Fixed #30421 -- Allowed symmetrical intermediate table for self-referential ManyToManyField.

tests/m2m_recursive/tests.py

@@ -1,3 +1,5 @@
+import datetime
+
 from django.test import TestCase
 
 from .models import Person
@@ -59,3 +61,59 @@ class RecursiveM2MTests(TestCase):
         self.a.idols.add(self.a)
         self.assertSequenceEqual(self.a.idols.all(), [self.a])
         self.assertSequenceEqual(self.a.stalkers.all(), [self.a])
+
+
+class RecursiveSymmetricalM2MThroughTests(TestCase):
+    @classmethod
+    def setUpTestData(cls):
+        cls.a, cls.b, cls.c, cls.d = [
+            Person.objects.create(name=name)
+            for name in ['Anne', 'Bill', 'Chuck', 'David']
+        ]
+        cls.a.colleagues.add(cls.b, cls.c, through_defaults={
+            'first_meet': datetime.date(2013, 1, 5),
+        })
+        # Add m2m for Anne and Chuck in reverse direction.
+        cls.d.colleagues.add(cls.a, cls.c, through_defaults={
+            'first_meet': datetime.date(2015, 6, 15),
+        })
+
+    def test_recursive_m2m_all(self):
+        for person, colleagues in (
+            (self.a, [self.b, self.c, self.d]),
+            (self.b, [self.a]),
+            (self.c, [self.a, self.d]),
+            (self.d, [self.a, self.c]),
+        ):
+            with self.subTest(person=person):
+                self.assertSequenceEqual(person.colleagues.all(), colleagues)
+
+    def test_recursive_m2m_reverse_add(self):
+        # Add m2m for Anne in reverse direction.
+        self.b.colleagues.add(self.a, through_defaults={
+            'first_meet': datetime.date(2013, 1, 5),
+        })
+        self.assertSequenceEqual(self.a.colleagues.all(), [self.b, self.c, self.d])
+        self.assertSequenceEqual(self.b.colleagues.all(), [self.a])
+
+    def test_recursive_m2m_remove(self):
+        self.b.colleagues.remove(self.a)
+        self.assertSequenceEqual(self.a.colleagues.all(), [self.c, self.d])
+        self.assertSequenceEqual(self.b.colleagues.all(), [])
+
+    def test_recursive_m2m_clear(self):
+        # Clear m2m for Anne.
+        self.a.colleagues.clear()
+        self.assertSequenceEqual(self.a.friends.all(), [])
+        # Reverse m2m relationships is removed.
+        self.assertSequenceEqual(self.c.colleagues.all(), [self.d])
+        self.assertSequenceEqual(self.d.colleagues.all(), [self.c])
+
+    def test_recursive_m2m_set(self):
+        # Set new relationships for Chuck.
+        self.c.colleagues.set([self.b, self.d], through_defaults={
+            'first_meet': datetime.date(2013, 1, 5),
+        })
+        self.assertSequenceEqual(self.c.colleagues.order_by('name'), [self.b, self.d])
+        # Reverse m2m relationships is removed.
+        self.assertSequenceEqual(self.a.colleagues.order_by('name'), [self.b, self.d])