gh-86357: argparse: use str() consistently and explicitly to print choices (GH-117766)

Signed-off-by: Jan Chren ~rindeal <dev.rindeal@gmail.com>

Lib/test/test_argparse.py

@@ -16,6 +16,7 @@ import unittest
 import argparse
 import warnings
 
+from enum import StrEnum
 from test.support import captured_stderr
 from test.support import import_helper
 from test.support import os_helper
@@ -985,6 +986,34 @@ class TestDisallowLongAbbreviationAllowsShortGroupingPrefix(ParserTestCase):
     ]
 
 
+class TestStrEnumChoices(TestCase):
+    class Color(StrEnum):
+        RED = "red"
+        GREEN = "green"
+        BLUE = "blue"
+
+    def test_parse_enum_value(self):
+        parser = argparse.ArgumentParser()
+        parser.add_argument('--color', choices=self.Color)
+        args = parser.parse_args(['--color', 'red'])
+        self.assertEqual(args.color, self.Color.RED)
+
+    def test_help_message_contains_enum_choices(self):
+        parser = argparse.ArgumentParser()
+        parser.add_argument('--color', choices=self.Color, help='Choose a color')
+        self.assertIn('[--color {red,green,blue}]', parser.format_usage())
+        self.assertIn('  --color {red,green,blue}', parser.format_help())
+
+    def test_invalid_enum_value_raises_error(self):
+        parser = argparse.ArgumentParser(exit_on_error=False)
+        parser.add_argument('--color', choices=self.Color)
+        self.assertRaisesRegex(
+            argparse.ArgumentError,
+            r"invalid choice: 'yellow' \(choose from red, green, blue\)",
+            parser.parse_args,
+            ['--color', 'yellow'],
+        )
+
 # ================
 # Positional tests
 # ================
@@ -2485,7 +2514,7 @@ class TestAddSubparsers(TestCase):
             parser.parse_args(('baz',))
         self.assertRegex(
             excinfo.exception.stderr,
-            r"error: argument {foo,bar}: invalid choice: 'baz' \(choose from 'foo', 'bar'\)\n$"
+            r"error: argument {foo,bar}: invalid choice: 'baz' \(choose from foo, bar\)\n$"
         )
 
     def test_optional_subparsers(self):