- Added automatic Optional for arguments with default None #30.

Author: mauvilsa

CHANGELOG.rst

@@ -9,6 +9,14 @@ follow `Semantic Versioning <https://semver.org/>`_
 only be introduced in major versions with advance notice in the **Deprecated**
 section of releases.
 
+v3.X.X (YYYY-MM-DD)
+-------------------
+
+Added
+^^^^^
+- Automatic Optional for arguments with default None #30.
+
+
 v3.1.0 (2020-12-09)
 -------------------
 

jsonargparse/signatures.py

@@ -6,6 +6,7 @@
 
 from .util import _issubclass
 from .actions import ActionEnum
+from .typing import is_optional
 from .jsonschema import ActionJsonSchema
 from .optionals import docstring_parser_support, import_docstring_parse, dataclasses_support, import_dataclasses
 
@@ -247,6 +248,8 @@ def update_has_args_kwargs(base, has_args=True, has_kwargs=True):
                 kwargs = {'help': doc_params.get(name)}
                 if not is_required:
                     kwargs['default'] = default
+                    if default is None and not is_optional(annotation, object):
+                        annotation = Optional[annotation]
                 elif not as_positional:
                     kwargs['required'] = True
                 if annotation in {str, int, float, bool} or \

jsonargparse_tests/signatures_tests.py

@@ -386,6 +386,17 @@ def __init__(self, c1: Optional[Class1]):
         self.assertEqual(2.3, cfg.c1.a2)
 
 
+    def test_implicit_optional(self):
+
+        def func(a1: int = None):
+            return a1
+
+        parser = ArgumentParser(error_handler=None)
+        parser.add_function_arguments(func)
+
+        self.assertIsNone(parser.parse_args(['--a1=null']).a1)
+
+
     @unittest.skipIf(not docstring_parser_support, 'docstring-parser package is required')
     def test_docstring_parse_fail(self):