Fixed #24375 -- Added Migration.initial attribute

The new attribute is checked when the `migrate --fake-initial` option
is used. initial will be set to True for all initial migrations (this
is particularly useful when initial migrations are split) as well as
for squashed migrations.

AUTHORS

@@ -40,6 +40,7 @@ answer newbie questions, and generally made Django that much better:
     Ana Krivokapic <https://github.com/infraredgirl>
     Andi Albrecht <albrecht.andi@gmail.com>
     André Ericson <de.ericson@gmail.com>
+    Andrei Kulakov <andrei.avk@gmail.com>
     Andreas
     Andreas Mock <andreas.mock@web.de>
     Andreas Pelme <andreas@pelme.se>

django/core/management/commands/squashmigrations.py

@@ -131,6 +131,7 @@ class Command(BaseCommand):
             "dependencies": dependencies,
             "operations": new_operations,
             "replaces": replaces,
+            "initial": True,
         })
         new_migration = subclass("0001_squashed_%s" % migration.name, app_label)
 

django/db/migrations/autodetector.py

@@ -33,6 +33,7 @@ class MigrationAutodetector(object):
         self.from_state = from_state
         self.to_state = to_state
         self.questioner = questioner or MigrationQuestioner()
+        self.existing_apps = {app for app, model in from_state.models}
 
     def changes(self, graph, trim_to_apps=None, convert_apps=None, migration_name=None):
         """
@@ -297,6 +298,7 @@ class MigrationAutodetector(object):
                         instance = subclass("auto_%i" % (len(self.migrations.get(app_label, [])) + 1), app_label)
                         instance.dependencies = list(dependencies)
                         instance.operations = chopped
+                        instance.initial = app_label not in self.existing_apps
                         self.migrations.setdefault(app_label, []).append(instance)
                         chop_mode = False
                     else:

django/db/migrations/executor.py

@@ -197,19 +197,25 @@ class MigrationExecutor(object):
     def detect_soft_applied(self, project_state, migration):
         """
         Tests whether a migration has been implicitly applied - that the
-        tables it would create exist. This is intended only for use
-        on initial migrations (as it only looks for CreateModel).
+        tables or columns it would create exist. This is intended only for use
+        on initial migrations (as it only looks for CreateModel and AddField).
         """
-        # Bail if the migration isn't the first one in its app
-        if [name for app, name in migration.dependencies if app == migration.app_label]:
+        if migration.initial is None:
+            # Bail if the migration isn't the first one in its app
+            if any(app == migration.app_label for app, name in migration.dependencies):
+                return False, project_state
+        elif migration.initial is False:
+            # Bail if it's NOT an initial migration
             return False, project_state
+
         if project_state is None:
             after_state = self.loader.project_state((migration.app_label, migration.name), at_end=True)
         else:
             after_state = migration.mutate_state(project_state)
         apps = after_state.apps
-        found_create_migration = False
-        # Make sure all create model are done
+        found_create_model_migration = False
+        found_add_field_migration = False
+        # Make sure all create model and add field operations are done
         for operation in migration.operations:
             if isinstance(operation, migrations.CreateModel):
                 model = apps.get_model(migration.app_label, operation.name)
@@ -217,9 +223,26 @@ class MigrationExecutor(object):
                     # We have to fetch the model to test with from the
                     # main app cache, as it's not a direct dependency.
                     model = global_apps.get_model(model._meta.swapped)
+                if model._meta.proxy or not model._meta.managed:
+                    continue
                 if model._meta.db_table not in self.connection.introspection.table_names(self.connection.cursor()):
                     return False, project_state
-                found_create_migration = True
-        # If we get this far and we found at least one CreateModel migration,
+                found_create_model_migration = True
+            elif isinstance(operation, migrations.AddField):
+                model = apps.get_model(migration.app_label, operation.model_name)
+                if model._meta.swapped:
+                    # We have to fetch the model to test with from the
+                    # main app cache, as it's not a direct dependency.
+                    model = global_apps.get_model(model._meta.swapped)
+                if model._meta.proxy or not model._meta.managed:
+                    continue
+
+                table = model._meta.db_table
+                db_field = model._meta.get_field(operation.name).column
+                fields = self.connection.introspection.get_table_description(self.connection.cursor(), table)
+                if db_field not in (f.name for f in fields):
+                    return False, project_state
+                found_add_field_migration = True
+        # If we get this far and we found at least one CreateModel or AddField migration,
         # the migration is considered implicitly applied.
-        return found_create_migration, after_state
+        return (found_create_model_migration or found_add_field_migration), after_state

django/db/migrations/migration.py

@@ -41,6 +41,13 @@ class Migration(object):
     # are not applied.
     replaces = []
 
+    # Is this an initial migration? Initial migrations are skipped on
+    # --fake-initial if the table or fields already exist. If None, check if
+    # the migration has any dependencies to determine if there are dependencies
+    # to tell if db introspection needs to be done. If True, always perform
+    # introspection. If False, never perform introspection.
+    initial = None
+
     def __init__(self, name, app_label):
         self.name = name
         self.app_label = app_label

django/db/migrations/writer.py

@@ -155,6 +155,7 @@ class MigrationWriter(object):
         """
         items = {
             "replaces_str": "",
+            "initial_str": "",
         }
 
         imports = set()
@@ -211,6 +212,9 @@ class MigrationWriter(object):
         if self.migration.replaces:
             items['replaces_str'] = "\n    replaces = %s\n" % self.serialize(self.migration.replaces)[0]
 
+        if self.migration.initial:
+            items['initial_str'] = "\n    initial = True\n"
+
         return (MIGRATION_TEMPLATE % items).encode("utf8")
 
     @staticmethod
@@ -508,7 +512,7 @@ from __future__ import unicode_literals
 %(imports)s
 
 class Migration(migrations.Migration):
-%(replaces_str)s
+%(replaces_str)s%(initial_str)s
     dependencies = [
 %(dependencies)s\
     ]

docs/releases/1.9.txt

@@ -368,6 +368,14 @@ Management Commands
   to the database using the password from your settings file (instead of
   requiring it to be manually entered).
 
+Migrations
+^^^^^^^^^^
+
+* Initial migrations are now marked with an :attr:`initial = True
+  <django.db.migrations.Migration.initial>` class attribute which allows
+  :djadminopt:`migrate --fake-initial <--fake-initial>` to more easily detect
+  initial migrations.
+
 Models
 ^^^^^^
 

docs/topics/migrations.txt

@@ -276,6 +276,33 @@ class to make it importable::
 Please refer to the notes about :ref:`historical-models` in migrations to see
 the implications that come along.
 
+Initial migrations
+~~~~~~~~~~~~~~~~~~
+
+.. attribute:: Migration.initial
+
+.. versionadded:: 1.9
+
+The "initial migrations" for an app are the migrations that create the first
+version of that app's tables. Usually an app will have just one initial
+migration, but in some cases of complex model interdependencies it may have two
+or more.
+
+Initial migrations are marked with an ``initial = True`` class attribute on the
+migration class. If an ``initial`` class attribute isn't found, a migration
+will be considered "initial" if it is the first migration in the app (i.e. if
+it has no dependencies on any other migration in the same app).
+
+When :djadmin:`migrate` is run with the :djadminopt:`--fake-initial` option,
+these initial migrations are treated specially. For an initial migration that
+creates one or more tables (``CreateModel`` operation), Django checks that all
+of those tables already exist in the database and fake-applies the migration
+if so. Similarly, for an initial migration that adds one or more fields
+(``AddField`` operation), Django checks that all of the respective columns
+already exist in the database and fake-applies the migration if so. Without
+:djadminopt:`--fake-initial`, initial migrations are treated no differently
+from any other migration.
+
 Adding migrations to apps
 -------------------------
 
@@ -425,6 +452,7 @@ Then, open up the file; it should look something like this::
     from django.db import models, migrations
 
     class Migration(migrations.Migration):
+        initial = True
 
         dependencies = [
             ('yourappname', '0001_initial'),
@@ -460,6 +488,7 @@ need to do is use the historical model and iterate over the rows::
             person.save()
 
     class Migration(migrations.Migration):
+        initial = True
 
         dependencies = [
             ('yourappname', '0001_initial'),
@@ -761,12 +790,6 @@ If you already have pre-existing migrations created with
   without running them. (Django won't check that the table schema match your
   models, just that the right table names exist).
 
-That's it! The only complication is if you have a circular dependency loop
-of foreign keys; in this case, ``makemigrations`` might make more than one
-initial migration, and you'll need to mark them all as applied using::
-
-    python manage.py migrate --fake yourappnamehere
-
 .. versionchanged:: 1.8
 
     The :djadminopt:`--fake-initial` flag was added to :djadmin:`migrate`;

tests/migrations/test_autodetector.py

@@ -877,6 +877,9 @@ class AutodetectorTests(TestCase):
         self.assertOperationTypes(changes, 'otherapp', 1, ["AddField"])
         self.assertMigrationDependencies(changes, 'otherapp', 0, [])
         self.assertMigrationDependencies(changes, 'otherapp', 1, [("otherapp", "auto_1"), ("testapp", "auto_1")])
+        # both split migrations should be `initial`
+        self.assertTrue(changes['otherapp'][0].initial)
+        self.assertTrue(changes['otherapp'][1].initial)
 
     def test_same_app_circular_fk_dependency(self):
         """

tests/migrations/test_commands.py

@@ -50,6 +50,30 @@ class MigrateTests(MigrationTestBase):
         self.assertTableNotExists("migrations_tribble")
         self.assertTableNotExists("migrations_book")
 
+    @override_settings(MIGRATION_MODULES={"migrations": "migrations.test_migrations_initial_false"})
+    def test_migrate_initial_false(self):
+        """
+        `Migration.initial = False` skips fake-initial detection.
+        """
+        # Make sure no tables are created
+        self.assertTableNotExists("migrations_author")
+        self.assertTableNotExists("migrations_tribble")
+        # Run the migrations to 0001 only
+        call_command("migrate", "migrations", "0001", verbosity=0)
+        # Fake rollback
+        call_command("migrate", "migrations", "zero", fake=True, verbosity=0)
+        # Make sure fake-initial detection does not run
+        with self.assertRaises(DatabaseError):
+            call_command("migrate", "migrations", "0001", fake_initial=True, verbosity=0)
+
+        call_command("migrate", "migrations", "0001", fake=True, verbosity=0)
+        # Real rollback
+        call_command("migrate", "migrations", "zero", verbosity=0)
+        # Make sure it's all gone
+        self.assertTableNotExists("migrations_author")
+        self.assertTableNotExists("migrations_tribble")
+        self.assertTableNotExists("migrations_book")
+
     @override_settings(MIGRATION_MODULES={"migrations": "migrations.test_migrations"})
     def test_migrate_fake_initial(self):
         """
@@ -109,6 +133,24 @@ class MigrateTests(MigrationTestBase):
         self.assertTableNotExists("migrations_tribble")
         self.assertTableNotExists("migrations_book")
 
+    @override_settings(MIGRATION_MODULES={"migrations": "migrations.test_migrations_fake_split_initial"})
+    def test_migrate_fake_split_initial(self):
+        """
+        Split initial migrations can be faked with --fake-initial.
+        """
+        call_command("migrate", "migrations", "0002", verbosity=0)
+        call_command("migrate", "migrations", "zero", fake=True, verbosity=0)
+        out = six.StringIO()
+        with mock.patch('django.core.management.color.supports_color', lambda *args: False):
+            call_command("migrate", "migrations", "0002", fake_initial=True, stdout=out, verbosity=1)
+        value = out.getvalue().lower()
+        self.assertIn("migrations.0001_initial... faked", value)
+        self.assertIn("migrations.0002_second... faked", value)
+        # Fake an apply
+        call_command("migrate", "migrations", fake=True, verbosity=0)
+        # Unmigrate everything
+        call_command("migrate", "migrations", "zero", verbosity=0)
+
     @override_settings(MIGRATION_MODULES={"migrations": "migrations.test_migrations_conflict"})
     def test_migrate_conflict_exit(self):
         """
@@ -409,6 +451,7 @@ class MakeMigrationsTests(MigrationTestBase):
                 content = fp.read()
                 self.assertIn('# -*- coding: utf-8 -*-', content)
                 self.assertIn('migrations.CreateModel', content)
+                self.assertIn('initial = True', content)
 
                 if six.PY3:
                     self.assertIn('úñí©óðé µóðéø', content)  # Meta.verbose_name
@@ -882,6 +925,15 @@ class SquashMigrationsTests(MigrationTestBase):
             squashed_migration_file = os.path.join(migration_dir, "0001_squashed_0002_second.py")
             self.assertTrue(os.path.exists(squashed_migration_file))
 
+    def test_squashmigrations_initial_attribute(self):
+        with self.temporary_migration_module(module="migrations.test_migrations") as migration_dir:
+            call_command("squashmigrations", "migrations", "0002", interactive=False, verbosity=0)
+
+            squashed_migration_file = os.path.join(migration_dir, "0001_squashed_0002_second.py")
+            with codecs.open(squashed_migration_file, "r", encoding="utf-8") as fp:
+                content = fp.read()
+                self.assertIn("initial = True", content)
+
     def test_squashmigrations_optimizes(self):
         """
         Tests that squashmigrations optimizes operations.

tests/migrations/test_migrations/0001_initial.py

@@ -6,6 +6,8 @@ from django.db import migrations, models
 
 class Migration(migrations.Migration):
 
+    initial = True
+
     operations = [
 
         migrations.CreateModel(

tests/migrations/test_migrations_fake_split_initial/0001_initial.py

@@ -0,0 +1,33 @@
+# -*- coding: utf-8 -*-
+from __future__ import unicode_literals
+
+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)),
+                ("slug", models.SlugField(null=True)),
+                ("age", models.IntegerField(default=0)),
+                ("silly_field", models.BooleanField(default=False)),
+            ],
+        ),
+        migrations.CreateModel(
+            "Tribble",
+            [
+                ("id", models.AutoField(primary_key=True)),
+                ("fluffy", models.BooleanField(default=True)),
+            ],
+        ),
+        migrations.AlterUniqueTogether(
+            name='author',
+            unique_together=set([('name', 'slug')]),
+        ),
+    ]

tests/migrations/test_migrations_fake_split_initial/0002_second.py

@@ -0,0 +1,24 @@
+# -*- coding: utf-8 -*-
+from __future__ import unicode_literals
+
+from django.db import migrations, models
+
+
+class Migration(migrations.Migration):
+
+    initial = True
+
+    dependencies = [
+        ("migrations", "0001_initial"),
+    ]
+
+    operations = [
+        migrations.AddField("Author", "rating", models.IntegerField(default=0)),
+        migrations.CreateModel(
+            "Book",
+            [
+                ("id", models.AutoField(primary_key=True)),
+                ("author", models.ForeignKey("migrations.Author", null=True)),
+            ],
+        ),
+    ]

tests/migrations/test_migrations_initial_false/0001_not_initial.py

@@ -0,0 +1,33 @@
+# -*- coding: utf-8 -*-
+from __future__ import unicode_literals
+
+from django.db import migrations, models
+
+
+class Migration(migrations.Migration):
+
+    initial = False
+
+    operations = [
+        migrations.CreateModel(
+            "Author",
+            [
+                ("id", models.AutoField(primary_key=True)),
+                ("name", models.CharField(max_length=255)),
+                ("slug", models.SlugField(null=True)),
+                ("age", models.IntegerField(default=0)),
+                ("silly_field", models.BooleanField(default=False)),
+            ],
+        ),
+        migrations.CreateModel(
+            "Tribble",
+            [
+                ("id", models.AutoField(primary_key=True)),
+                ("fluffy", models.BooleanField(default=True)),
+            ],
+        ),
+        migrations.AlterUniqueTogether(
+            name='author',
+            unique_together=set([('name', 'slug')]),
+        ),
+    ]