Fixed #17527 -- Improved exception message when adding the wrong type of object to a ManyToManyField. Thanks, guettli and cClaude Paroz.

git-svn-id: http://code.djangoproject.com/svn/django/trunk@17437 bcc190cf-cafb-0310-a4f2-bffc1f526a37

django/db/models/fields/related.py

@@ -474,7 +474,7 @@ class ForeignRelatedObjectsDescriptor(object):
             def add(self, *objs):
                 for obj in objs:
                     if not isinstance(obj, self.model):
-                        raise TypeError("'%s' instance expected" % self.model._meta.object_name)
+                        raise TypeError("'%s' instance expected, got %r" % (self.model._meta.object_name, obj))
                     setattr(obj, rel_field.name, self.instance)
                     obj.save()
             add.alters_data = True
@@ -636,7 +636,7 @@ def create_many_related_manager(superclass, rel):
                                                (obj, self.instance._state.db, obj._state.db))
                         new_ids.add(obj.pk)
                     elif isinstance(obj, Model):
-                        raise TypeError("'%s' instance expected" % self.model._meta.object_name)
+                        raise TypeError("'%s' instance expected, got %r" % (self.model._meta.object_name, obj))
                     else:
                         new_ids.add(obj)
                 db = router.db_for_write(self.through, instance=self.instance)

tests/modeltests/many_to_many/tests.py

@@ -1,4 +1,4 @@
-from __future__ import absolute_import
+from __future__ import absolute_import, with_statement
 
 from django.test import TestCase
 
@@ -52,7 +52,8 @@ class ManyToManyTests(TestCase):
             ])
 
         # Adding an object of the wrong type raises TypeError
-        self.assertRaises(TypeError, a6.publications.add, a5)
+        with self.assertRaisesRegexp(TypeError, "'Publication' instance expected, got <Article.*"):
+            a6.publications.add(a5)
         # Add a Publication directly via publications.add by using keyword arguments.
         p4 = a6.publications.create(title='Highlights for Adults')
         self.assertQuerysetEqual(a6.publications.all(),

tests/modeltests/many_to_one/tests.py

@@ -1,4 +1,4 @@
-from __future__ import absolute_import
+from __future__ import absolute_import, with_statement
 
 from copy import deepcopy
 from datetime import datetime
@@ -68,7 +68,8 @@ class ManyToOneTests(TestCase):
         self.assertQuerysetEqual(self.r2.article_set.all(), ["<Article: Paul's story>"])
 
         # Adding an object of the wrong type raises TypeError.
-        self.assertRaises(TypeError, self.r.article_set.add, self.r2)
+        with self.assertRaisesRegexp(TypeError, "'Article' instance expected, got <Reporter.*"):
+            self.r.article_set.add(self.r2)
         self.assertQuerysetEqual(self.r.article_set.all(),
             [
                 "<Article: John's second story>",