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from __future__ import annotations
import abc
import typing as t
from contextvars import ContextVar
from ansible.module_utils._internal._datatag import AnsibleTagHelper
class NotifiableAccessContextBase(metaclass=abc.ABCMeta):
"""Base class for a context manager that, when active, receives notification of managed access for types/tags in which it has registered an interest."""
_type_interest: t.FrozenSet[type] = frozenset()
"""Set of types (including tag types) for which this context will be notified upon access."""
_mask: t.ClassVar[bool] = False
"""When true, only the innermost (most recently created) context of this type will be notified."""
def __enter__(self):
# noinspection PyProtectedMember
AnsibleAccessContext.current()._register_interest(self)
return self
def __exit__(self, exc_type, exc_val, exc_tb) -> None:
# noinspection PyProtectedMember
AnsibleAccessContext.current()._unregister_interest(self)
return None
@abc.abstractmethod
def _notify(self, o: t.Any) -> t.Any:
"""Derived classes implement custom notification behavior when a registered type or tag is accessed."""
class AnsibleAccessContext:
"""
Broker object for managed access registration and notification.
Each thread or other logical callstack has a dedicated `AnsibleAccessContext` object with which `NotifiableAccessContext` objects can register interest.
When a managed access occurs on an object, each active `NotifiableAccessContext` within the current callstack that has registered interest in that
object's type or a tag present on it will be notified.
"""
_contextvar: t.ClassVar[ContextVar[AnsibleAccessContext]] = ContextVar('AnsibleAccessContext')
@staticmethod
def current() -> AnsibleAccessContext:
"""Creates or retrieves an `AnsibleAccessContext` for the current logical callstack."""
try:
ctx: AnsibleAccessContext = AnsibleAccessContext._contextvar.get()
except LookupError:
# didn't exist; create it
ctx = AnsibleAccessContext()
AnsibleAccessContext._contextvar.set(ctx) # we ignore the token, since this should live for the life of the thread/async ctx
return ctx
def __init__(self) -> None:
self._notify_contexts: list[NotifiableAccessContextBase] = []
def _register_interest(self, context: NotifiableAccessContextBase) -> None:
self._notify_contexts.append(context)
def _unregister_interest(self, context: NotifiableAccessContextBase) -> None:
ctx = self._notify_contexts.pop()
if ctx is not context:
raise RuntimeError(f'Out-of-order context deactivation detected. Found {ctx} instead of {context}.')
def access(self, value: t.Any) -> None:
"""Notify all contexts which have registered interest in the given value that it is being accessed."""
if not self._notify_contexts:
return
value_types = AnsibleTagHelper.tag_types(value) | frozenset((type(value),))
masked: set[type] = set()
for ctx in reversed(self._notify_contexts):
if ctx._mask:
if (ctx_type := type(ctx)) in masked:
continue
masked.add(ctx_type)
# noinspection PyProtectedMember
if ctx._type_interest.intersection(value_types):
ctx._notify(value)
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