Refs #25550 -- Corrected deprecation message for assigning M2M relations.

1 files changed, 15 insertions, 3 deletions

diff --git a/django/db/models/fields/related_descriptors.py b/django/db/models/fields/related_descriptors.py
index de36d4a8e5..4ced1f2c40 100644
--- a/django/db/models/fields/related_descriptors.py
+++ b/django/db/models/fields/related_descriptors.py
@@ -509,6 +509,12 @@ class ReverseManyToOneDescriptor(object):
 
         return self.related_manager_cls(instance)
 
+    def _get_set_deprecation_msg_params(self):
+        return (  # RemovedInDjango20Warning
+            'reverse side of a related set',
+            self.rel.get_accessor_name(),
+        )
+
     def __set__(self, instance, value):
         """
         Set the related objects through the reverse relation.
@@ -520,9 +526,9 @@ class ReverseManyToOneDescriptor(object):
         - ``value`` is the ``children`` sequence on the right of the equal sign
         """
         warnings.warn(
-            'Direct assignment to the reverse side of a related set is '
-            'deprecated due to the implicit save() that happens. Use %s.set() '
-            'instead.' % self.rel.get_accessor_name(), RemovedInDjango20Warning, stacklevel=2,
+            'Direct assignment to the %s is deprecated due to the implicit '
+            'save() that happens. Use %s.set() instead.' % self._get_set_deprecation_msg_params(),
+            RemovedInDjango20Warning, stacklevel=2,
         )
         manager = self.__get__(instance)
         manager.set(value)
@@ -757,6 +763,12 @@ class ManyToManyDescriptor(ReverseManyToOneDescriptor):
             reverse=self.reverse,
         )
 
+    def _get_set_deprecation_msg_params(self):
+        return (  # RemovedInDjango20Warning
+            '%s side of a many-to-many set' % ('reverse' if self.reverse else 'forward'),
+            self.rel.get_accessor_name() if self.reverse else self.field.name,
+        )
+
 
 def create_forward_many_to_many_manager(superclass, rel, reverse):
     """