#137 Add get_repr_type

Author: astropenguin

tests/test_typing.py

@@ -1,10 +1,10 @@
 # standard library
-from typing import Any, Tuple
+from typing import Any, Optional, Tuple, Union
 
 
 # third-party packages
 from pytest import mark
-from typing_extensions import Literal
+from typing_extensions import Annotated, Literal
 
 
 # submodules
@@ -17,6 +17,7 @@
     get_dims,
     get_dtype,
     get_field_type,
+    get_repr_type,
 )
 
 
@@ -57,6 +58,13 @@
     (Name[Any], "name"),
 ]
 
+testdata_repr_type = [
+    (int, int),
+    (Annotated[int, "annotation"], int),
+    (Union[int, float], int),
+    (Optional[int], int),
+]
+
 
 # test functions
 @mark.parametrize("type_, dims", testdata_dims)
@@ -72,3 +80,8 @@ def test_get_dtype(type_: Any, dtype: Any) -> None:
 @mark.parametrize("type_, field_type", testdata_field_type)
 def test_get_field_type(type_: Any, field_type: Any) -> None:
     assert get_field_type(type_).value == field_type
+
+
+@mark.parametrize("type_, repr_type", testdata_repr_type)
+def test_get_repr_type(type_: Any, repr_type: Any) -> None:
+    assert get_repr_type(type_) == repr_type

xarray_dataclasses/typing.py

@@ -344,6 +344,30 @@ def get_inner(hint: Any, *indexes: int) -> Any:
     return get_inner(get_args(hint)[index], *indexes)
 
 
+def get_repr_type(type_: Any) -> Any:
+    """Parse a type and return an representative type.
+
+    Example:
+        All of the following expressions will be ``True``::
+
+            get_repr_type(A) == A
+            get_repr_type(Annotated[A, ...]) == A
+            get_repr_type(Union[A, B, ...]) == A
+            get_repr_type(Optional[A]) == A
+
+    """
+
+    class Temporary:
+        __annotations__ = dict(type=type_)
+
+    unannotated = get_type_hints(Temporary)["type"]
+
+    if get_origin(unannotated) is Union:
+        return get_args(unannotated)[0]
+
+    return unannotated
+
+
 def is_str_literal(hint: Any) -> bool:
     """Check if a type hint is Literal[str]."""
     args: Any = get_args(hint)