Fix the check for None type in inspect._get_parser (#96)

Fix the check for `None` type in `inspect._get_parser`

fgpyo/util/inspect.py

@@ -70,6 +70,9 @@ def split_at_given_level(
     return out_vals
 
 
+NoneType = type(None)
+
+
 def _get_parser(
     cls: Type, type_: TypeAlias, parsers: Optional[Dict[type, Callable[[str], Any]]] = None
 ) -> partial:
@@ -226,7 +229,7 @@ def dict_parse(dict_string: str) -> Dict[Any, Any]:
                 return types.make_enum_parser(type_)
             elif types.is_constructible_from_str(type_):
                 return functools.partial(type_)
-            elif isinstance(type_, type(type(None))):
+            elif type_ == NoneType:
                 return functools.partial(types.none_parser)
             elif types.get_origin_type(type_) is Union:
                 return types.make_union_parser(

fgpyo/util/tests/test_inspect.py

@@ -1,6 +1,7 @@
 from typing import Optional
 
 import attr
+import pytest
 
 from fgpyo.util.inspect import attr_from
 from fgpyo.util.inspect import attribute_has_default
@@ -45,3 +46,23 @@ def test_attribute_has_default() -> None:
     assert attribute_has_default(fields_dict["optional_no_default"])
     assert attribute_has_default(fields_dict["optional_with_default_none"])
     assert attribute_has_default(fields_dict["optional_with_default_some"])
+
+
+class Foo:
+    pass
+
+
+@attr.s(auto_attribs=True, frozen=True)
+class Bar:
+    foo: Foo
+
+
+# Test for regression #94 - the call to attr_from succeeds when the check for None type
+# in inspect._get_parser is done incorrectly.
+def test_attr_from_custom_type_without_parser_fails() -> None:
+    with pytest.raises(AssertionError):
+        attr_from(
+            cls=Bar,
+            kwargs={"foo": ""},
+            parsers={},
+        )