Fix fail_untyped for Dataclasses

CHANGELOG.rst

@@ -48,6 +48,7 @@ v4.19.0 (2022-12-27)
 
 Added
 ^^^^^
+- ``add_dataclass_arguments`` now supports the ``fail_untyped`` parameter
 - ``CLI`` now supports the ``fail_untyped`` and ``parser_class`` parameters.
 - ``bytes`` and ``bytearray`` registered on first use and decodes from standard
   Base64.

jsonargparse/signatures.py

@@ -312,6 +312,7 @@ def _add_signature_parameter(
             kwargs['required'] = True
         is_subclass_typehint = False
         is_final_class_typehint = is_final_class(annotation)
+        is_pure_dataclass_typehint = is_pure_dataclass(annotation)
         dest = (nested_key+'.' if nested_key else '') + name
         args = [dest if is_required and as_positional else '--'+dest]
         if param.origin:
@@ -326,7 +327,7 @@ def _add_signature_parameter(
         if annotation in {str, int, float, bool} or \
            is_subclass(annotation, (str, int, float)) or \
            is_final_class_typehint or \
-           is_pure_dataclass(annotation):
+           is_pure_dataclass_typehint:
             kwargs['type'] = annotation
         elif annotation != inspect_empty:
             try:
@@ -353,7 +354,7 @@ def _add_signature_parameter(
                 'sub_configs': sub_configs,
                 'instantiate': instantiate,
             }
-            if is_final_class_typehint:
+            if is_final_class_typehint or is_pure_dataclass_typehint:
                 kwargs.update(sub_add_kwargs)
             action = group.add_argument(*args, **kwargs)
             action.sub_add_kwargs = sub_add_kwargs
@@ -370,6 +371,7 @@ def add_dataclass_arguments(
         nested_key: str,
         default: Optional[Union[Type, dict]] = None,
         as_group: bool = True,
+        fail_untyped: bool = True,
         **kwargs
     ) -> List[str]:
         """Adds arguments from a dataclass based on its field types and docstrings.
@@ -379,6 +381,7 @@ def add_dataclass_arguments(
             nested_key: Key for nested namespace.
             default: Value for defaults. Must be instance of or kwargs for theclass.
             as_group: Whether arguments should be added to a new argument group.
+            fail_untyped: Whether to raise exception if a required parameter does not have a type.
 
         Returns:
             The list of arguments added.
@@ -413,6 +416,7 @@ def add_dataclass_arguments(
                 nested_key,
                 params[field.name],
                 added_args,
+                fail_untyped=fail_untyped,
                 default=defaults.get(field.name, inspect_empty),
             )
 

jsonargparse_tests/test_signatures.py

@@ -1571,6 +1571,32 @@ class MyDataClass:
         self.assertEqual({'a': 1.2, 'b': 3.4}, cfg['a2'])
 
 
+    def test_dataclass_fail_untyped(self):
+
+        class MyClass:
+            def __init__(self, c1) -> None:
+                self.c1 = c1
+
+        @dataclasses.dataclass
+        class MyDataclass:
+            a1: MyClass
+            a2: str = "a2"
+            a3: str = "a3"
+
+        parser = ArgumentParser(exit_on_error=False)
+        parser.add_argument('--cfg', type=MyDataclass, fail_untyped=False)
+
+        with mock_module(MyDataclass, MyClass) as module:
+            class_path = f'"class_path": "{module}.MyClass"'
+            init_args = '"init_args": {"c1": 1}'
+            cfg = parser.parse_args(['--cfg.a1={'+class_path+', '+init_args+'}'])
+            cfg = parser.instantiate_classes(cfg)
+            self.assertIsInstance(cfg['cfg'], MyDataclass)
+            self.assertIsInstance(cfg['cfg'].a1, MyClass)
+            self.assertIsInstance(cfg['cfg'].a2, str)
+            self.assertIsInstance(cfg['cfg'].a3, str)
+
+
     def test_compose_dataclasses(self):
 
         @dataclasses.dataclass