Merge pull request #88 from jrief/fix-mix-polymorphic-with-parler

django-polymorphic does not work with django-parler

.travis.yml

@@ -16,14 +16,18 @@ matrix:
     env: DJANGO=django==1.4.5
   - python: "3.2"
     env: DJANGO=django==1.4.5
+
 install:
-  - "pip install $DJANGO coverage==3.6 --use-mirrors"
+  - pip install $DJANGO coverage==3.6
+
 script:
   - coverage run --source=polymorphic runtests.py
   - coverage report -m
+
 after_success:
-  - "pip install coveralls==0.2 --use-mirrors"
+  - pip install coveralls==0.2
   - coveralls
+
 branches:
   only:
     - master

polymorphic/admin.py

@@ -15,8 +15,16 @@ from django.shortcuts import render_to_response
 from django.template.context import RequestContext
 from django.utils import six
 from django.utils.encoding import force_text
+from django.utils.http import urlencode
 from django.utils.safestring import mark_safe
 from django.utils.translation import ugettext_lazy as _
+try:
+    # Django 1.6 implements this
+    from django.contrib.admin.templatetags.admin_urls import add_preserved_filters
+except ImportError:
+    def add_preserved_filters(context, form_url):
+        return form_url
+
 
 __all__ = (
     'PolymorphicModelChoiceForm', 'PolymorphicParentModelAdmin',
@@ -227,6 +235,12 @@ class PolymorphicParentModelAdmin(admin.ModelAdmin):
             return self.add_type_view(request)
         else:
             real_admin = self._get_real_admin_by_ct(ct_id)
+            # rebuild form_url, otherwise libraries below will override it.
+            form_url = add_preserved_filters({
+                'preserved_filters': urlencode({'ct_id': ct_id}),
+                'opts': self.model._meta},
+                form_url
+            )
             return real_admin.add_view(request, form_url, extra_context)