Merge pull request #68 from jpic/prefetch_related_lookups

queryset_sequence/__init__.py

@@ -331,6 +331,20 @@ def _fetch_all(self):
         if self._result_cache is None:
             self._result_cache = list(self._iterable_class(self))
 
+    @property
+    def _prefetch_related_lookups(self):
+        # A hack for ModelChoiceField, which uses internal APIs from QuerySet.
+        # This should be fixed when https://code.djangoproject.com/ticket/29984
+        # is fixed.
+        #
+        # Note that this really just needs to return a truth-y value if any of
+        # the QuerySets are using prefetch_related, but this tries to keep the
+        # type sane at least.
+        result = ()
+        for qs in self._querysets:
+            result += qs._prefetch_related_lookups
+        return result
+
     # Python magic methods.
 
     def __len__(self):

tests/test_querysetsequence.py

@@ -3,6 +3,7 @@
 from unittest.mock import patch
 
 import django
+from django import forms
 from django.core.exceptions import (FieldDoesNotExist,
                                     FieldError,
                                     MultipleObjectsReturned,
@@ -354,6 +355,13 @@ def test_empty_prefetch_related(self):
         """Calling prefetch_related on an empty QuerySetSequence doesn't error."""
         self.empty.prefetch_related('author')
 
+    def test_model_choice_iterator(self):
+        """Ensure that ModelChoiceField works for QuerySetSequence."""
+        f = forms.ModelChoiceField(self.all)
+        self.assertEqual(list(f.choices), [
+            ('', '---------'),
+        ] + [(it.pk, str(it)) for it in self.all])
+
 
 class TestDeferOnly(TestBase):
     def test_defer(self):