Don't show '(default: None)' for required arguments without a default

simple_parsing/help_formatter.py

@@ -79,7 +79,12 @@ def _get_metavar_for_type(self, t: type) -> str:
         return get_metavar(t) or str(t)
 
     def _get_help_string(self, action: Action) -> Optional[str]:
-        help = super()._get_help_string(action=action)
+        if action.required and action.default is None:
+            # A required argument with no default has no default to show. argparse's
+            # ArgumentDefaultsHelpFormatter would still append "(default: None)".
+            help = argparse.HelpFormatter._get_help_string(self, action=action)
+        else:
+            help = super()._get_help_string(action=action)
         if help is not None:
             help = help.replace(TEMPORARY_TOKEN, "")
         return help

test/test_help_required_default.py

@@ -0,0 +1,19 @@
+from dataclasses import dataclass
+
+from simple_parsing import ArgumentParser
+
+
+@dataclass
+class Options:
+    list_items: list[str]  # SOMETHING
+
+
+def test_required_field_without_default_does_not_show_default_none(capsys):
+    parser = ArgumentParser(add_option_string_dash_variants=True)
+    parser.add_arguments(Options, dest="options")
+
+    parser.print_help()
+    help_text = capsys.readouterr().out
+
+    assert "SOMETHING" in help_text
+    assert "(default: None)" not in help_text

test/test_issue_48.py

@@ -39,11 +39,11 @@ def test_issue_48():
             -s str, --start_date str
                                     Start date from which to collect data about base
                                     users. Input in iso format (YYYY-MM-DD). The date is
-                                    included in the data (default: None)
+                                    included in the data
             -e str, --end_date str
                                     End date for collecting base users. Input in iso
                                     format (YYYY-MM-DD). The date is included in the data.
-                                    Should not be before `start_date` (default: None)
+                                    Should not be before `start_date`
             """
         ),
     )