Fixed #27844 -- Added optimizemigration management command.

django/core/management/commands/optimizemigration.py

@@ -0,0 +1,121 @@
+import sys
+
+from django.apps import apps
+from django.core.management.base import BaseCommand, CommandError
+from django.core.management.utils import run_formatters
+from django.db import migrations
+from django.db.migrations.exceptions import AmbiguityError
+from django.db.migrations.loader import MigrationLoader
+from django.db.migrations.optimizer import MigrationOptimizer
+from django.db.migrations.writer import MigrationWriter
+from django.utils.version import get_docs_version
+
+
+class Command(BaseCommand):
+    help = "Optimizes the operations for the named migration."
+
+    def add_arguments(self, parser):
+        parser.add_argument(
+            "app_label",
+            help="App label of the application to optimize the migration for.",
+        )
+        parser.add_argument(
+            "migration_name", help="Migration name to optimize the operations for."
+        )
+        parser.add_argument(
+            "--check",
+            action="store_true",
+            help="Exit with a non-zero status if the migration can be optimized.",
+        )
+
+    def handle(self, *args, **options):
+        verbosity = options["verbosity"]
+        app_label = options["app_label"]
+        migration_name = options["migration_name"]
+        check = options["check"]
+
+        # Validate app_label.
+        try:
+            apps.get_app_config(app_label)
+        except LookupError as err:
+            raise CommandError(str(err))
+
+        # Load the current graph state.
+        loader = MigrationLoader(None)
+        if app_label not in loader.migrated_apps:
+            raise CommandError(f"App '{app_label}' does not have migrations.")
+        # Find a migration.
+        try:
+            migration = loader.get_migration_by_prefix(app_label, migration_name)
+        except AmbiguityError:
+            raise CommandError(
+                f"More than one migration matches '{migration_name}' in app "
+                f"'{app_label}'. Please be more specific."
+            )
+        except KeyError:
+            raise CommandError(
+                f"Cannot find a migration matching '{migration_name}' from app "
+                f"'{app_label}'."
+            )
+
+        # Optimize the migration.
+        optimizer = MigrationOptimizer()
+        new_operations = optimizer.optimize(migration.operations, migration.app_label)
+        if len(migration.operations) == len(new_operations):
+            if verbosity > 0:
+                self.stdout.write("No optimizations possible.")
+            return
+        else:
+            if verbosity > 0:
+                self.stdout.write(
+                    "Optimizing from %d operations to %d operations."
+                    % (len(migration.operations), len(new_operations))
+                )
+            if check:
+                sys.exit(1)
+
+        # Set the new migration optimizations.
+        migration.operations = new_operations
+
+        # Write out the optimized migration file.
+        writer = MigrationWriter(migration)
+        migration_file_string = writer.as_string()
+        if writer.needs_manual_porting:
+            if migration.replaces:
+                raise CommandError(
+                    "Migration will require manual porting but is already a squashed "
+                    "migration.\nTransition to a normal migration first: "
+                    "https://docs.djangoproject.com/en/%s/topics/migrations/"
+                    "#squashing-migrations" % get_docs_version()
+                )
+            # Make a new migration with those operations.
+            subclass = type(
+                "Migration",
+                (migrations.Migration,),
+                {
+                    "dependencies": migration.dependencies,
+                    "operations": new_operations,
+                    "replaces": [(migration.app_label, migration.name)],
+                },
+            )
+            optimized_migration_name = "%s_optimized" % migration.name
+            optimized_migration = subclass(optimized_migration_name, app_label)
+            writer = MigrationWriter(optimized_migration)
+            migration_file_string = writer.as_string()
+            if verbosity > 0:
+                self.stdout.write(
+                    self.style.MIGRATE_HEADING("Manual porting required") + "\n"
+                    "  Your migrations contained functions that must be manually "
+                    "copied over,\n"
+                    "  as we could not safely copy their implementation.\n"
+                    "  See the comment at the top of the optimized migration for "
+                    "details."
+                )
+        with open(writer.path, "w", encoding="utf-8") as fh:
+            fh.write(migration_file_string)
+        run_formatters([writer.path])
+
+        if verbosity > 0:
+            self.stdout.write(
+                self.style.MIGRATE_HEADING(f"Optimized migration {writer.path}")
+            )

docs/ref/django-admin.txt

@@ -916,6 +916,23 @@ Deletes nonexistent migrations from the ``django_migrations`` table. This is
 useful when migration files replaced by a squashed migration have been removed.
 See :ref:`migration-squashing` for more details.
 
+``optimizemigration``
+---------------------
+
+.. versionadded:: 4.1
+
+.. django-admin:: optimizemigration app_label migration_name
+
+Optimizes the operations for the named migration and overrides the existing
+file. If the migration contains functions that must be manually copied, the
+command creates a new migration file suffixed with ``_optimized`` that is meant
+to replace the named migration.
+
+.. django-admin-option:: --check
+
+Makes ``optimizemigration`` exit with a non-zero status when a migration can be
+optimized.
+
 ``runserver``
 -------------
 
@@ -2056,8 +2073,9 @@ Black formatting
 .. versionadded:: 4.1
 
 The Python files created by :djadmin:`startproject`, :djadmin:`startapp`,
-:djadmin:`makemigrations`, and :djadmin:`squashmigrations` are formatted using
-the ``black`` command if it is present on your ``PATH``.
+:djadmin:`optimizemigration`, :djadmin:`makemigrations`, and
+:djadmin:`squashmigrations` are formatted using the ``black`` command if it is
+present on your ``PATH``.
 
 If you have ``black`` globally installed, but do not wish it used for the
 current project, you can set the ``PATH`` explicitly::

docs/releases/4.1.txt

@@ -239,8 +239,12 @@ Management Commands
   migrations from the ``django_migrations`` table.
 
 * Python files created by :djadmin:`startproject`, :djadmin:`startapp`,
-  :djadmin:`makemigrations`, and :djadmin:`squashmigrations` are now formatted
-  using the ``black`` command if it is present on your ``PATH``.
+  :djadmin:`optimizemigration`, :djadmin:`makemigrations`, and
+  :djadmin:`squashmigrations` are now formatted using the ``black`` command if
+  it is present on your ``PATH``.
+
+* The new :djadmin:`optimizemigration` command allows optimizing operations for
+  a migration.
 
 Migrations
 ~~~~~~~~~~

tests/migrations/test_commands.py

@@ -2810,3 +2810,163 @@ class AppLabelErrorTests(TestCase):
     def test_squashmigrations_app_name_specified_as_label(self):
         with self.assertRaisesMessage(CommandError, self.did_you_mean_auth_error):
             call_command("squashmigrations", "django.contrib.auth", "0002")
+
+    def test_optimizemigration_nonexistent_app_label(self):
+        with self.assertRaisesMessage(CommandError, self.nonexistent_app_error):
+            call_command("optimizemigration", "nonexistent_app", "0002")
+
+    def test_optimizemigration_app_name_specified_as_label(self):
+        with self.assertRaisesMessage(CommandError, self.did_you_mean_auth_error):
+            call_command("optimizemigration", "django.contrib.auth", "0002")
+
+
+class OptimizeMigrationTests(MigrationTestBase):
+    def test_no_optimization_possible(self):
+        out = io.StringIO()
+        with self.temporary_migration_module(
+            module="migrations.test_migrations"
+        ) as migration_dir:
+            call_command(
+                "optimizemigration", "migrations", "0002", stdout=out, no_color=True
+            )
+            migration_file = os.path.join(migration_dir, "0002_second.py")
+            self.assertTrue(os.path.exists(migration_file))
+            call_command(
+                "optimizemigration",
+                "migrations",
+                "0002",
+                stdout=out,
+                no_color=True,
+                verbosity=0,
+            )
+        self.assertEqual(out.getvalue(), "No optimizations possible.\n")
+
+    def test_optimization(self):
+        out = io.StringIO()
+        with self.temporary_migration_module(
+            module="migrations.test_migrations"
+        ) as migration_dir:
+            call_command(
+                "optimizemigration", "migrations", "0001", stdout=out, no_color=True
+            )
+            initial_migration_file = os.path.join(migration_dir, "0001_initial.py")
+            self.assertTrue(os.path.exists(initial_migration_file))
+            with open(initial_migration_file) as fp:
+                content = fp.read()
+                self.assertIn(
+                    '("bool", models.BooleanField'
+                    if HAS_BLACK
+                    else "('bool', models.BooleanField",
+                    content,
+                )
+        self.assertEqual(
+            out.getvalue(),
+            f"Optimizing from 4 operations to 2 operations.\n"
+            f"Optimized migration {initial_migration_file}\n",
+        )
+
+    def test_optimization_no_verbosity(self):
+        out = io.StringIO()
+        with self.temporary_migration_module(
+            module="migrations.test_migrations"
+        ) as migration_dir:
+            call_command(
+                "optimizemigration",
+                "migrations",
+                "0001",
+                stdout=out,
+                no_color=True,
+                verbosity=0,
+            )
+            initial_migration_file = os.path.join(migration_dir, "0001_initial.py")
+            self.assertTrue(os.path.exists(initial_migration_file))
+            with open(initial_migration_file) as fp:
+                content = fp.read()
+                self.assertIn(
+                    '("bool", models.BooleanField'
+                    if HAS_BLACK
+                    else "('bool', models.BooleanField",
+                    content,
+                )
+        self.assertEqual(out.getvalue(), "")
+
+    def test_creates_replace_migration_manual_porting(self):
+        out = io.StringIO()
+        with self.temporary_migration_module(
+            module="migrations.test_migrations_manual_porting"
+        ) as migration_dir:
+            call_command(
+                "optimizemigration", "migrations", "0003", stdout=out, no_color=True
+            )
+            optimized_migration_file = os.path.join(
+                migration_dir, "0003_third_optimized.py"
+            )
+            self.assertTrue(os.path.exists(optimized_migration_file))
+            with open(optimized_migration_file) as fp:
+                content = fp.read()
+                self.assertIn("replaces = [", content)
+        self.assertEqual(
+            out.getvalue(),
+            f"Optimizing from 3 operations to 2 operations.\n"
+            f"Manual porting required\n"
+            f"  Your migrations contained functions that must be manually copied over,"
+            f"\n"
+            f"  as we could not safely copy their implementation.\n"
+            f"  See the comment at the top of the optimized migration for details.\n"
+            f"Optimized migration {optimized_migration_file}\n",
+        )
+
+    def test_fails_squash_migration_manual_porting(self):
+        out = io.StringIO()
+        with self.temporary_migration_module(
+            module="migrations.test_migrations_manual_porting"
+        ) as migration_dir:
+            msg = (
+                "Migration will require manual porting but is already a squashed "
+                "migration.\nTransition to a normal migration first: "
+                "https://docs.djangoproject.com/en/dev/topics/migrations/"
+                "#squashing-migrations"
+            )
+            with self.assertRaisesMessage(CommandError, msg):
+                call_command("optimizemigration", "migrations", "0004", stdout=out)
+            optimized_migration_file = os.path.join(
+                migration_dir, "0004_fourth_optimized.py"
+            )
+            self.assertFalse(os.path.exists(optimized_migration_file))
+        self.assertEqual(
+            out.getvalue(), "Optimizing from 3 operations to 2 operations.\n"
+        )
+
+    @override_settings(MIGRATION_MODULES={"migrations": "migrations.test_migrations"})
+    def test_optimizemigration_check(self):
+        with self.assertRaises(SystemExit):
+            call_command(
+                "optimizemigration", "--check", "migrations", "0001", verbosity=0
+            )
+
+        call_command("optimizemigration", "--check", "migrations", "0002", verbosity=0)
+
+    @override_settings(
+        INSTALLED_APPS=["migrations.migrations_test_apps.unmigrated_app_simple"],
+    )
+    def test_app_without_migrations(self):
+        msg = "App 'unmigrated_app_simple' does not have migrations."
+        with self.assertRaisesMessage(CommandError, msg):
+            call_command("optimizemigration", "unmigrated_app_simple", "0001")
+
+    @override_settings(
+        MIGRATION_MODULES={"migrations": "migrations.test_migrations_clashing_prefix"},
+    )
+    def test_ambigious_prefix(self):
+        msg = (
+            "More than one migration matches 'a' in app 'migrations'. Please "
+            "be more specific."
+        )
+        with self.assertRaisesMessage(CommandError, msg):
+            call_command("optimizemigration", "migrations", "a")
+
+    @override_settings(MIGRATION_MODULES={"migrations": "migrations.test_migrations"})
+    def test_unknown_prefix(self):
+        msg = "Cannot find a migration matching 'nonexistent' from app 'migrations'."
+        with self.assertRaisesMessage(CommandError, msg):
+            call_command("optimizemigration", "migrations", "nonexistent")

tests/migrations/test_migrations_manual_porting/0003_third.py

@@ -0,0 +1,23 @@
+from django.db import migrations
+
+
+def forwards(apps, schema_editor):
+    pass
+
+
+class Migration(migrations.Migration):
+    dependencies = [
+        ("migrations", "0002_second"),
+    ]
+
+    operations = [
+        migrations.AlterUniqueTogether(
+            name="somemodel",
+            unique_together={("id", "name")},
+        ),
+        migrations.AlterUniqueTogether(
+            name="somemodel",
+            unique_together={("name",)},
+        ),
+        migrations.RunPython(forwards, migrations.RunPython.noop),
+    ]

tests/migrations/test_migrations_manual_porting/0004_fourth.py

@@ -0,0 +1,27 @@
+from django.db import migrations
+
+
+def forwards(apps, schema_editor):
+    pass
+
+
+class Migration(migrations.Migration):
+    dependencies = [
+        ("migrations", "0002_second"),
+    ]
+
+    replaces = [
+        ("migrations", "0003_third"),
+    ]
+
+    operations = [
+        migrations.AlterUniqueTogether(
+            name="somemodel",
+            unique_together={("id", "name")},
+        ),
+        migrations.AlterUniqueTogether(
+            name="somemodel",
+            unique_together={("name",)},
+        ),
+        migrations.RunPython(forwards, migrations.RunPython.noop),
+    ]