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+# inspection.py
+# Copyright (C) 2005-2024 the SQLAlchemy authors and contributors
+# <see AUTHORS file>
+#
+# This module is part of SQLAlchemy and is released under
+# the MIT License: https://www.opensource.org/licenses/mit-license.php
+
+"""The inspection module provides the :func:`_sa.inspect` function,
+which delivers runtime information about a wide variety
+of SQLAlchemy objects, both within the Core as well as the
+ORM.
+
+The :func:`_sa.inspect` function is the entry point to SQLAlchemy's
+public API for viewing the configuration and construction
+of in-memory objects. Depending on the type of object
+passed to :func:`_sa.inspect`, the return value will either be
+a related object which provides a known interface, or in many
+cases it will return the object itself.
+
+The rationale for :func:`_sa.inspect` is twofold. One is that
+it replaces the need to be aware of a large variety of "information
+getting" functions in SQLAlchemy, such as
+:meth:`_reflection.Inspector.from_engine` (deprecated in 1.4),
+:func:`.orm.attributes.instance_state`, :func:`_orm.class_mapper`,
+and others. The other is that the return value of :func:`_sa.inspect`
+is guaranteed to obey a documented API, thus allowing third party
+tools which build on top of SQLAlchemy configurations to be constructed
+in a forwards-compatible way.
+
+"""
+from __future__ import annotations
+
+from typing import Any
+from typing import Callable
+from typing import Dict
+from typing import Generic
+from typing import Optional
+from typing import overload
+from typing import Type
+from typing import TypeVar
+from typing import Union
+
+from . import exc
+from .util.typing import Literal
+from .util.typing import Protocol
+
+_T = TypeVar("_T", bound=Any)
+_TCov = TypeVar("_TCov", bound=Any, covariant=True)
+_F = TypeVar("_F", bound=Callable[..., Any])
+
+_IN = TypeVar("_IN", bound=Any)
+
+_registrars: Dict[type, Union[Literal[True], Callable[[Any], Any]]] = {}
+
+
+class Inspectable(Generic[_T]):
+ """define a class as inspectable.
+
+ This allows typing to set up a linkage between an object that
+ can be inspected and the type of inspection it returns.
+
+ Unfortunately we cannot at the moment get all classes that are
+ returned by inspection to suit this interface as we get into
+ MRO issues.
+
+ """
+
+ __slots__ = ()
+
+
+class _InspectableTypeProtocol(Protocol[_TCov]):
+ """a protocol defining a method that's used when a type (ie the class
+ itself) is passed to inspect().
+
+ """
+
+ def _sa_inspect_type(self) -> _TCov: ...
+
+
+class _InspectableProtocol(Protocol[_TCov]):
+ """a protocol defining a method that's used when an instance is
+ passed to inspect().
+
+ """
+
+ def _sa_inspect_instance(self) -> _TCov: ...
+
+
+@overload
+def inspect(
+ subject: Type[_InspectableTypeProtocol[_IN]], raiseerr: bool = True
+) -> _IN: ...
+
+
+@overload
+def inspect(
+ subject: _InspectableProtocol[_IN], raiseerr: bool = True
+) -> _IN: ...
+
+
+@overload
+def inspect(subject: Inspectable[_IN], raiseerr: bool = True) -> _IN: ...
+
+
+@overload
+def inspect(subject: Any, raiseerr: Literal[False] = ...) -> Optional[Any]: ...
+
+
+@overload
+def inspect(subject: Any, raiseerr: bool = True) -> Any: ...
+
+
+def inspect(subject: Any, raiseerr: bool = True) -> Any:
+ """Produce an inspection object for the given target.
+
+ The returned value in some cases may be the
+ same object as the one given, such as if a
+ :class:`_orm.Mapper` object is passed. In other
+ cases, it will be an instance of the registered
+ inspection type for the given object, such as
+ if an :class:`_engine.Engine` is passed, an
+ :class:`_reflection.Inspector` object is returned.
+
+ :param subject: the subject to be inspected.
+ :param raiseerr: When ``True``, if the given subject
+ does not
+ correspond to a known SQLAlchemy inspected type,
+ :class:`sqlalchemy.exc.NoInspectionAvailable`
+ is raised. If ``False``, ``None`` is returned.
+
+ """
+ type_ = type(subject)
+ for cls in type_.__mro__:
+ if cls in _registrars:
+ reg = _registrars.get(cls, None)
+ if reg is None:
+ continue
+ elif reg is True:
+ return subject
+ ret = reg(subject)
+ if ret is not None:
+ return ret
+ else:
+ reg = ret = None
+
+ if raiseerr and (reg is None or ret is None):
+ raise exc.NoInspectionAvailable(
+ "No inspection system is "
+ "available for object of type %s" % type_
+ )
+ return ret
+
+
+def _inspects(
+ *types: Type[Any],
+) -> Callable[[_F], _F]:
+ def decorate(fn_or_cls: _F) -> _F:
+ for type_ in types:
+ if type_ in _registrars:
+ raise AssertionError("Type %s is already registered" % type_)
+ _registrars[type_] = fn_or_cls
+ return fn_or_cls
+
+ return decorate
+
+
+_TT = TypeVar("_TT", bound="Type[Any]")
+
+
+def _self_inspects(cls: _TT) -> _TT:
+ if cls in _registrars:
+ raise AssertionError("Type %s is already registered" % cls)
+ _registrars[cls] = True
+ return cls