Fix % for docstrings in bool flags

dcargs/_arguments.py

@@ -195,11 +195,20 @@ def _bool_flags(arg: ArgumentDefinition) -> _ArgumentTransformOutput:
 
     # Populate helptext for boolean flags => don't show default value, which can be
     # confusing.
-    helptext = _docstrings.get_field_docstring(arg.parent_class, arg.field.name)
-    arg = dataclasses.replace(
-        arg,
-        help=helptext if helptext is not None else "",
-    )
+    docstring_help = _docstrings.get_field_docstring(arg.parent_class, arg.field.name)
+    if docstring_help is not None:
+        # Note that the percent symbol needs some extra handling in argparse.
+        # https://stackoverflow.com/questions/21168120/python-argparse-errors-with-in-help-string
+        docstring_help = docstring_help.replace("%", "%%")
+        arg = dataclasses.replace(
+            arg,
+            help=docstring_help,
+        )
+    else:
+        arg = dataclasses.replace(
+            arg,
+            help="",
+        )
 
     if arg.default is None:
         return (

setup.py

@@ -5,7 +5,7 @@
 
 setup(
     name="dcargs",
-    version="0.0.10",
+    version="0.0.11",
     description="Portable, reusable, strongly typed CLIs from dataclass definitions",
     long_description=long_description,
     long_description_content_type="text/markdown",

tests/test_docstrings.py

@@ -73,12 +73,12 @@ class Config:
     assert "  --x INT     An optional variable. (default: None)\n" in helptext
 
 
-def test_helptext_hard_string():
+def test_helptext_hard_bool():
     @dataclasses.dataclass
     class HelptextHardString:
         # fmt: off
-        x: str = (
-            "This docstring may be tougher to parse!"
+        x: bool = (
+            False
         )
         """Helptext. 2% milk."""
         # fmt: on
@@ -91,10 +91,7 @@ class HelptextHardString:
         with contextlib.redirect_stdout(f):
             dcargs.parse(HelptextHardString, args=["--help"])
     helptext = f.getvalue()
-    assert (
-        "--x STR     Helptext. 2% milk. (default: This docstring may be tougher to parse!)\n"
-        in helptext
-    )
+    assert "--x         Helptext. 2% milk.\n" in helptext
 
 
 def test_helptext_with_inheritance():