From e24c0a2d7cab08c2fdcd3f873a3e85f70cd718b4 Mon Sep 17 00:00:00 2001
From: Jon Dufresne <jon.dufresne@gmail.com>
Date: Sun, 11 Sep 2016 08:19:56 -0700
Subject: [PATCH] Fixed #26524 -- Fixed crash in admin change view when
 displaying many to many forward refs.

Thanks Tim Graham for the regression test.
---
 django/contrib/admin/utils.py | 2 +-
 tests/admin_views/models.py   | 4 ++++
 tests/admin_views/tests.py    | 8 ++++++++
 3 files changed, 13 insertions(+), 1 deletion(-)

diff --git a/django/contrib/admin/utils.py b/django/contrib/admin/utils.py
index 9b312ac30e..eb64391647 100644
--- a/django/contrib/admin/utils.py
+++ b/django/contrib/admin/utils.py
@@ -317,7 +317,7 @@ def _get_non_gfk_field(opts, name):
         raise FieldDoesNotExist()
 
     # Avoid coercing <FK>_id fields to FK
-    if field.is_relation and hasattr(field, 'attname') and field.attname == name:
+    if field.is_relation and not field.many_to_many and hasattr(field, 'attname') and field.attname == name:
         raise FieldIsAForeignKeyColumnName()
 
     return field
diff --git a/tests/admin_views/models.py b/tests/admin_views/models.py
index 8828c8b4da..4d500cd9e6 100644
--- a/tests/admin_views/models.py
+++ b/tests/admin_views/models.py
@@ -596,9 +596,13 @@ class CyclicTwo(models.Model):
         return self.name
 
 
+@python_2_unicode_compatible
 class Topping(models.Model):
     name = models.CharField(max_length=20)
 
+    def __str__(self):
+        return self.name
+
 
 class Pizza(models.Model):
     name = models.CharField(max_length=20)
diff --git a/tests/admin_views/tests.py b/tests/admin_views/tests.py
index 3368ddf3d6..ccc38920d0 100644
--- a/tests/admin_views/tests.py
+++ b/tests/admin_views/tests.py
@@ -4696,6 +4696,14 @@ class ReadonlyTest(AdminFieldExtractionMixin, TestCase):
         response = self.client.get(reverse('admin:admin_views_topping_add'))
         self.assertEqual(response.status_code, 200)
 
+    def test_readonly_manytomany_forwards_ref(self):
+        topping = Topping.objects.create(name='Salami')
+        pizza = Pizza.objects.create(name='Americano')
+        pizza.toppings.add(topping)
+        response = self.client.get(reverse('admin:admin_views_pizza_change', args=(pizza.pk,)))
+        self.assertContains(response, '<label>Toppings:</label>', html=True)
+        self.assertContains(response, '<p>Salami</p>', html=True)
+
     def test_readonly_onetoone_backwards_ref(self):
         """
         Can reference a reverse OneToOneField in ModelAdmin.readonly_fields.