Fixed #24168 -- Allowed selecting a template engine in a few APIs.

Specifically in rendering shortcuts, template responses, and class-based
views that return template responses.

Also added a test for render_to_response(status=...) which was missing
from fdbfc980.

Thanks Tim and Carl for the review.

4 files changed, 43 insertions, 12 deletions

diff --git a/django/shortcuts.py b/django/shortcuts.py
index 3bb2412526..bbfc99299f 100644
--- a/django/shortcuts.py
+++ b/django/shortcuts.py
@@ -25,7 +25,7 @@ from django.utils.functional import Promise
 def render_to_response(template_name, context=None,
                        context_instance=_context_instance_undefined,
                        content_type=None, status=None, dirs=_dirs_undefined,
-                       dictionary=_dictionary_undefined):
+                       dictionary=_dictionary_undefined, using=None):
     """
     Returns a HttpResponse whose content is filled with the result of calling
     django.template.loader.render_to_string() with the passed arguments.
@@ -34,12 +34,13 @@ def render_to_response(template_name, context=None,
             and dirs is _dirs_undefined
             and dictionary is _dictionary_undefined):
         # No deprecated arguments were passed - use the new code path
-        content = loader.render_to_string(template_name, context)
+        content = loader.render_to_string(template_name, context, using=using)
 
     else:
         # Some deprecated arguments were passed - use the legacy code path
         content = loader.render_to_string(
-            template_name, context, context_instance, dirs, dictionary)
+            template_name, context, context_instance, dirs, dictionary,
+            using=using)
 
     return HttpResponse(content, content_type, status)
 
@@ -47,7 +48,8 @@ def render_to_response(template_name, context=None,
 def render(request, template_name, context=None,
            context_instance=_context_instance_undefined,
            content_type=None, status=None, current_app=_current_app_undefined,
-           dirs=_dirs_undefined, dictionary=_dictionary_undefined):
+           dirs=_dirs_undefined, dictionary=_dictionary_undefined,
+           using=None):
     """
     Returns a HttpResponse whose content is filled with the result of calling
     django.template.loader.render_to_string() with the passed arguments.
@@ -59,7 +61,8 @@ def render(request, template_name, context=None,
             and dictionary is _dictionary_undefined):
         # No deprecated arguments were passed - use the new code path
         # In Django 2.0, request should become a positional argument.
-        content = loader.render_to_string(template_name, context, request=request)
+        content = loader.render_to_string(
+            template_name, context, request=request, using=using)
 
     else:
         # Some deprecated arguments were passed - use the legacy code path
@@ -80,7 +83,8 @@ def render(request, template_name, context=None,
                 context_instance._current_app = current_app
 
         content = loader.render_to_string(
-            template_name, context, context_instance, dirs, dictionary)
+            template_name, context, context_instance, dirs, dictionary,
+            using=using)
 
     return HttpResponse(content, content_type, status)
 
diff --git a/django/template/response.py b/django/template/response.py
index ab9559853a..48295c5e05 100644
--- a/django/template/response.py
+++ b/django/template/response.py
@@ -16,7 +16,7 @@ class SimpleTemplateResponse(HttpResponse):
     rendering_attrs = ['template_name', 'context_data', '_post_render_callbacks']
 
     def __init__(self, template, context=None, content_type=None, status=None,
-                 charset=None):
+                 charset=None, using=None):
         if isinstance(template, Template):
             warnings.warn(
                 "{}'s template argument cannot be a django.template.Template "
@@ -31,6 +31,8 @@ class SimpleTemplateResponse(HttpResponse):
         self.template_name = template
         self.context_data = context
 
+        self.using = using
+
         self._post_render_callbacks = []
 
         # _request stores the current request object in subclasses that know
@@ -73,9 +75,9 @@ class SimpleTemplateResponse(HttpResponse):
     def resolve_template(self, template):
         "Accepts a template object, path-to-template or list of paths"
         if isinstance(template, (list, tuple)):
-            return loader.select_template(template)
+            return loader.select_template(template, using=self.using)
         elif isinstance(template, six.string_types):
-            return loader.get_template(template)
+            return loader.get_template(template, using=self.using)
         else:
             return template
 
@@ -189,7 +191,8 @@ class TemplateResponse(SimpleTemplateResponse):
     rendering_attrs = SimpleTemplateResponse.rendering_attrs + ['_request', '_current_app']
 
     def __init__(self, request, template, context=None, content_type=None,
-            status=None, current_app=_current_app_undefined, charset=None):
+            status=None, current_app=_current_app_undefined, charset=None,
+            using=None):
         # As a convenience we'll allow callers to provide current_app without
         # having to avoid needing to create the RequestContext directly
         if current_app is not _current_app_undefined:
@@ -199,5 +202,5 @@ class TemplateResponse(SimpleTemplateResponse):
                 RemovedInDjango20Warning, stacklevel=2)
             request.current_app = current_app
         super(TemplateResponse, self).__init__(
-            template, context, content_type, status, charset)
+            template, context, content_type, status, charset, using)
         self._request = request
diff --git a/django/test/utils.py b/django/test/utils.py
index 1991602293..f0d8993a40 100644
--- a/django/test/utils.py
+++ b/django/test/utils.py
@@ -3,7 +3,7 @@ import logging
 import re
 import sys
 import time
-from unittest import skipUnless
+from unittest import skipIf, skipUnless
 import warnings
 from functools import wraps
 from xml.dom.minidom import parseString, Node
@@ -20,6 +20,11 @@ from django.utils import six
 from django.utils.encoding import force_str
 from django.utils.translation import deactivate
 
+try:
+    import jinja2
+except ImportError:
+    jinja2 = None
+
 
 __all__ = (
     'Approximate', 'ContextList', 'get_runner',
@@ -573,3 +578,20 @@ def freeze_time(t):
         yield
     finally:
         time.time = _real_time
+
+
+def require_jinja2(test_func):
+    """
+    Decorator to enable a Jinja2 template engine in addition to the regular
+    Django template engine for a test or skip it if Jinja2 isn't available.
+    """
+    test_func = skipIf(jinja2 is None, "this test requires jinja2")(test_func)
+    test_func = override_settings(TEMPLATES=[{
+        'BACKEND': 'django.template.backends.django.DjangoTemplates',
+        'APP_DIRS': True,
+    }, {
+        'BACKEND': 'django.template.backends.jinja2.Jinja2',
+        'APP_DIRS': True,
+        'OPTIONS': {'keep_trailing_newline': True},
+    }])(test_func)
+    return test_func
diff --git a/django/views/generic/base.py b/django/views/generic/base.py
index a873f11f05..88b6608fd2 100644
--- a/django/views/generic/base.py
+++ b/django/views/generic/base.py
@@ -114,6 +114,7 @@ class TemplateResponseMixin(object):
     A mixin that can be used to render a template.
     """
     template_name = None
+    template_engine = None
     response_class = TemplateResponse
     content_type = None
 
@@ -130,6 +131,7 @@ class TemplateResponseMixin(object):
             request=self.request,
             template=self.get_template_names(),
             context=context,
+            using=self.template_engine,
             **response_kwargs
         )