[1.7.x] Fixed #22676 -- makemigrations --dry-run should not ask for defaults

Made the fix in InteractiveMigrationQuestioner class code, rather than
MigrationAutodetector, because --dry-run shouldn't affect whether
MigrationAutodetector will detect non-nullable fields, but the
questioner should skip the question and returns a None for default
(since that won't be used anyway) if --dry-run is used.

Backport of ee14961a2a from master

3 files changed, 43 insertions, 0 deletions

diff --git a/tests/migrations/test_commands.py b/tests/migrations/test_commands.py
index 757d69995b..2f78ee27a4 100644
--- a/tests/migrations/test_commands.py
+++ b/tests/migrations/test_commands.py
@@ -6,6 +6,7 @@ import os
 import shutil
 
 from django.apps import apps
+from django.db import models
 from django.core.management import call_command, CommandError
 from django.db.migrations import questioner
 from django.test import override_settings, override_system_checks
@@ -362,3 +363,22 @@ class MakeMigrationsTests(MigrationTestBase):
         self.assertIn("Merging migrations", stdout.getvalue())
         self.assertIn("Branch 0002_second", stdout.getvalue())
         self.assertIn("Branch 0002_conflicting_second", stdout.getvalue())
+
+    @override_system_checks([])
+    @override_settings(MIGRATION_MODULES={"migrations": "migrations.test_migrations_no_default"})
+    def test_makemigrations_dry_run(self):
+        """
+        Ticket #22676 -- `makemigrations --dry-run` should not ask for defaults.
+        """
+
+        class SillyModel(models.Model):
+            silly_field = models.BooleanField(default=False)
+            silly_date = models.DateField()  # Added field without a default
+
+            class Meta:
+                app_label = "migrations"
+
+        stdout = six.StringIO()
+        call_command("makemigrations", "migrations", dry_run=True, stdout=stdout)
+        # Output the expected changes directly, without asking for defaults
+        self.assertIn("Add field silly_date to sillymodel", stdout.getvalue())
diff --git a/tests/migrations/test_migrations_no_default/0001_initial.py b/tests/migrations/test_migrations_no_default/0001_initial.py
new file mode 100644
index 0000000000..c30910e056
--- /dev/null
+++ b/tests/migrations/test_migrations_no_default/0001_initial.py
@@ -0,0 +1,23 @@
+# -*- coding: utf-8 -*-
+from __future__ import unicode_literals
+
+from django.db import models, migrations
+
+
+class Migration(migrations.Migration):
+
+    dependencies = [
+    ]
+
+    operations = [
+        migrations.CreateModel(
+            name='SillyModel',
+            fields=[
+                ('id', models.AutoField(verbose_name='ID', serialize=False, auto_created=True, primary_key=True)),
+                ('silly_field', models.BooleanField(default=False)),
+            ],
+            options={
+            },
+            bases=(models.Model,),
+        ),
+    ]
diff --git a/tests/migrations/test_migrations_no_default/__init__.py b/tests/migrations/test_migrations_no_default/__init__.py
new file mode 100644
index 0000000000..e69de29bb2
--- /dev/null
+++ b/tests/migrations/test_migrations_no_default/__init__.py