9999_wagtail_translation.py 文件源码

def __init__(self, name, app_label):
        # by changing app_label here to 'wagtailcore' we trick Django migrations system
        # to think that this migration belongs to wagtailcore app
        # this is necessary to make model name resolution work
        app_label = 'wagtailcore'
        super(Migration, self).__init__(name, app_label)

        # find last wagtailcore migration
        mod_name  = MigrationLoader.migrations_module(app_label)
        if DJANGO_VERSION >= (1, 11):
            # Django 1.11 returns tuple(str, bool) while older versions return str
            mod_name = mod_name[0]
        mod = import_module(mod_name)
        migrations = []
        # this loop acts the same way as MigrationLoader.
        for name in os.listdir(os.path.dirname(mod.__file__)):
            if not name.endswith('.py'):
                continue
            import_name = name.rsplit('.', 1)[0]
            if import_name[0] in '_.~':
                continue
            migrations.append(import_name)
        last_migration = sorted(migrations, reverse=True)[0]
        # By using `replaces` we make sure that this migration doesn't have ambiguous `app_label`.
        # When this migration is applied Django writes only replaced migration
        # to django_migrations table in DB. Otherwise migration would have
        # 'wagtailtranslation' as app_label in django_migrations table and
        # `migrate` command would consider this migration as unapplied due
        # to app_label mismatch.
        self.replaces = [
            (app_label, last_migration),
        ]

        # import operations from wagtail migration we are replacing
        # and prepend them to operations of this migration
        mod_path = '{}.{}'.format(mod_name, last_migration)
        orig_migration = import_module(mod_path).Migration
        self.operations[:0] = orig_migration.operations
        self.dependencies = orig_migration.dependencies

    # Dynamically define AddField operations for all Page field translations.
    # This always uses current AVAILABLE_LANGUAGES setting.
    # In case languages are changed after running this migration, `makemigrations`
    # command would do nothing for Page model. One would have to run `sync_translation_fields`
    # command from modeltranslation to get DB schema in sync.