from typing import Any from typing import cast from typing import Dict from typing import Generic from typing import TypeVar from typing import Union __all__ = ["Stash", "StashKey"] T = TypeVar("T") D = TypeVar("D") class StashKey(Generic[T]): """``StashKey`` is an object used as a key to a :class:`Stash`. A ``StashKey`` is associated with the type ``T`` of the value of the key. A ``StashKey`` is unique and cannot conflict with another key. """ __slots__ = () class Stash: r"""``Stash`` is a type-safe heterogeneous mutable mapping that allows keys and value types to be defined separately from where it (the ``Stash``) is created. Usually you will be given an object which has a ``Stash``, for example :class:`~pytest.Config` or a :class:`~_pytest.nodes.Node`: .. code-block:: python stash: Stash = some_object.stash If a module or plugin wants to store data in this ``Stash``, it creates :class:`StashKey`\s for its keys (at the module level): .. code-block:: python # At the top-level of the module some_str_key = StashKey[str]() some_bool_key = StashKey[bool]() To store information: .. code-block:: python # Value type must match the key. stash[some_str_key] = "value" stash[some_bool_key] = True To retrieve the information: .. code-block:: python # The static type of some_str is str. some_str = stash[some_str_key] # The static type of some_bool is bool. some_bool = stash[some_bool_key] """ __slots__ = ("_storage",) def __init__(self) -> None: self._storage: Dict[StashKey[Any], object] = {} def __setitem__(self, key: StashKey[T], value: T) -> None: """Set a value for key.""" self._storage[key] = value def __getitem__(self, key: StashKey[T]) -> T: """Get the value for key. Raises ``KeyError`` if the key wasn't set before. """ return cast(T, self._storage[key]) def get(self, key: StashKey[T], default: D) -> Union[T, D]: """Get the value for key, or return default if the key wasn't set before.""" try: return self[key] except KeyError: return default def setdefault(self, key: StashKey[T], default: T) -> T: """Return the value of key if already set, otherwise set the value of key to default and return default.""" try: return self[key] except KeyError: self[key] = default return default def __delitem__(self, key: StashKey[T]) -> None: """Delete the value for key. Raises ``KeyError`` if the key wasn't set before. """ del self._storage[key] def __contains__(self, key: StashKey[T]) -> bool: """Return whether key was set.""" return key in self._storage def __len__(self) -> int: """Return how many items exist in the stash.""" return len(self._storage)