Fixed #18468 testcase to cover SQL Comment

tests/backends/sqlite/test_features.py

@@ -16,3 +16,6 @@ def test_supports_json_field_operational_error(self):
         ):
             with self.assertRaisesMessage(OperationalError, msg):
                 connection.features.supports_json_field
+
+    def test_no_supports_db_comments(self):
+        self.assertFalse(connection.features.supports_db_comments)

tests/migrations/test_commands.py

@@ -3,6 +3,7 @@
 import io
 import os
 import sys
+import unittest
 from unittest import mock
 
 from django.apps import apps
@@ -542,6 +543,45 @@ def test_showmigrations_plan_no_migrations(self):
         call_command('showmigrations', format='plan', stdout=out, verbosity=2, no_color=True)
         self.assertEqual('(no migrations)\n', out.getvalue().lower())
 
+    @unittest.skipIf(connection.vendor == 'sqlite', 'sqlite does not support SQL comment')
+    @override_settings(MIGRATION_MODULES={"migrations": "migrations.test_migrations_db_comment"})
+    def test_migrate_db_comment(self):
+        """
+        Tests basic usage of the migrate command.
+        """
+        # No tables are created
+        self.assertTableNotExists("migrations_author")
+        self.assertTableNotExists("migrations_tribble")
+        self.assertTableNotExists("migrations_book")
+        # Run the migrations to 0001 only
+        stdout = io.StringIO()
+        call_command('migrate', 'migrations', '0001', verbosity=2, stdout=stdout, no_color=True)
+        stdout = stdout.getvalue()
+        self.assertIn('Add field bool_field to tribble', stdout)
+        self.assertIn('Alter field silly_field on author', stdout)
+        # The correct tables exist
+        self.assertTableExists("migrations_author")
+        self.assertTableExists("migrations_tribble")
+        self.assertTableNotExists("migrations_book")
+        # Run migrations all the way
+        call_command("migrate", verbosity=0)
+        # The correct tables exist
+        self.assertTableExists("migrations_author")
+        self.assertTableNotExists("migrations_tribble")
+        self.assertTableExists("migrations_book")
+        # Unmigrate everything
+        stdout = io.StringIO()
+        call_command('migrate', 'migrations', 'zero', verbosity=2, stdout=stdout, no_color=True)
+        stdout = stdout.getvalue()
+        self.assertIn('Unapply all migrations: migrations', stdout)
+        self.assertIn('Unapplying migrations.0002_second... OK', stdout)
+        self.assertIn('Running pre-migrate handlers for application migrations', stdout)
+        self.assertIn('Running post-migrate handlers for application migrations', stdout)
+        # Tables are gone
+        self.assertTableNotExists("migrations_author")
+        self.assertTableNotExists("migrations_tribble")
+        self.assertTableNotExists("migrations_book")
+
     @override_settings(MIGRATION_MODULES={"migrations": "migrations.test_migrations_squashed_complex"})
     def test_showmigrations_plan_squashed(self):
         """

tests/migrations/test_migrations_db_comment/0001_initial.py

@@ -0,0 +1,41 @@
+from django.db import migrations, models
+
+
+class Migration(migrations.Migration):
+    initial = True
+
+    operations = [
+        migrations.CreateModel(
+            "Author",
+            [
+                ("id", models.AutoField(primary_key=True)),
+                ("name", models.CharField(max_length=255, db_comment='db comment to name Field')),
+                ("slug", models.SlugField(null=True)),
+                ("age", models.IntegerField(default=0, db_comment='db comment to age Field')),
+                ("silly_field", models.BooleanField(default=False, db_comment='db comment to bool Field')),
+            ],
+            options={
+                "db_table_comment": "I am table Comment",
+            }
+        ),
+        migrations.CreateModel(
+            "Tribble",
+            [
+                ("id", models.AutoField(primary_key=True)),
+                ("fluffy", models.BooleanField(default=True)),
+            ],
+            options={
+                "db_table_comment": "I am tribble table Comment",
+            }
+        ),
+        migrations.AddField(
+            model_name='tribble',
+            name='bool_field',
+            field=models.BooleanField(default=False, db_comment='new db comment'),
+        ),
+        migrations.AlterField(
+            model_name='author',
+            name='silly_field',
+            field=models.BooleanField(default=True, db_comment='changed db comment')
+        ),
+    ]

tests/migrations/test_migrations_db_comment/0002_second.py

@@ -0,0 +1,29 @@
+from django.db import migrations, models
+
+
+class Migration(migrations.Migration):
+    dependencies = [
+        ("migrations", "0001_initial"),
+    ]
+
+    operations = [
+
+        migrations.DeleteModel("Tribble"),
+
+        migrations.RemoveField("Author", "silly_field"),
+
+        migrations.AddField("Author", "rating",
+                            models.IntegerField(default=0, db_comment='new comment for rating Column')),
+
+        migrations.CreateModel(
+            "Book",
+            [
+                ("id", models.AutoField(primary_key=True)),
+                (
+                    "author",
+                    models.ForeignKey("migrations.Author", models.SET_NULL, db_comment='this is FK', null=True)
+                ),
+            ],
+        )
+
+    ]