Fixed #36791 -- Made MigrationAutodetector recreate through table when m2m target model changes.

Co-Authored-By: Jacob Walls <38668450+jacobtylerwalls@users.noreply.github.com>
Co-Authored-By: Clifford Gama <cliffygamy@gmail.com>

2 files changed, 51 insertions, 1 deletions

diff --git a/django/db/migrations/autodetector.py b/django/db/migrations/autodetector.py
index 7cc22c0637..0c2e215fcd 100644
--- a/django/db/migrations/autodetector.py
+++ b/django/db/migrations/autodetector.py
@@ -1339,7 +1339,10 @@ class MigrationAutodetector:
             if old_field_dec != new_field_dec and old_field_name == field_name:
                 both_m2m = old_field.many_to_many and new_field.many_to_many
                 neither_m2m = not old_field.many_to_many and not new_field.many_to_many
-                if both_m2m or neither_m2m:
+                target_changed = (
+                    both_m2m and new_field_dec[2]["to"] != old_field_dec[2]["to"]
+                )
+                if (both_m2m or neither_m2m) and not target_changed:
                     # Either both fields are m2m or neither is
                     preserve_default = True
                     if (
diff --git a/tests/migrations/test_autodetector.py b/tests/migrations/test_autodetector.py
index c044cc9a99..e333621855 100644
--- a/tests/migrations/test_autodetector.py
+++ b/tests/migrations/test_autodetector.py
@@ -741,6 +741,13 @@ class AutodetectorTests(BaseAutodetectorTests):
             ("publishers", models.ManyToManyField("testapp.Publisher", blank=True)),
         ],
     )
+    other_publisher = ModelState(
+        "testapp",
+        "OtherPublisher",
+        [
+            ("id", models.AutoField(primary_key=True)),
+        ],
+    )
     author_with_m2m_through = ModelState(
         "testapp",
         "Author",
@@ -4557,6 +4564,46 @@ class AutodetectorTests(BaseAutodetectorTests):
         )
         self.assertOperationFieldAttributes(changes, "testapp", 0, 2, max_length=100)
 
+    def test_m2m_target_change_generates_remove_and_add(self):
+        before = [
+            self.publisher,
+            self.other_publisher,
+            self.author_with_m2m,  # m2m to self.publisher.
+        ]
+
+        after = [
+            self.publisher,
+            self.other_publisher,
+            ModelState(
+                "testapp",
+                "Author",
+                [
+                    ("id", models.AutoField(primary_key=True)),
+                    # Repoint m2m to self.other_publisher.
+                    ("publishers", models.ManyToManyField("testapp.OtherPublisher")),
+                ],
+            ),
+        ]
+        changes = self.get_changes(before, after)
+        self.assertNumberMigrations(changes, "testapp", 1)
+        self.assertOperationTypes(changes, "testapp", 0, ["RemoveField", "AddField"])
+        self.assertOperationAttributes(
+            changes,
+            "testapp",
+            0,
+            0,
+            name="publishers",
+            model_name="author",
+        )
+        self.assertOperationAttributes(
+            changes,
+            "testapp",
+            0,
+            1,
+            name="publishers",
+            model_name="author",
+        )
+
     def test_non_circular_foreignkey_dependency_removal(self):
         """
         If two models with a ForeignKey from one to the other are removed at