gh-148468: Accept string-like help proxies in argparse

Author: Raghu

Lib/argparse.py

@@ -548,6 +548,7 @@ def _get_actions_usage_parts(self, actions, groups):
         return parts, pos_start
 
     def _format_text(self, text):
+        text = str(text)
         if '%(prog)' in text:
             text = text % dict(prog=self._prog)
         text_width = max(self._width - self._current_indent, 11)
@@ -564,6 +565,7 @@ def _apply_text_markup(self, text):
 
         When colors are disabled, backticks are preserved as-is.
         """
+        text = str(text)
         t = self._theme
         if not t.reset:
             return text
@@ -610,9 +612,9 @@ def _format_action(self, action):
         parts = [action_header]
 
         # if there was help for the action, add lines of help text
-        if action.help and action.help.strip():
+        if action.help:
             help_text = self._expand_help(action)
-            if help_text:
+            if help_text.strip():
                 help_lines = self._split_lines(help_text, help_width)
                 parts.append('%*s%s\n' % (indent_first, '', help_lines[0]))
                 for line in help_lines[1:]:
@@ -711,7 +713,7 @@ def _format_args(self, action, default_metavar):
         return result
 
     def _expand_help(self, action):
-        help_string = self._get_help_string(action)
+        help_string = str(self._get_help_string(action))
         if '%' not in help_string:
             return self._apply_text_markup(help_string)
         params = dict(vars(action), prog=self._prog)

Lib/test/test_argparse.py

@@ -7398,6 +7398,19 @@ def setUp(self):
                                      lambda *args, **kwargs: True))
         self.theme = _colorize.get_theme(force_color=True).argparse
 
+    class _LazyStr:
+        def __init__(self, message):
+            self._message = message
+
+        def __str__(self):
+            return self._message
+
+        def __contains__(self, item):
+            return item in self._message
+
+        def __mod__(self, other):
+            return self._message % other
+
     def test_argparse_color(self):
         # Arrange: create a parser with a bit of everything
         parser = argparse.ArgumentParser(
@@ -7736,6 +7749,38 @@ def test_backtick_markup_in_description(self):
         )
         self.assertNotIn("`", help_text)
 
+    def test_backtick_markup_in_description_accepts_string_like_proxy(self):
+        parser = argparse.ArgumentParser(
+            prog='PROG',
+            color=True,
+            description=self._LazyStr(
+                'Run `python myapp` or ``python -m myapp`` to start.'
+            ),
+        )
+
+        prog_extra = self.theme.prog_extra
+        reset = self.theme.reset
+
+        help_text = parser.format_help()
+        self.assertIn(
+            f'Run {prog_extra}python myapp{reset} or '
+            f'{prog_extra}python -m myapp{reset} to start.',
+            help_text,
+        )
+
+    def test_backtick_markup_in_epilog_accepts_string_like_proxy(self):
+        parser = argparse.ArgumentParser(
+            prog='myapp',
+            color=True,
+            epilog=self._LazyStr('Run `%(prog)s --help` for more info.'),
+        )
+
+        prog_extra = self.theme.prog_extra
+        reset = self.theme.reset
+
+        help_text = parser.format_help()
+        self.assertIn(f'{prog_extra}myapp --help{reset}', help_text)
+
     def test_backtick_markup_multiple(self):
         parser = argparse.ArgumentParser(
             prog='PROG',
@@ -7837,6 +7882,34 @@ def test_backtick_markup_in_argument_help_color_disabled(self):
         self.assertIn("set the `foo` value", help_text)
         self.assertNotIn("\x1b[", help_text)
 
+    def test_backtick_markup_in_argument_help_accepts_string_like_proxy(self):
+        parser = argparse.ArgumentParser(prog="PROG", color=True)
+        parser.add_argument(
+            "--foo", help=self._LazyStr("set the `foo` value")
+        )
+
+        prog_extra = self.theme.prog_extra
+        reset = self.theme.reset
+
+        help_text = parser.format_help()
+        self.assertIn(f"set the {prog_extra}foo{reset} value", help_text)
+
+    def test_argument_help_interpolation_accepts_string_like_proxy(self):
+        parser = argparse.ArgumentParser(prog="PROG", color=True)
+        parser.add_argument(
+            "--foo",
+            default="bar",
+            help=self._LazyStr("set `foo` (default: %(default)s)"),
+        )
+
+        prog_extra = self.theme.prog_extra
+        interp = self.theme.interpolated_value
+        reset = self.theme.reset
+
+        help_text = parser.format_help()
+        self.assertIn(f"set {prog_extra}foo{reset}", help_text)
+        self.assertIn(f"default: {interp}bar{reset}", help_text)
+
     def test_help_with_format_specifiers(self):
         # GH-142950: format specifiers like %x should work with color=True
         parser = argparse.ArgumentParser(prog='PROG', color=True)

Misc/NEWS.d/next/Library/2026-05-22-17-53-01.gh-issue-148468.o5fZ3K.rst

@@ -0,0 +1,3 @@
+Fix a regression in :mod:`argparse` so colorized help formatting once again
+accepts string-like proxy objects for descriptions, epilogs, and argument
+help text.