Fixed #32980 -- Made models cache related managers.

tests/custom_managers/tests.py

@@ -2,10 +2,10 @@ from django.db import models
 from django.test import TestCase
 
 from .models import (
-    Book, Car, CustomManager, CustomQuerySet, DeconstructibleCustomManager,
-    FastCarAsBase, FastCarAsDefault, FunPerson, OneToOneRestrictedModel,
-    Person, PersonFromAbstract, PersonManager, PublishedBookManager,
-    RelatedModel, RestrictedModel,
+    Book, Car, ConfusedBook, CustomManager, CustomQuerySet,
+    DeconstructibleCustomManager, FastCarAsBase, FastCarAsDefault, FunPerson,
+    OneToOneRestrictedModel, Person, PersonFromAbstract, PersonManager,
+    PublishedBookManager, RelatedModel, RestrictedModel,
 )
 
 
@@ -169,6 +169,10 @@ class CustomManagerTests(TestCase):
             ordered=False,
         )
 
+    def test_fk_related_manager_reused(self):
+        self.assertIs(self.b1.favorite_books, self.b1.favorite_books)
+        self.assertIn('favorite_books', self.b1._state.related_managers_cache)
+
     def test_gfk_related_manager(self):
         Person.objects.create(first_name="Bugs", last_name="Bunny", fun=True, favorite_thing=self.b1)
         Person.objects.create(first_name="Droopy", last_name="Dog", fun=False, favorite_thing=self.b1)
@@ -205,6 +209,60 @@ class CustomManagerTests(TestCase):
             ordered=False,
         )
 
+    def test_gfk_related_manager_reused(self):
+        self.assertIs(
+            self.b1.fun_people_favorite_things,
+            self.b1.fun_people_favorite_things,
+        )
+        self.assertIn(
+            'fun_people_favorite_things',
+            self.b1._state.related_managers_cache,
+        )
+
+    def test_gfk_related_manager_not_reused_when_alternate(self):
+        self.assertIsNot(
+            self.b1.favorite_things(manager='fun_people'),
+            self.b1.favorite_things(manager='fun_people'),
+        )
+
+    def test_gfk_related_manager_no_overlap_when_not_hidden(self):
+        """
+        If a GenericRelation defines a related_query_name (and thus the
+        related_name) which shadows another GenericRelation, it should not
+        cause those separate managers to clash.
+        """
+        book = ConfusedBook.objects.create(
+            title='How to program', author='Rodney Dangerfield',
+        )
+        person = Person.objects.create(
+            first_name='Bugs', last_name='Bunny', fun=True, favorite_thing=book,
+        )
+        fun_person = FunPerson.objects.create(
+            first_name='Droopy', last_name='Dog', fun=False, favorite_thing=book,
+        )
+        # The managers don't collide in the internal cache.
+        self.assertIsNot(book.favorite_things, book.less_favorite_things)
+        self.assertIs(book.favorite_things, book.favorite_things)
+        self.assertIs(book.less_favorite_things, book.less_favorite_things)
+        # Both managers are cached separately despite the collision in names.
+        self.assertIn('favorite_things', book._state.related_managers_cache)
+        self.assertIn('less_favorite_things', book._state.related_managers_cache)
+        # "less_favorite_things" isn't available as a reverse related manager,
+        # so never ends up in the cache.
+        self.assertQuerysetEqual(fun_person.favorite_things.all(), [book])
+        with self.assertRaises(AttributeError):
+            fun_person.less_favorite_things
+        self.assertIn('favorite_things', fun_person._state.related_managers_cache)
+        self.assertNotIn(
+            'less_favorite_things',
+            fun_person._state.related_managers_cache,
+        )
+        # The GenericRelation doesn't exist for Person, only FunPerson, so the
+        # exception prevents the cache from being polluted.
+        with self.assertRaises(AttributeError):
+            person.favorite_things
+        self.assertNotIn('favorite_things', person._state.related_managers_cache)
+
     def test_m2m_related_manager(self):
         bugs = Person.objects.create(first_name="Bugs", last_name="Bunny", fun=True)
         self.b1.authors.add(bugs)
@@ -245,6 +303,16 @@ class CustomManagerTests(TestCase):
             ordered=False,
         )
 
+    def test_m2m_related_forward_manager_reused(self):
+        self.assertIs(self.b1.authors, self.b1.authors)
+        self.assertIn('authors', self.b1._state.related_managers_cache)
+
+    def test_m2m_related_revers_manager_reused(self):
+        bugs = Person.objects.create(first_name='Bugs', last_name='Bunny')
+        self.b1.authors.add(bugs)
+        self.assertIs(bugs.books, bugs.books)
+        self.assertIn('books', bugs._state.related_managers_cache)
+
     def test_removal_through_default_fk_related_manager(self, bulk=True):
         bugs = FunPerson.objects.create(first_name="Bugs", last_name="Bunny", fun=True, favorite_book=self.b1)
         droopy = FunPerson.objects.create(first_name="Droopy", last_name="Dog", fun=False, favorite_book=self.b1)