Add _result_cache property on FakeQuerySet

This is necessary for model forms with ParentalManyToManyFields to work correctly on Django 1.8-1.9

CHANGELOG.txt

@@ -1,6 +1,10 @@
 Changelog
 =========
 
+3.0.1 (02.02.2017)
+~~~~~~~~~~~~~~~~~~
+* Fix: Added _result_cache property on FakeQuerySet (necessary for model forms with ParentalManyToManyFields to work correctly on Django 1.8-1.9)
+
 3.0 (02.02.2017)
 ~~~~~~~~~~~~~~~~
 * Added support for many-to-many relations (Thejaswi Puthraya, Matt Westcott)

modelcluster/queryset.py

@@ -132,6 +132,18 @@ def order_by(self, *fields):
         sort_by_fields(results, fields)
         return FakeQuerySet(self.model, results)
 
+    # a standard QuerySet will store the results in _result_cache on running the query;
+    # this is effectively the same as self.results on a FakeQuerySet, and so we'll make
+    # _result_cache an alias of self.results for the benefit of Django internals that
+    # exploit it
+    def _get_result_cache(self):
+        return self.results
+
+    def _set_result_cache(self, val):
+        self.results = list(val)
+
+    _result_cache = property(_get_result_cache, _set_result_cache)
+
     def __getitem__(self, k):
         return self.results[k]
 

setup.py

@@ -7,7 +7,7 @@
 
 setup(
     name='django-modelcluster',
-    version='3.0',
+    version='3.0.1a1',
     description="Django extension to allow working with 'clusters' of models as a single unit, independently of the database",
     author='Matthew Westcott',
     author_email='matthew.westcott@torchbox.com',

tests/tests/test_cluster_form.py

@@ -3,9 +3,9 @@
 from django.utils.six import text_type
 
 from django.test import TestCase
-from tests.models import Band, BandMember, Album, Restaurant
+from tests.models import Band, BandMember, Album, Restaurant, Article, Author, Category
 from modelcluster.forms import ClusterForm
-from django.forms import Textarea, CharField
+from django.forms import Textarea, CharField, ModelForm
 from django.forms.widgets import TextInput
 
 import datetime
@@ -497,3 +497,28 @@ class Meta:
 
         self.assertIn(text_type(form.media['js']), 'test.js')
         self.assertIn(text_type(form.media['css']), 'test.css')
+
+
+class FormWithM2MTest(TestCase):
+    def test_render_form_with_m2m(self):
+        class ArticleForm(ModelForm):
+            class Meta:
+                model = Article
+                fields = ['title', 'authors', 'categories']
+
+        author1 = Author.objects.create(name='James Joyce')
+        author2 = Author.objects.create(name='Charles Dickens')
+        article = Article.objects.create(
+            title='Test article',
+            authors=[author1]
+        )
+
+        form = ArticleForm(instance=article)
+        html = form.as_p()
+        self.assertIn('Test article', html)
+
+        article.authors.add(author2)
+
+        form = ArticleForm(instance=article)
+        html = form.as_p()
+        self.assertIn('Test article', html)