feat: Add support for identifying and stripping python 3.12 explicit type aliases. (#49)

Author: DanCardin

.github/workflows/ci.yml

@@ -156,7 +156,7 @@ jobs:
           echo "${{ github.event.number }}" > .pr_number
 
       - name: Upload artifact
-        uses: actions/upload-artifact@v3
+        uses: actions/upload-artifact@v4
         with:
           name: docs-preview
           path: |

pyproject.toml

@@ -38,7 +38,7 @@ classifiers = [
     "Intended Audience :: Developers",
 ]
 name = "type-lens"
-version = "0.2.4"
+version = "0.2.5"
 description = "type-lens is a Python template project designed to simplify the setup of a new project."
 readme = "README.md"
 license = { text = "MIT" }

tests/test_type_view.py

@@ -426,3 +426,37 @@ def test_fallback_origin() -> None:
 
     if sys.version_info >= (3, 9):
         assert TypeView(set[bool]).fallback_origin == set
+
+
+@pytest.mark.skipif(sys.version_info < (3, 12), reason="Requires Python 3.12 or higher for TypeAliasType")
+def test_is_type_alias() -> None:
+    from typing import TypeAliasType  # type: ignore[attr-defined]
+
+    Foo = TypeAliasType("Foo", int)  # pyright: ignore
+    assert TypeView(Foo).is_type_alias is True  # pyright: ignore
+    assert TypeView(int).is_type_alias is False
+
+
+def test_is_type_alias_extensions() -> None:
+    from typing_extensions import TypeAliasType
+
+    Foo = TypeAliasType("Foo", int)  # pyright: ignore
+    assert TypeView(Foo).is_type_alias is True
+    assert TypeView(int).is_type_alias is False
+
+
+@pytest.mark.skipif(sys.version_info < (3, 12), reason="Requires Python 3.12 or higher for TypeAliasType")
+def test_strip_type_alias() -> None:
+    from typing import TypeAliasType  # type: ignore[attr-defined]
+
+    Foo = TypeAliasType("Foo", int)  # pyright: ignore
+    assert TypeView(Foo).strip_type_alias() == TypeView(int)  # pyright: ignore
+    assert TypeView(int).strip_type_alias() == TypeView(int)
+
+
+def test_strip_type_alias_extensions() -> None:
+    from typing_extensions import TypeAliasType
+
+    Foo = TypeAliasType("Foo", int)  # pyright: ignore
+    assert TypeView(Foo).strip_type_alias() == TypeView(int)
+    assert TypeView(int).strip_type_alias() == TypeView(int)

type_lens/type_view.py

@@ -1,5 +1,7 @@
 from __future__ import annotations
 
+import sys
+import typing
 from collections import abc
 from collections.abc import Collection, Mapping
 from typing import (
@@ -14,6 +16,7 @@
     _SpecialForm,  # pyright: ignore[reportPrivateUsage]
 )
 
+import typing_extensions
 from typing_extensions import Annotated, NotRequired, Required, get_args, get_origin
 from typing_extensions import Literal as ExtensionsLiteral
 
@@ -204,6 +207,19 @@ def is_variadic_tuple(self) -> bool:
         """
         return self.is_tuple and len(self.args) == 2 and self.args[1] == ...  # pyright: ignore
 
+    if sys.version_info < (3, 12):
+
+        @property
+        def is_type_alias(self) -> bool:
+            """Whether the annotation is a new-style `type Type = ...` alias or not."""
+            return _is_typing_extensins_type_alias(self)
+    else:
+
+        @property
+        def is_type_alias(self) -> bool:
+            """Whether the annotation is a new-style `type Type = ...` alias or not."""
+            return isinstance(self.annotation, typing.TypeAliasType) or _is_typing_extensins_type_alias(self)
+
     @property
     def safe_generic_origin(self) -> Any:
         """A type, safe to be used as a generic type across all supported Python versions.
@@ -260,6 +276,7 @@ def is_subclass_of(self, typ: Any | tuple[Any, ...], /) -> bool:
         return isinstance(self.fallback_origin, type) and issubclass(self.fallback_origin, typ)
 
     def strip_optional(self) -> TypeView[Any]:
+        """Remove the "Optional" component of an `Optional[T]` or `Union[T, None]` type."""
         if not self.is_optional:
             return self
 
@@ -269,3 +286,21 @@ def strip_optional(self) -> TypeView[Any]:
         args = tuple(a for a in self.args if a is not NoneType)
         non_optional = Union[args]  # type: ignore[valid-type]
         return TypeView(non_optional)
+
+    def strip_type_alias(self) -> TypeView[Any]:
+        """Remove the type alias from a `type Type = T` type alias.
+
+        Examples:
+            >>> type Foo = int
+            >>> TypeAlias(Foo).strip_type_alias()
+            TypeView(int)
+        """
+        if not self.is_type_alias:
+            return self
+        return TypeView(self.annotation.__value__)
+
+
+def _is_typing_extensins_type_alias(type_view: TypeView[Any]) -> bool:
+    if hasattr(typing_extensions, "TypeAliasType"):
+        return isinstance(type_view.annotation, typing_extensions.TypeAliasType)
+    return False