Refs #29026 -- Allowed customizing InteractiveMigrationQuestioner's prompt destination.

Previously, the questioner did not obey the value of stdout provided
to the command.

4 files changed, 74 insertions, 57 deletions

diff --git a/django/core/management/commands/makemigrations.py b/django/core/management/commands/makemigrations.py
index 9077660467..4d26bfe278 100644
--- a/django/core/management/commands/makemigrations.py
+++ b/django/core/management/commands/makemigrations.py
@@ -144,7 +144,11 @@ class Command(BaseCommand):
             return self.handle_merge(loader, conflicts)
 
         if self.interactive:
-            questioner = InteractiveMigrationQuestioner(specified_apps=app_labels, dry_run=self.dry_run)
+            questioner = InteractiveMigrationQuestioner(
+                specified_apps=app_labels,
+                dry_run=self.dry_run,
+                prompt_output=self.stdout,
+            )
         else:
             questioner = NonInteractiveMigrationQuestioner(
                 specified_apps=app_labels,
@@ -250,7 +254,7 @@ class Command(BaseCommand):
         if it's safe; otherwise, advises on how to fix it.
         """
         if self.interactive:
-            questioner = InteractiveMigrationQuestioner()
+            questioner = InteractiveMigrationQuestioner(prompt_output=self.stdout)
         else:
             questioner = MigrationQuestioner(defaults={'ask_merge': True})
 
diff --git a/django/db/migrations/questioner.py b/django/db/migrations/questioner.py
index 17883ca76c..3460e2b3ab 100644
--- a/django/db/migrations/questioner.py
+++ b/django/db/migrations/questioner.py
@@ -4,6 +4,7 @@ import os
 import sys
 
 from django.apps import apps
+from django.core.management.base import OutputWrapper
 from django.db.models import NOT_PROVIDED
 from django.utils import timezone
 from django.utils.version import get_docs_version
@@ -87,20 +88,26 @@ class MigrationQuestioner:
 
 
 class InteractiveMigrationQuestioner(MigrationQuestioner):
+    def __init__(self, defaults=None, specified_apps=None, dry_run=None, prompt_output=None):
+        super().__init__(defaults=defaults, specified_apps=specified_apps, dry_run=dry_run)
+        self.prompt_output = prompt_output or OutputWrapper(sys.stdout)
 
     def _boolean_input(self, question, default=None):
-        result = input("%s " % question)
+        self.prompt_output.write(f'{question} ', ending='')
+        result = input()
         if not result and default is not None:
             return default
         while not result or result[0].lower() not in "yn":
-            result = input("Please answer yes or no: ")
+            self.prompt_output.write('Please answer yes or no: ', ending='')
+            result = input()
         return result[0].lower() == "y"
 
     def _choice_input(self, question, choices):
-        print(question)
+        self.prompt_output.write(f'{question}')
         for i, choice in enumerate(choices):
-            print(" %s) %s" % (i + 1, choice))
-        result = input("Select an option: ")
+            self.prompt_output.write(' %s) %s' % (i + 1, choice))
+        self.prompt_output.write('Select an option: ', ending='')
+        result = input()
         while True:
             try:
                 value = int(result)
@@ -109,7 +116,8 @@ class InteractiveMigrationQuestioner(MigrationQuestioner):
             else:
                 if 0 < value <= len(choices):
                     return value
-            result = input("Please select a valid option: ")
+            self.prompt_output.write('Please select a valid option: ', ending='')
+            result = input()
 
     def _ask_default(self, default=''):
         """
@@ -119,34 +127,35 @@ class InteractiveMigrationQuestioner(MigrationQuestioner):
         string) which will be shown to the user and used as the return value
         if the user doesn't provide any other input.
         """
-        print('Please enter the default value as valid Python.')
+        self.prompt_output.write('Please enter the default value as valid Python.')
         if default:
-            print(
+            self.prompt_output.write(
                 f"Accept the default '{default}' by pressing 'Enter' or "
                 f"provide another value."
             )
-        print(
+        self.prompt_output.write(
             'The datetime and django.utils.timezone modules are available, so '
             'it is possible to provide e.g. timezone.now as a value.'
         )
-        print("Type 'exit' to exit this prompt")
+        self.prompt_output.write("Type 'exit' to exit this prompt")
         while True:
             if default:
                 prompt = "[default: {}] >>> ".format(default)
             else:
                 prompt = ">>> "
-            code = input(prompt)
+            self.prompt_output.write(prompt, ending='')
+            code = input()
             if not code and default:
                 code = default
             if not code:
-                print("Please enter some code, or 'exit' (without quotes) to exit.")
+                self.prompt_output.write("Please enter some code, or 'exit' (without quotes) to exit.")
             elif code == "exit":
                 sys.exit(1)
             else:
                 try:
                     return eval(code, {}, {'datetime': datetime, 'timezone': timezone})
                 except (SyntaxError, NameError) as e:
-                    print("Invalid input: %s" % e)
+                    self.prompt_output.write('Invalid input: %s' % e)
 
     def ask_not_null_addition(self, field_name, model_name):
         """Adding a NOT NULL field to a model."""
diff --git a/tests/migrations/test_commands.py b/tests/migrations/test_commands.py
index bf78b60a85..ef5db241d6 100644
--- a/tests/migrations/test_commands.py
+++ b/tests/migrations/test_commands.py
@@ -1304,7 +1304,15 @@ class MakeMigrationsTests(MigrationTestBase):
         # Monkeypatch interactive questioner to auto reject
         with mock.patch('builtins.input', mock.Mock(return_value='N')):
             with self.temporary_migration_module(module="migrations.test_migrations_conflict") as migration_dir:
-                call_command("makemigrations", "migrations", name="merge", merge=True, interactive=True, verbosity=0)
+                with captured_stdout():
+                    call_command(
+                        'makemigrations',
+                        'migrations',
+                        name='merge',
+                        merge=True,
+                        interactive=True,
+                        verbosity=0,
+                    )
                 merge_file = os.path.join(migration_dir, '0003_merge.py')
                 self.assertFalse(os.path.exists(merge_file))
 
@@ -1766,6 +1774,10 @@ class MakeMigrationsTests(MigrationTestBase):
                 '    - remove field silly_field from author\n'
                 '    - add field rating to author\n'
                 '    - create model book\n'
+                '\n'
+                'merging will only work if the operations printed above do not conflict\n'
+                'with each other (working on different fields or models)\n'
+                'should these migration branches be merged? [y/n] '
             )
 
     def test_makemigrations_with_custom_name(self):
@@ -1886,30 +1898,25 @@ class MakeMigrationsTests(MigrationTestBase):
             "It is impossible to add the field 'creation_date' with "
             "'auto_now_add=True' to entry without providing a default. This "
             "is because the database needs something to populate existing "
-            "rows.\n\n"
+            "rows.\n"
             " 1) Provide a one-off default now which will be set on all "
             "existing rows\n"
             " 2) Quit and manually define a default value in models.py."
         )
         # Monkeypatch interactive questioner to auto accept
-        with mock.patch('django.db.migrations.questioner.sys.stdout', new_callable=io.StringIO) as prompt_stdout:
-            out = io.StringIO()
-            with self.temporary_migration_module(module='migrations.test_auto_now_add'):
-                call_command('makemigrations', 'migrations', interactive=True, stdout=out)
-            output = out.getvalue()
-            prompt_output = prompt_stdout.getvalue()
-            self.assertIn(input_msg, prompt_output)
-            self.assertIn(
-                'Please enter the default value as valid Python.',
-                prompt_output,
-            )
-            self.assertIn(
-                "Accept the default 'timezone.now' by pressing 'Enter' or "
-                "provide another value.",
-                prompt_output,
-            )
-            self.assertIn("Type 'exit' to exit this prompt", prompt_output)
-            self.assertIn("Add field creation_date to entry", output)
+        prompt_stdout = io.StringIO()
+        with self.temporary_migration_module(module='migrations.test_auto_now_add'):
+            call_command('makemigrations', 'migrations', interactive=True, stdout=prompt_stdout)
+        prompt_output = prompt_stdout.getvalue()
+        self.assertIn(input_msg, prompt_output)
+        self.assertIn('Please enter the default value as valid Python.', prompt_output)
+        self.assertIn(
+            "Accept the default 'timezone.now' by pressing 'Enter' or provide "
+            "another value.",
+            prompt_output,
+        )
+        self.assertIn("Type 'exit' to exit this prompt", prompt_output)
+        self.assertIn("Add field creation_date to entry", prompt_output)
 
     @mock.patch('builtins.input', return_value='2')
     def test_makemigrations_auto_now_add_interactive_quit(self, mock_input):
@@ -1960,7 +1967,7 @@ class MakeMigrationsTests(MigrationTestBase):
         input_msg = (
             f'Callable default on unique field book.created will not generate '
             f'unique values upon migrating.\n'
-            f'Please choose how to proceed:\n\n'
+            f'Please choose how to proceed:\n'
             f' 1) Continue making this migration as the first step in writing '
             f'a manual migration to generate unique values described here: '
             f'https://docs.djangoproject.com/en/{version}/howto/'
diff --git a/tests/migrations/test_questioner.py b/tests/migrations/test_questioner.py
index c9690d0b99..472a3f248f 100644
--- a/tests/migrations/test_questioner.py
+++ b/tests/migrations/test_questioner.py
@@ -1,12 +1,14 @@
 import datetime
+from io import StringIO
 from unittest import mock
 
+from django.core.management.base import OutputWrapper
 from django.db.migrations.questioner import (
     InteractiveMigrationQuestioner, MigrationQuestioner,
 )
 from django.db.models import NOT_PROVIDED
 from django.test import SimpleTestCase
-from django.test.utils import captured_stdout, override_settings
+from django.test.utils import override_settings
 
 
 class QuestionerTests(SimpleTestCase):
@@ -24,65 +26,60 @@ class QuestionerTests(SimpleTestCase):
 
     @mock.patch('builtins.input', return_value='2')
     def test_ask_not_null_alteration_not_provided(self, mock):
-        questioner = InteractiveMigrationQuestioner()
-        with captured_stdout():
-            question = questioner.ask_not_null_alteration('field_name', 'model_name')
+        questioner = InteractiveMigrationQuestioner(prompt_output=OutputWrapper(StringIO()))
+        question = questioner.ask_not_null_alteration('field_name', 'model_name')
         self.assertEqual(question, NOT_PROVIDED)
 
 
 class QuestionerHelperMethodsTests(SimpleTestCase):
-    questioner = InteractiveMigrationQuestioner()
+    def setUp(self):
+        self.prompt = OutputWrapper(StringIO())
+        self.questioner = InteractiveMigrationQuestioner(prompt_output=self.prompt)
 
     @mock.patch('builtins.input', return_value='datetime.timedelta(days=1)')
     def test_questioner_default_timedelta(self, mock_input):
-        questioner = InteractiveMigrationQuestioner()
-        with captured_stdout():
-            value = questioner._ask_default()
+        value = self.questioner._ask_default()
         self.assertEqual(value, datetime.timedelta(days=1))
 
     @mock.patch('builtins.input', return_value='')
     def test_questioner_default_no_user_entry(self, mock_input):
-        with captured_stdout():
-            value = self.questioner._ask_default(default='datetime.timedelta(days=1)')
+        value = self.questioner._ask_default(default='datetime.timedelta(days=1)')
         self.assertEqual(value, datetime.timedelta(days=1))
 
     @mock.patch('builtins.input', side_effect=['', 'exit'])
     def test_questioner_no_default_no_user_entry(self, mock_input):
-        with captured_stdout() as stdout, self.assertRaises(SystemExit):
+        with self.assertRaises(SystemExit):
             self.questioner._ask_default()
         self.assertIn(
             "Please enter some code, or 'exit' (without quotes) to exit.",
-            stdout.getvalue(),
+            self.prompt.getvalue(),
         )
 
     @mock.patch('builtins.input', side_effect=['bad code', 'exit'])
     def test_questioner_no_default_bad_user_entry_code(self, mock_input):
-        with captured_stdout() as stdout, self.assertRaises(SystemExit):
+        with self.assertRaises(SystemExit):
             self.questioner._ask_default()
-        self.assertIn('Invalid input: ', stdout.getvalue())
+        self.assertIn('Invalid input: ', self.prompt.getvalue())
 
     @mock.patch('builtins.input', side_effect=['', 'n'])
     def test_questioner_no_default_no_user_entry_boolean(self, mock_input):
-        with captured_stdout():
-            value = self.questioner._boolean_input('Proceed?')
+        value = self.questioner._boolean_input('Proceed?')
         self.assertIs(value, False)
 
     @mock.patch('builtins.input', return_value='')
     def test_questioner_default_no_user_entry_boolean(self, mock_input):
-        with captured_stdout():
-            value = self.questioner._boolean_input('Proceed?', default=True)
+        value = self.questioner._boolean_input('Proceed?', default=True)
         self.assertIs(value, True)
 
     @mock.patch('builtins.input', side_effect=[10, 'garbage', 1])
     def test_questioner_bad_user_choice(self, mock_input):
         question = 'Make a choice:'
-        with captured_stdout() as stdout:
-            value = self.questioner._choice_input(question, choices='abc')
+        value = self.questioner._choice_input(question, choices='abc')
         expected_msg = (
             f'{question}\n'
             f' 1) a\n'
             f' 2) b\n'
             f' 3) c\n'
         )
-        self.assertIn(expected_msg, stdout.getvalue())
+        self.assertIn(expected_msg, self.prompt.getvalue())
         self.assertEqual(value, 1)