feat: add support for python 3.10+ optional types

Author: cuinixam

src/py_app_dev/core/cmd_line.py

@@ -1,4 +1,5 @@
 import dataclasses
+import types
 from abc import ABC, abstractmethod
 from argparse import ArgumentError, ArgumentParser, Namespace
 from typing import Any, Union, get_args
@@ -87,7 +88,13 @@ def add_command(self, command: Command) -> "CommandLineHandlerBuilder":
 
 
 def is_type_optional(some_type: Any) -> bool:
-    return hasattr(some_type, "__origin__") and some_type.__origin__ is Union and type(None) in some_type.__args__
+    # Handle old typing.Union syntax (Optional[T] or Union[T, None])
+    if hasattr(some_type, "__origin__") and some_type.__origin__ is Union and type(None) in some_type.__args__:
+        return True
+    # Handle new union syntax (T | None) - Python 3.10+
+    if isinstance(some_type, types.UnionType) and type(None) in some_type.__args__:
+        return True
+    return False
 
 
 def is_type_list(some_type: Any) -> bool:

tests/test_cmd_line.py

@@ -74,7 +74,7 @@ def test_duplicate_commands():
 class MyConfigDataclass:
     my_first_arg: Path = field(metadata={"help": "Some help for arg1."})
     arg: str = field(default="value1", metadata={"help": "Some help for arg1."})
-    opt_arg: str | None = field(default=None, metadata={"help": "Some help for arg1."})
+    opt_arg: Optional[str] = field(default=None, metadata={"help": "Some help for arg1."})
     opt_arg_bool: bool | None = field(
         default=False,
         metadata={
@@ -88,6 +88,10 @@ def test_is_type_optional():
     assert is_type_optional(Optional[str])
     assert not is_type_optional(str)
     assert is_type_optional(Union[Path | None, str])
+    # Test modern union syntax (Python 3.10+)
+    assert is_type_optional(Path | None)
+    assert is_type_optional(str | None)
+    assert not is_type_optional(Path | str)  # Union without None should not be optional
     assert not is_type_optional(Union[Path, str])
 
 
@@ -138,6 +142,45 @@ def test_register_optional_path_arguments():
     }
 
 
+@dataclass
+class ClassWithModernUnionTypes:
+    """Test class with various modern union syntax optional fields."""
+
+    required_path: Path = field(metadata={"help": "Required path."})
+    optional_path: Path | None = field(default=None, metadata={"help": "Optional path."})
+    optional_str: str | None = field(default=None, metadata={"help": "Optional string."})
+    optional_int: int | None = field(default=None, metadata={"help": "Optional integer."})
+    optional_bool: bool | None = field(default=None, metadata={"help": "Optional boolean."})
+
+
+def test_register_modern_union_optional_arguments():
+    """Test that modern union syntax (T | None) works correctly."""
+    parser = ArgumentParser()
+    register_arguments_for_config_dataclass(parser, ClassWithModernUnionTypes)
+
+    # Test with all arguments provided
+    args = parser.parse_args(
+        ["--required-path", "required/path", "--optional-path", "optional/path", "--optional-str", "test_string", "--optional-int", "42", "--optional-bool", "true"]
+    )
+    assert vars(args) == {
+        "required_path": Path("required/path"),
+        "optional_path": Path("optional/path"),
+        "optional_str": "test_string",
+        "optional_int": 42,
+        "optional_bool": True,
+    }
+
+    # Test with only required arguments
+    args = parser.parse_args(["--required-path", "required/path"])
+    assert vars(args) == {
+        "required_path": Path("required/path"),
+        "optional_path": None,
+        "optional_str": None,
+        "optional_int": None,
+        "optional_bool": None,
+    }
+
+
 @dataclass
 class ClassWithListArgument:
     my_paths: list[Path] = field(metadata={"help": "List of paths"})