[1.11.x] Fixed #27998, #28543 -- Restored logging of ManyToManyField changes in admin's object history.

And prevented ManyToManyField initial data in model forms from being affected
by subsequent model changes.

Regression in 56a55566a791a11420fe96f745b7489e756fc931.

Partial backport of e5bd585c6eb1e13e2f8aac030b33c077b0b70c05 and
15b465c584f49a1d43b6c18796f83521ee4ffc22 from master

3 files changed, 34 insertions, 14 deletions

diff --git a/tests/admin_views/admin.py b/tests/admin_views/admin.py
index b5e0ff4814..5d02f0f37d 100644
--- a/tests/admin_views/admin.py
+++ b/tests/admin_views/admin.py
@@ -38,14 +38,14 @@ from .models import (
     OtherStory, Paper, Parent, ParentWithDependentChildren, ParentWithUUIDPK,
     Person, Persona, Picture, Pizza, Plot, PlotDetails, PlotProxy,
     PluggableSearchPerson, Podcast, Post, PrePopulatedPost,
-    PrePopulatedPostLargeSlug, PrePopulatedSubPost, Promo, Question, Recipe,
-    Recommendation, Recommender, ReferencedByGenRel, ReferencedByInline,
-    ReferencedByParent, RelatedPrepopulated, RelatedWithUUIDPKModel, Report,
-    Reservation, Restaurant, RowLevelChangePermissionModel, Section,
-    ShortMessage, Simple, Sketch, State, Story, StumpJoke, Subscriber,
-    SuperVillain, Telegram, Thing, Topping, UnchangeableObject,
-    UndeletableObject, UnorderedObject, UserMessenger, Villain, Vodcast,
-    Whatsit, Widget, Worker, WorkHour,
+    PrePopulatedPostLargeSlug, PrePopulatedSubPost, Promo, Question,
+    ReadablePizza, Recipe, Recommendation, Recommender, ReferencedByGenRel,
+    ReferencedByInline, ReferencedByParent, RelatedPrepopulated,
+    RelatedWithUUIDPKModel, Report, Reservation, Restaurant,
+    RowLevelChangePermissionModel, Section, ShortMessage, Simple, Sketch,
+    State, Story, StumpJoke, Subscriber, SuperVillain, Telegram, Thing,
+    Topping, UnchangeableObject, UndeletableObject, UnorderedObject,
+    UserMessenger, Villain, Vodcast, Whatsit, Widget, Worker, WorkHour,
 )
 
 
@@ -988,6 +988,7 @@ site.register(Book, inlines=[ChapterInline])
 site.register(Promo)
 site.register(ChapterXtra1, ChapterXtra1Admin)
 site.register(Pizza, PizzaAdmin)
+site.register(ReadablePizza)
 site.register(Topping, ToppingAdmin)
 site.register(Album, AlbumAdmin)
 site.register(Question)
diff --git a/tests/admin_views/models.py b/tests/admin_views/models.py
index 9c7eee7547..29d96474c6 100644
--- a/tests/admin_views/models.py
+++ b/tests/admin_views/models.py
@@ -611,6 +611,13 @@ class Pizza(models.Model):
     toppings = models.ManyToManyField('Topping', related_name='pizzas')
 
 
+# Pizza's ModelAdmin has readonly_fields = ['toppings'].
+# toppings is editable for this model's admin.
+class ReadablePizza(Pizza):
+    class Meta:
+        proxy = True
+
+
 class Album(models.Model):
     owner = models.ForeignKey(User, models.SET_NULL, null=True, blank=True)
     title = models.CharField(max_length=30)
diff --git a/tests/admin_views/tests.py b/tests/admin_views/tests.py
index febb20914c..efddc49de7 100644
--- a/tests/admin_views/tests.py
+++ b/tests/admin_views/tests.py
@@ -57,12 +57,13 @@ from .models import (
     MainPrepopulated, Media, ModelWithStringPrimaryKey, OtherStory, Paper,
     Parent, ParentWithDependentChildren, ParentWithUUIDPK, Person, Persona,
     Picture, Pizza, Plot, PlotDetails, PluggableSearchPerson, Podcast, Post,
-    PrePopulatedPost, Promo, Question, Recommendation, Recommender,
-    RelatedPrepopulated, RelatedWithUUIDPKModel, Report, Restaurant,
-    RowLevelChangePermissionModel, SecretHideout, Section, ShortMessage,
-    Simple, State, Story, Subscriber, SuperSecretHideout, SuperVillain,
-    Telegram, TitleTranslation, Topping, UnchangeableObject, UndeletableObject,
-    UnorderedObject, Villain, Vodcast, Whatsit, Widget, Worker, WorkHour,
+    PrePopulatedPost, Promo, Question, ReadablePizza, Recommendation,
+    Recommender, RelatedPrepopulated, RelatedWithUUIDPKModel, Report,
+    Restaurant, RowLevelChangePermissionModel, SecretHideout, Section,
+    ShortMessage, Simple, State, Story, Subscriber, SuperSecretHideout,
+    SuperVillain, Telegram, TitleTranslation, Topping, UnchangeableObject,
+    UndeletableObject, UnorderedObject, Villain, Vodcast, Whatsit, Widget,
+    Worker, WorkHour,
 )
 
 
@@ -879,6 +880,17 @@ class AdminViewBasicTest(AdminViewBasicTestCase):
         response = self.client.get(reverse('admin:admin_views_undeletableobject_change', args=(instance.pk,)))
         self.assertNotContains(response, 'deletelink')
 
+    def test_change_view_logs_m2m_field_changes(self):
+        """Changes to ManyToManyFields are included in the object's history."""
+        pizza = ReadablePizza.objects.create(name='Cheese')
+        cheese = Topping.objects.create(name='cheese')
+        post_data = {'name': pizza.name, 'toppings': [cheese.pk]}
+        response = self.client.post(reverse('admin:admin_views_readablepizza_change', args=(pizza.pk,)), post_data)
+        self.assertRedirects(response, reverse('admin:admin_views_readablepizza_changelist'))
+        pizza_ctype = ContentType.objects.get_for_model(ReadablePizza, for_concrete_model=False)
+        log = LogEntry.objects.filter(content_type=pizza_ctype, object_id=pizza.pk).first()
+        self.assertEqual(log.get_change_message(), 'Changed toppings.')
+
     def test_allows_attributeerror_to_bubble_up(self):
         """
         AttributeErrors are allowed to bubble when raised inside a change list