done

lib/python3.11/site-packages/narwhals/_typing_compat.py

@@ -0,0 +1,86 @@
+"""Backward compatibility for newer/less buggy typing features.
+
+## Important
+Import from here to avoid introducing a runtime dependency on [`typing_extensions`]
+
+## Notes
+- `TypeVar` defaults
+  - https://typing.python.org/en/latest/spec/generics.html#type-parameter-defaults
+  - https://peps.python.org/pep-0696/
+- `@deprecated`
+  - https://docs.python.org/3/library/warnings.html#warnings.deprecated
+  - https://typing.python.org/en/latest/spec/directives.html#deprecated
+  - https://peps.python.org/pep-0702/
+
+[`typing_extensions`]: https://github.com/python/typing_extensions
+"""
+
+from __future__ import annotations
+
+# ruff: noqa: ARG001, ANN202, N802
+import sys
+from typing import TYPE_CHECKING, Any
+
+if TYPE_CHECKING:
+    from typing import Callable
+
+    if sys.version_info >= (3, 13):
+        from typing import TypeVar
+        from warnings import deprecated
+    else:
+        from typing_extensions import TypeVar, deprecated
+
+    if sys.version_info >= (3, 11):
+        from typing import Never, assert_never
+    else:
+        from typing_extensions import Never, assert_never
+
+    _Fn = TypeVar("_Fn", bound=Callable[..., Any])
+
+
+else:  # pragma: no cover
+    if sys.version_info >= (3, 13):
+        from typing import TypeVar
+        from warnings import deprecated
+    else:
+        from typing import TypeVar as _TypeVar
+
+        def TypeVar(
+            name: str,
+            *constraints: Any,
+            bound: Any | None = None,
+            covariant: bool = False,
+            contravariant: bool = False,
+            **kwds: Any,
+        ):
+            return _TypeVar(
+                name,
+                *constraints,
+                bound=bound,
+                covariant=covariant,
+                contravariant=contravariant,
+            )
+
+        def deprecated(message: str, /) -> Callable[[_Fn], _Fn]:
+            def wrapper(func: _Fn, /) -> _Fn:
+                return func
+
+            return wrapper
+
+    _ASSERT_NEVER_REPR_MAX_LENGTH = 100
+    _BUG_URL = (
+        "https://github.com/narwhals-dev/narwhals/issues/new?template=bug_report.yml"
+    )
+
+    def assert_never(arg: Never, /) -> Never:
+        value = repr(arg)
+        if len(value) > _ASSERT_NEVER_REPR_MAX_LENGTH:
+            value = value[:_ASSERT_NEVER_REPR_MAX_LENGTH] + "..."
+        msg = (
+            f"Expected code to be unreachable, but got: {value}.\n"
+            f"Please report an issue at {_BUG_URL}"
+        )
+        raise AssertionError(msg)
+
+
+__all__ = ["TypeVar", "assert_never", "deprecated"]