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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)
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