, the Jinja loader will
+raise a TemplateDoesNotExist exception. This causes Django to move onto the 
+next loader in TEMPLATE_LOADERS to find a template - in this case,
+``django.template.loaders.filesystem.Loader``
 
 
 Template Helpers

fake_settings.py

@@ -3,9 +3,14 @@ import os
 path = lambda *a: os.path.join(ROOT, *a)
 
 ROOT = os.path.dirname(os.path.abspath(__file__))
+INSTALLED_APPS = (
+    'jingo.tests.jinja_app',
+    'jingo.tests.django_app'
+)
 TEMPLATE_LOADERS = (
     'jingo.Loader',
-    'django.template.loaders.filesystem.Loader'
+    'django.template.loaders.filesystem.Loader',
+    'django.template.loaders.app_directories.Loader',
 )
 TEMPLATE_DIRS = (path('jingo/tests/templates'),)
-DJANGO_TEMPLATE_APPS = ('django_app',)
+JINGO_EXCLUDE_APPS = ('django_app',)

jingo/__init__.py

@@ -5,8 +5,9 @@ import logging
 
 from django import http
 from django.conf import settings
+from django.template.base import TemplateDoesNotExist
 from django.template.context import get_standard_processors
-from django.template.loaders.app_directories import Loader as AppLoader
+from django.template.loader import BaseLoader
 from django.utils.importlib import import_module
 from django.utils.translation import trans_real
 
@@ -165,15 +166,14 @@ class Template(object):
         return self.template.render(context_dict)
 
 
-class Loader(AppLoader):
+class Loader(BaseLoader):
     is_usable = True
 
     def load_template(self, template_name, template_dirs=None):
         if hasattr(template_name, 'rsplit'):
             app = template_name.rsplit('/')[0]
-            if app in getattr(settings, 'DJANGO_TEMPLATE_APPS', []):
-                return super(Loader, self).load_template(
-                        template_name, template_dirs)
+            if app in getattr(settings, 'JINGO_EXCLUDE_APPS', []):
+                raise TemplateDoesNotExist(template_name)
 
         template = env.get_template(template_name)
         return Template(template), template.filename

jingo/tests/django_app/templates/django_app/test_nonoverride.html

@@ -0,0 +1 @@
+{{ 'HELLO WORLD'|truncatewords:"1" }}

jingo/tests/django_app/templates/django_app/test_override.html

@@ -0,0 +1 @@
+{{ 'GOODBYE CRUEL WORLD'|truncatewords:"1" }}

jingo/tests/jinja_app/templates/jinja_app/test_nonoverride.html

@@ -0,0 +1 @@
+{{ 'hello'.upper() }}

jingo/tests/jinja_app/templates/jinja_app/test_override.html

@@ -0,0 +1 @@
+{{ 'goodbye'.upper() }}

jingo/tests/templates/django_app/test_override.html

@@ -0,0 +1 @@
+{{ 'HELLO WORLD'|truncatewords:"1" }}

jingo/tests/templates/jinja_app/test_override.html

@@ -0,0 +1 @@
+{{ 'hello'.upper() }}

jingo/tests/test_loader.py

@@ -11,7 +11,27 @@ def test_render():
     eq_(r.content, 'HELLO')
 
 
+def test_render_no_toplevel_override():
+    r = render(Mock(), 'jinja_app/test_nonoverride.html', {})
+    eq_(r.content, 'HELLO')
+
+
+def test_render_toplevel_override():
+    r = render(Mock(), 'jinja_app/test_override.html', {})
+    eq_(r.content, 'HELLO')
+
+
 def test_render_django():
     r = render(Mock(), 'django_app/test.html', {})
     eq_(r.content, 'HELLO ...\n')
 
+
+def test_render_django_no_toplevel_override():
+    r = render(Mock(), 'django_app/test_nonoverride.html', {})
+    eq_(r.content, 'HELLO ...\n')
+
+
+def test_render_django_toplevel_override():
+    r = render(Mock(), 'django_app/test_override.html', {})
+    eq_(r.content, 'HELLO ...\n')
+