questioner.py 文件源码

def ask_not_null_alteration(self, field_name, model_name):
        "Changing a NULL field to NOT NULL"
        if not self.dry_run:
            choice = self._choice_input(
                "You are trying to change the nullable field '%s' on %s to non-nullable "
                "without a default; we can't do that (the database needs something to "
                "populate existing rows).\n"
                "Please select a fix:" % (field_name, model_name),
                [
                    "Provide a one-off default now (will be set on all existing rows)",
                    ("Ignore for now, and let me handle existing rows with NULL myself "
                     "(e.g. because you added a RunPython or RunSQL operation to handle "
                     "NULL values in a previous data migration)"),
                    "Quit, and let me add a default in models.py",
                ]
            )
            if choice == 2:
                return NOT_PROVIDED
            elif choice == 3:
                sys.exit(3)
            else:
                return self._ask_default()
        return None