queryset-refactor: Added some sanity checking to __and__() and __or__() because

some people insist on trying to merge a Queryset and a ValuesQuerySet.


git-svn-id: http://code.djangoproject.com/svn/django/branches/queryset-refactor@7342 bcc190cf-cafb-0310-a4f2-bffc1f526a37

1 files changed, 17 insertions, 0 deletions

diff --git a/django/db/models/query.py b/django/db/models/query.py
index f9b8baf3b1..7376d13715 100644
--- a/django/db/models/query.py
+++ b/django/db/models/query.py
@@ -118,12 +118,22 @@ class _QuerySet(object):
         except self.model.DoesNotExist, e:
             raise IndexError, e.args
 
+    def _merge_sanity_check(self, other):
+        """
+        Checks that we are merging two comparable queyrset classes.
+        """
+        if self.__class__ is not other.__class__:
+            raise TypeError("Cannot merge querysets of different types ('%s' and '%s'."
+                    % (self.__class__.__name__, other.__class__.__name__))
+
     def __and__(self, other):
+        self._merge_sanity_check(other)
         combined = self._clone()
         combined.query.combine(other.query, sql.AND)
         return combined
 
     def __or__(self, other):
+        self._merge_sanity_check(other)
         combined = self._clone()
         combined.query.combine(other.query, sql.OR)
         return combined
@@ -527,6 +537,13 @@ class ValuesQuerySet(QuerySet):
             c._setup_query()
         return c
 
+    def _merge_sanity_check(self, other):
+        super(ValuesQuerySet, self)._merge_sanity_check(other)
+        if (set(self.extra_names) != set(other.extra_names) or
+                set(self.field_names) != set(other.field_names)):
+            raise TypeError("Merging '%s' classes must involve the same values in each case."
+                    % self.__class__.__name__)
+
 class ValuesListQuerySet(ValuesQuerySet):
     def iterator(self):
         self.field_names.extend([f for f in self.query.extra_select.keys()])