Better naming, and prompt for NOT NULL field addition

import re

import sys

from django.utils import datetime_safe

from django.utils.six.moves import input

from django.db.migrations import operations

from django.db.migrations.migration import Migration

            old_field_names = set([x for x, y in old_model_state.fields])

            new_field_names = set([x for x, y in new_model_state.fields])

            for field_name in new_field_names - old_field_names:

                field = [y for x, y in new_model_state.fields if x == field_name][0]

                # You can't just add NOT NULL fields with no default

                if not field.null and not field.has_default():

                    field.default = self.questioner.ask_not_null_addition(field_name, model_name)

                self.add_to_migration(

                    app_label,

                    operations.AddField(

                        model_name = model_name,

                        name = field_name,

                        field = [y for x, y in new_model_state.fields if x == field_name][0],

                        field = field,

                    )

                )

            # Old fields

                return ops[0].name.lower()

            elif isinstance(ops[0], operations.DeleteModel):

                return "delete_%s" % ops[0].name.lower()

            elif isinstance(ops[0], operations.AddField):

                return "%s_%s" % (ops[0].model_name.lower(), ops[0].name.lower())

            elif isinstance(ops[0], operations.RemoveField):

                return "remove_%s_%s" % (ops[0].model_name.lower(), ops[0].name.lower())

        elif all(isinstance(o, operations.CreateModel) for o in ops):

            return "_".join(sorted(o.name.lower() for o in ops))

        return "auto"

        "Should we create an initial migration for the app?"

        return self.defaults.get("ask_initial", False)

    def ask_not_null_addition(self, field_name, model_name):

        "Adding a NOT NULL field to a model"

        # None means quit

        return None

class InteractiveMigrationQuestioner(MigrationQuestioner):

            result = input("Please answer yes or no: ")

        return result[0].lower() == "y"

    def _choice_input(self, question, choices):

        print question

        for i, choice in enumerate(choices):

            print " %s) %s" % (i + 1, choice)

        result = input("Select an option: ")

        while True:

            try:

                value = int(result)

                if 0 < value <= len(choices):

                    return value

            except ValueError:

                pass

            result = input("Please select a valid option: ")

    def ask_initial(self, app_label):

        "Should we create an initial migration for the app?"

        # Don't ask for django.contrib apps

        app = cache.get_app(app_label)

        if app.__name__.startswith("django.contrib"):

            return True

        # Now ask

        return self._boolean_input("Do you want to enable migrations for app '%s'?" % app_label)

    def ask_not_null_addition(self, field_name, model_name):

        "Adding a NOT NULL field to a model"

        choice = self._choice_input(

            "You are trying to add a non-nullable field '%s' to %s without a default;\n" % (field_name, model_name) +

            "this is not possible. Please select a fix:",

            [

                "Provide a one-off default now (will be set on all existing rows)",

                "Quit, and let me add a default in models.py",

            ]

        )

        if choice == 2:

            sys.exit(3)

        else:

            print("Please enter the default value now, as valid Python")

            print("The datetime module is available, so you can do e.g. datetime.date.today()")

            while True:

                code = input(">>> ")

                if not code:

                    print("Please enter some code, or 'exit' (with no quotes) to exit.")

                elif code == "exit":

                    sys.exit(1)

                else:

                    try:

                        return eval(code, {}, {"datetime": datetime_safe})

                    except (SyntaxError, NameError) as e:

                        print("Invalid input: %s" % e)

                    else:

                        break