python lsp

server/libs/cattrs/fns.py

@@ -0,0 +1,22 @@
+"""Useful internal functions."""
+
+from typing import Any, Callable, NoReturn, TypeVar
+
+from ._compat import TypeAlias
+from .errors import StructureHandlerNotFoundError
+
+T = TypeVar("T")
+
+Predicate: TypeAlias = Callable[[Any], bool]
+"""A predicate function determines if a type can be handled."""
+
+
+def identity(obj: T) -> T:
+    """The identity function."""
+    return obj
+
+
+def raise_error(_, cl: Any) -> NoReturn:
+    """At the bottom of the condition stack, we explode if we can't handle it."""
+    msg = f"Unsupported type: {cl!r}. Register a structure hook for it."
+    raise StructureHandlerNotFoundError(msg, type_=cl)