fix: pep 695 named alias union fix

src/latch_data_validation/data_validation.py

@@ -28,7 +28,7 @@
     Sequence as SequenceOld,  # pyright: ignore[reportDeprecated]
 )
 
-from typing_extensions import NotRequired, Required, TypeForm, override
+from typing_extensions import NotRequired, Required, TypeAliasType, TypeForm, override
 
 __all__ = []
 
@@ -189,6 +189,18 @@ def _untraced_validate(
     x: JsonValue, cls: TypeForm[T], *, type_vars: dict[int, TypeForm[object]]
 ) -> T:
     # todo(maximsmol): improve error messages with generics
+    alias_origin = get_origin(cls)
+    if isinstance(alias_origin, TypeAliasType):
+        type_vars2 = {**type_vars}
+        for parameter, argument in zip(
+            alias_origin.__type_params__, get_args(cls), strict=True
+        ):
+            type_vars2[id(parameter)] = argument
+        return _untraced_validate(x, alias_origin.__value__, type_vars=type_vars2)
+
+    if isinstance(cls, TypeAliasType):
+        return _untraced_validate(x, cls.__value__, type_vars=type_vars)
+
     if isinstance(cls, TypeVar):
         ref = type_vars.get(id(cls))
         if ref is None:

tests/test_basic.py

@@ -1,10 +1,11 @@
 import typing
 from collections.abc import Mapping, Sequence
+from dataclasses import dataclass
 from enum import Enum
 
 import pytest
 from syrupy.extensions.json import JSONSnapshotExtension
-from typing_extensions import NotRequired, Required, TypedDict, TypeVar
+from typing_extensions import NotRequired, Required, TypeAliasType, TypedDict, TypeVar
 
 BrokenJsonArray: typing.TypeAlias = typing.Sequence["BrokenJsonValue"]  # pyright: ignore[reportDeprecated]
 BrokenJsonObject: typing.TypeAlias = typing.Mapping[str, "BrokenJsonValue"]  # pyright: ignore[reportDeprecated]
@@ -18,6 +19,19 @@
     BrokenJsonObject2 | BrokenJsonArray2 | str | int | float | bool | None
 )
 
+TestWaitingReason = TypeAliasType(
+    "TestWaitingReason", typing.Literal["workspace_capacity", "taiga_rate_limited"]
+)
+
+
+@dataclass
+class AliasedRequest:
+    waiting_reason: TestWaitingReason | None
+
+
+AliasT = TypeVar("AliasT")
+TestBox = TypeAliasType("TestBox", list[AliasT], type_params=(AliasT,))
+
 
 from latch_data_validation.data_validation import (
     DataValidationError,
@@ -157,6 +171,24 @@ class Test:
     assert x.c.a == 2
 
 
+def test_type_alias() -> None:
+    assert validate(
+        {"waiting_reason": "workspace_capacity"}, AliasedRequest
+    ) == AliasedRequest(waiting_reason="workspace_capacity")
+    assert validate({"waiting_reason": None}, AliasedRequest) == AliasedRequest(
+        waiting_reason=None
+    )
+
+    with pytest.raises(DataValidationError):
+        _ = validate({"waiting_reason": "unknown"}, AliasedRequest)
+
+
+def test_generic_type_alias() -> None:
+    assert validate([1, 2], TestBox[int]) == [1, 2]
+    with pytest.raises(DataValidationError):
+        _ = validate([1, "two"], TestBox[int])
+
+
 def test_forwardref(snapshot_json) -> None:
     _ = validate({"a": 123}, JsonValue)