Loosen ParserMethod typing (#188)

* Loosen ParserMethod typing

* Run mypy against examples/ dir

* Update changelog

Co-authored-by: Steven Loria <sloria1@gmail.com>

Author: hukkinj1

CHANGELOG.md

@@ -8,6 +8,11 @@ Features:
   ([#184](https://github.com/sloria/environs/pull/184)).
   Thanks [tomgrin10](https://github.com/tomgrin10?) for the PR.
 
+Bug fixes:
+
+- Loosen `ParserMethod` typing ([#186 (comment)](https://github.com/sloria/environs/issues/186#issuecomment-723163520)).
+  Thanks [hukkinj1](https://github.com/hukkinj1) for the PR.
+
 Other changes:
 
 - When using deferred validation (`eager=False`), parser methods return `None`

environs/__init__.py

@@ -30,7 +30,7 @@
 Subcast = typing.Union[typing.Type, typing.Callable[..., _T]]
 FieldType = typing.Type[ma.fields.Field]
 FieldOrFactory = typing.Union[FieldType, FieldFactory]
-ParserMethod = typing.Callable[..., typing.Optional[_T]]
+ParserMethod = typing.Callable
 
 
 _EXPANDED_VAR_PATTERN = re.compile(r"(?<!\\)\$\{([A-Za-z0-9_]+)(:-[^\}:]*)?\}")