Fix #64

It's necessary to force form resolution before rendering. Otherwise
`.qs` will cache an empty form - a result of no filters being requested.

Author: Ryan P Kilby

rest_framework_filters/backends.py

@@ -1,5 +1,8 @@
 
+from django.template import loader
+from rest_framework.compat import template_render
 import rest_framework.filters
+
 from .filterset import FilterSet
 
 
@@ -15,3 +18,18 @@ def filter_queryset(self, request, queryset, view):
             return filter_class(request.query_params, queryset=queryset).qs
 
         return queryset
+
+    def to_html(self, request, queryset, view):
+        filter_class = self.get_filter_class(view, queryset)
+        if not filter_class:
+            return None
+        filter_instance = filter_class(request.query_params, queryset=queryset)
+
+        # forces `form` evaluation before `qs` is called. This prevents an empty form from being cached.
+        filter_instance.form
+
+        context = {
+            'filter': filter_instance
+        }
+        template = loader.get_template(self.template)
+        return template_render(template, context)

tests/settings.py

@@ -1,13 +1,21 @@
+
+DEBUG = True
+
 DATABASES = {
     'default': {
         'ENGINE': 'django.db.backends.sqlite3',
-        'NAME': ':memory:',
+        'NAME': 'db.sqlite3',
+
+        'TEST': {
+            'NAME': ':memory:',
+        },
     },
 }
 
 INSTALLED_APPS = (
     'django.contrib.auth',
     'django.contrib.contenttypes',
+    'django.contrib.staticfiles',
     'rest_framework',
     'tests.testapp',
 )
@@ -26,9 +34,12 @@
                 'django.contrib.auth.context_processors.auth',
                 'django.contrib.messages.context_processors.messages',
             ],
+            'debug': True,
         },
     },
 ]
 
 
 ROOT_URLCONF = 'tests.testapp.urls'
+
+STATIC_URL = '/static/'

tests/testapp/urls.py

@@ -1,6 +1,5 @@
 
 from django.conf.urls import include, url
-from django.contrib import admin
 from rest_framework import routers
 
 from . import views
@@ -13,6 +12,5 @@
 
 
 urlpatterns = [
-    url(r'^admin/', include(admin.site.urls)),
     url(r'^', include(router.urls)),
 ]