Better naming, and prompt for NOT NULL field addition

django/db/migrations/autodetector.py

@@ -1,4 +1,6 @@
 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
@@ -66,12 +68,16 @@ class MigrationAutodetector(object):
             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
@@ -180,6 +186,10 @@ class MigrationAutodetector(object):
                 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"
@@ -209,6 +219,11 @@ class MigrationQuestioner(object):
         "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):
 
@@ -221,7 +236,22 @@ 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"):
@@ -231,3 +261,32 @@ class InteractiveMigrationQuestioner(MigrationQuestioner):
             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