Fixed #23953 -- Made makemigrations continue number sequence for squashed migrations.

django/db/migrations/autodetector.py

@@ -1329,8 +1329,11 @@ class MigrationAutodetector:
     def parse_number(cls, name):
         """
         Given a migration name, try to extract a number from the beginning of
-        it. If no number is found, return None.
+        it. For a squashed migration such as '0001_squashed_0004…', return the
+        second number. If no number is found, return None.
         """
+        if squashed_match := re.search(r'.*_squashed_(\d+)', name):
+            return int(squashed_match[1])
         match = re.match(r'^\d+', name)
         if match:
             return int(match[0])

tests/migrations/test_autodetector.py

@@ -2670,6 +2670,12 @@ class AutodetectorTests(TestCase):
             ('0001_initial', 1),
             ('0002_model3', 2),
             ('0002_auto_20380101_1112', 2),
+            ('0002_squashed_0003', 3),
+            ('0002_model2_squashed_0003_other4', 3),
+            ('0002_squashed_0003_squashed_0004', 4),
+            ('0002_model2_squashed_0003_other4_squashed_0005_other6', 5),
+            ('0002_custom_name_20380101_1112_squashed_0003_model', 3),
+            ('2_squashed_4', 4),
         ]
         for migration_name, expected_number in tests:
             with self.subTest(migration_name=migration_name):

tests/migrations/test_commands.py

@@ -1956,6 +1956,21 @@ class MakeMigrationsTests(MigrationTestBase):
             out_value = out.getvalue()
             self.assertIn('Add field created to book', out_value)
 
+    @override_settings(
+        MIGRATION_MODULES={'migrations': 'migrations.test_migrations_squashed'},
+    )
+    def test_makemigrations_continues_number_sequence_after_squash(self):
+        with self.temporary_migration_module(module='migrations.test_migrations_squashed'):
+            with captured_stdout() as out:
+                call_command(
+                    'makemigrations',
+                    'migrations',
+                    interactive=False,
+                    empty=True,
+                )
+            out_value = out.getvalue()
+            self.assertIn('0003_auto', out_value)
+
 
 class SquashMigrationsTests(MigrationTestBase):
     """