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+# orm/collections.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
+# mypy: allow-untyped-defs, allow-untyped-calls
+
+"""Support for collections of mapped entities.
+
+The collections package supplies the machinery used to inform the ORM of
+collection membership changes.  An instrumentation via decoration approach is
+used, allowing arbitrary types (including built-ins) to be used as entity
+collections without requiring inheritance from a base class.
+
+Instrumentation decoration relays membership change events to the
+:class:`.CollectionAttributeImpl` that is currently managing the collection.
+The decorators observe function call arguments and return values, tracking
+entities entering or leaving the collection.  Two decorator approaches are
+provided.  One is a bundle of generic decorators that map function arguments
+and return values to events::
+
+  from sqlalchemy.orm.collections import collection
+  class MyClass:
+      # ...
+
+      @collection.adds(1)
+      def store(self, item):
+          self.data.append(item)
+
+      @collection.removes_return()
+      def pop(self):
+          return self.data.pop()
+
+
+The second approach is a bundle of targeted decorators that wrap appropriate
+append and remove notifiers around the mutation methods present in the
+standard Python ``list``, ``set`` and ``dict`` interfaces.  These could be
+specified in terms of generic decorator recipes, but are instead hand-tooled
+for increased efficiency.  The targeted decorators occasionally implement
+adapter-like behavior, such as mapping bulk-set methods (``extend``,
+``update``, ``__setslice__``, etc.) into the series of atomic mutation events
+that the ORM requires.
+
+The targeted decorators are used internally for automatic instrumentation of
+entity collection classes.  Every collection class goes through a
+transformation process roughly like so:
+
+1. If the class is a built-in, substitute a trivial sub-class
+2. Is this class already instrumented?
+3. Add in generic decorators
+4. Sniff out the collection interface through duck-typing
+5. Add targeted decoration to any undecorated interface method
+
+This process modifies the class at runtime, decorating methods and adding some
+bookkeeping properties.  This isn't possible (or desirable) for built-in
+classes like ``list``, so trivial sub-classes are substituted to hold
+decoration::
+
+  class InstrumentedList(list):
+      pass
+
+Collection classes can be specified in ``relationship(collection_class=)`` as
+types or a function that returns an instance.  Collection classes are
+inspected and instrumented during the mapper compilation phase.  The
+collection_class callable will be executed once to produce a specimen
+instance, and the type of that specimen will be instrumented.  Functions that
+return built-in types like ``lists`` will be adapted to produce instrumented
+instances.
+
+When extending a known type like ``list``, additional decorations are not
+generally not needed.  Odds are, the extension method will delegate to a
+method that's already instrumented.  For example::
+
+  class QueueIsh(list):
+     def push(self, item):
+         self.append(item)
+     def shift(self):
+         return self.pop(0)
+
+There's no need to decorate these methods.  ``append`` and ``pop`` are already
+instrumented as part of the ``list`` interface.  Decorating them would fire
+duplicate events, which should be avoided.
+
+The targeted decoration tries not to rely on other methods in the underlying
+collection class, but some are unavoidable.  Many depend on 'read' methods
+being present to properly instrument a 'write', for example, ``__setitem__``
+needs ``__getitem__``.  "Bulk" methods like ``update`` and ``extend`` may also
+reimplemented in terms of atomic appends and removes, so the ``extend``
+decoration will actually perform many ``append`` operations and not call the
+underlying method at all.
+
+Tight control over bulk operation and the firing of events is also possible by
+implementing the instrumentation internally in your methods.  The basic
+instrumentation package works under the general assumption that collection
+mutation will not raise unusual exceptions.  If you want to closely
+orchestrate append and remove events with exception management, internal
+instrumentation may be the answer.  Within your method,
+``collection_adapter(self)`` will retrieve an object that you can use for
+explicit control over triggering append and remove events.
+
+The owning object and :class:`.CollectionAttributeImpl` are also reachable
+through the adapter, allowing for some very sophisticated behavior.
+
+"""
+from __future__ import annotations
+
+import operator
+import threading
+import typing
+from typing import Any
+from typing import Callable
+from typing import cast
+from typing import Collection
+from typing import Dict
+from typing import Iterable
+from typing import List
+from typing import NoReturn
+from typing import Optional
+from typing import Set
+from typing import Tuple
+from typing import Type
+from typing import TYPE_CHECKING
+from typing import TypeVar
+from typing import Union
+import weakref
+
+from .base import NO_KEY
+from .. import exc as sa_exc
+from .. import util
+from ..sql.base import NO_ARG
+from ..util.compat import inspect_getfullargspec
+from ..util.typing import Protocol
+
+if typing.TYPE_CHECKING:
+    from .attributes import AttributeEventToken
+    from .attributes import CollectionAttributeImpl
+    from .mapped_collection import attribute_keyed_dict
+    from .mapped_collection import column_keyed_dict
+    from .mapped_collection import keyfunc_mapping
+    from .mapped_collection import KeyFuncDict  # noqa: F401
+    from .state import InstanceState
+
+
+__all__ = [
+    "collection",
+    "collection_adapter",
+    "keyfunc_mapping",
+    "column_keyed_dict",
+    "attribute_keyed_dict",
+    "column_keyed_dict",
+    "attribute_keyed_dict",
+    "MappedCollection",
+    "KeyFuncDict",
+]
+
+__instrumentation_mutex = threading.Lock()
+
+
+_CollectionFactoryType = Callable[[], "_AdaptedCollectionProtocol"]
+
+_T = TypeVar("_T", bound=Any)
+_KT = TypeVar("_KT", bound=Any)
+_VT = TypeVar("_VT", bound=Any)
+_COL = TypeVar("_COL", bound="Collection[Any]")
+_FN = TypeVar("_FN", bound="Callable[..., Any]")
+
+
+class _CollectionConverterProtocol(Protocol):
+    def __call__(self, collection: _COL) -> _COL: ...
+
+
+class _AdaptedCollectionProtocol(Protocol):
+    _sa_adapter: CollectionAdapter
+    _sa_appender: Callable[..., Any]
+    _sa_remover: Callable[..., Any]
+    _sa_iterator: Callable[..., Iterable[Any]]
+    _sa_converter: _CollectionConverterProtocol
+
+
+class collection:
+    """Decorators for entity collection classes.
+
+    The decorators fall into two groups: annotations and interception recipes.
+
+    The annotating decorators (appender, remover, iterator, converter,
+    internally_instrumented) indicate the method's purpose and take no
+    arguments.  They are not written with parens::
+
+        @collection.appender
+        def append(self, append): ...
+
+    The recipe decorators all require parens, even those that take no
+    arguments::
+
+        @collection.adds('entity')
+        def insert(self, position, entity): ...
+
+        @collection.removes_return()
+        def popitem(self): ...
+
+    """
+
+    # Bundled as a class solely for ease of use: packaging, doc strings,
+    # importability.
+
+    @staticmethod
+    def appender(fn):
+        """Tag the method as the collection appender.
+
+        The appender method is called with one positional argument: the value
+        to append. The method will be automatically decorated with 'adds(1)'
+        if not already decorated::
+
+            @collection.appender
+            def add(self, append): ...
+
+            # or, equivalently
+            @collection.appender
+            @collection.adds(1)
+            def add(self, append): ...
+
+            # for mapping type, an 'append' may kick out a previous value
+            # that occupies that slot.  consider d['a'] = 'foo'- any previous
+            # value in d['a'] is discarded.
+            @collection.appender
+            @collection.replaces(1)
+            def add(self, entity):
+                key = some_key_func(entity)
+                previous = None
+                if key in self:
+                    previous = self[key]
+                self[key] = entity
+                return previous
+
+        If the value to append is not allowed in the collection, you may
+        raise an exception.  Something to remember is that the appender
+        will be called for each object mapped by a database query.  If the
+        database contains rows that violate your collection semantics, you
+        will need to get creative to fix the problem, as access via the
+        collection will not work.
+
+        If the appender method is internally instrumented, you must also
+        receive the keyword argument '_sa_initiator' and ensure its
+        promulgation to collection events.
+
+        """
+        fn._sa_instrument_role = "appender"
+        return fn
+
+    @staticmethod
+    def remover(fn):
+        """Tag the method as the collection remover.
+
+        The remover method is called with one positional argument: the value
+        to remove. The method will be automatically decorated with
+        :meth:`removes_return` if not already decorated::
+
+            @collection.remover
+            def zap(self, entity): ...
+
+            # or, equivalently
+            @collection.remover
+            @collection.removes_return()
+            def zap(self, ): ...
+
+        If the value to remove is not present in the collection, you may
+        raise an exception or return None to ignore the error.
+
+        If the remove method is internally instrumented, you must also
+        receive the keyword argument '_sa_initiator' and ensure its
+        promulgation to collection events.
+
+        """
+        fn._sa_instrument_role = "remover"
+        return fn
+
+    @staticmethod
+    def iterator(fn):
+        """Tag the method as the collection remover.
+
+        The iterator method is called with no arguments.  It is expected to
+        return an iterator over all collection members::
+
+            @collection.iterator
+            def __iter__(self): ...
+
+        """
+        fn._sa_instrument_role = "iterator"
+        return fn
+
+    @staticmethod
+    def internally_instrumented(fn):
+        """Tag the method as instrumented.
+
+        This tag will prevent any decoration from being applied to the
+        method. Use this if you are orchestrating your own calls to
+        :func:`.collection_adapter` in one of the basic SQLAlchemy
+        interface methods, or to prevent an automatic ABC method
+        decoration from wrapping your implementation::
+
+            # normally an 'extend' method on a list-like class would be
+            # automatically intercepted and re-implemented in terms of
+            # SQLAlchemy events and append().  your implementation will
+            # never be called, unless:
+            @collection.internally_instrumented
+            def extend(self, items): ...
+
+        """
+        fn._sa_instrumented = True
+        return fn
+
+    @staticmethod
+    @util.deprecated(
+        "1.3",
+        "The :meth:`.collection.converter` handler is deprecated and will "
+        "be removed in a future release.  Please refer to the "
+        ":class:`.AttributeEvents.bulk_replace` listener interface in "
+        "conjunction with the :func:`.event.listen` function.",
+    )
+    def converter(fn):
+        """Tag the method as the collection converter.
+
+        This optional method will be called when a collection is being
+        replaced entirely, as in::
+
+            myobj.acollection = [newvalue1, newvalue2]
+
+        The converter method will receive the object being assigned and should
+        return an iterable of values suitable for use by the ``appender``
+        method.  A converter must not assign values or mutate the collection,
+        its sole job is to adapt the value the user provides into an iterable
+        of values for the ORM's use.
+
+        The default converter implementation will use duck-typing to do the
+        conversion.  A dict-like collection will be convert into an iterable
+        of dictionary values, and other types will simply be iterated::
+
+            @collection.converter
+            def convert(self, other): ...
+
+        If the duck-typing of the object does not match the type of this
+        collection, a TypeError is raised.
+
+        Supply an implementation of this method if you want to expand the
+        range of possible types that can be assigned in bulk or perform
+        validation on the values about to be assigned.
+
+        """
+        fn._sa_instrument_role = "converter"
+        return fn
+
+    @staticmethod
+    def adds(arg):
+        """Mark the method as adding an entity to the collection.
+
+        Adds "add to collection" handling to the method.  The decorator
+        argument indicates which method argument holds the SQLAlchemy-relevant
+        value.  Arguments can be specified positionally (i.e. integer) or by
+        name::
+
+            @collection.adds(1)
+            def push(self, item): ...
+
+            @collection.adds('entity')
+            def do_stuff(self, thing, entity=None): ...
+
+        """
+
+        def decorator(fn):
+            fn._sa_instrument_before = ("fire_append_event", arg)
+            return fn
+
+        return decorator
+
+    @staticmethod
+    def replaces(arg):
+        """Mark the method as replacing an entity in the collection.
+
+        Adds "add to collection" and "remove from collection" handling to
+        the method.  The decorator argument indicates which method argument
+        holds the SQLAlchemy-relevant value to be added, and return value, if
+        any will be considered the value to remove.
+
+        Arguments can be specified positionally (i.e. integer) or by name::
+
+            @collection.replaces(2)
+            def __setitem__(self, index, item): ...
+
+        """
+
+        def decorator(fn):
+            fn._sa_instrument_before = ("fire_append_event", arg)
+            fn._sa_instrument_after = "fire_remove_event"
+            return fn
+
+        return decorator
+
+    @staticmethod
+    def removes(arg):
+        """Mark the method as removing an entity in the collection.
+
+        Adds "remove from collection" handling to the method.  The decorator
+        argument indicates which method argument holds the SQLAlchemy-relevant
+        value to be removed. Arguments can be specified positionally (i.e.
+        integer) or by name::
+
+            @collection.removes(1)
+            def zap(self, item): ...
+
+        For methods where the value to remove is not known at call-time, use
+        collection.removes_return.
+
+        """
+
+        def decorator(fn):
+            fn._sa_instrument_before = ("fire_remove_event", arg)
+            return fn
+
+        return decorator
+
+    @staticmethod
+    def removes_return():
+        """Mark the method as removing an entity in the collection.
+
+        Adds "remove from collection" handling to the method.  The return
+        value of the method, if any, is considered the value to remove.  The
+        method arguments are not inspected::
+
+            @collection.removes_return()
+            def pop(self): ...
+
+        For methods where the value to remove is known at call-time, use
+        collection.remove.
+
+        """
+
+        def decorator(fn):
+            fn._sa_instrument_after = "fire_remove_event"
+            return fn
+
+        return decorator
+
+
+if TYPE_CHECKING:
+
+    def collection_adapter(collection: Collection[Any]) -> CollectionAdapter:
+        """Fetch the :class:`.CollectionAdapter` for a collection."""
+
+else:
+    collection_adapter = operator.attrgetter("_sa_adapter")
+
+
+class CollectionAdapter:
+    """Bridges between the ORM and arbitrary Python collections.
+
+    Proxies base-level collection operations (append, remove, iterate)
+    to the underlying Python collection, and emits add/remove events for
+    entities entering or leaving the collection.
+
+    The ORM uses :class:`.CollectionAdapter` exclusively for interaction with
+    entity collections.
+
+
+    """
+
+    __slots__ = (
+        "attr",
+        "_key",
+        "_data",
+        "owner_state",
+        "_converter",
+        "invalidated",
+        "empty",
+    )
+
+    attr: CollectionAttributeImpl
+    _key: str
+
+    # this is actually a weakref; see note in constructor
+    _data: Callable[..., _AdaptedCollectionProtocol]
+
+    owner_state: InstanceState[Any]
+    _converter: _CollectionConverterProtocol
+    invalidated: bool
+    empty: bool
+
+    def __init__(
+        self,
+        attr: CollectionAttributeImpl,
+        owner_state: InstanceState[Any],
+        data: _AdaptedCollectionProtocol,
+    ):
+        self.attr = attr
+        self._key = attr.key
+
+        # this weakref stays referenced throughout the lifespan of
+        # CollectionAdapter.  so while the weakref can return None, this
+        # is realistically only during garbage collection of this object, so
+        # we type this as a callable that returns _AdaptedCollectionProtocol
+        # in all cases.
+        self._data = weakref.ref(data)  # type: ignore
+
+        self.owner_state = owner_state
+        data._sa_adapter = self
+        self._converter = data._sa_converter
+        self.invalidated = False
+        self.empty = False
+
+    def _warn_invalidated(self) -> None:
+        util.warn("This collection has been invalidated.")
+
+    @property
+    def data(self) -> _AdaptedCollectionProtocol:
+        "The entity collection being adapted."
+        return self._data()
+
+    @property
+    def _referenced_by_owner(self) -> bool:
+        """return True if the owner state still refers to this collection.
+
+        This will return False within a bulk replace operation,
+        where this collection is the one being replaced.
+
+        """
+        return self.owner_state.dict[self._key] is self._data()
+
+    def bulk_appender(self):
+        return self._data()._sa_appender
+
+    def append_with_event(
+        self, item: Any, initiator: Optional[AttributeEventToken] = None
+    ) -> None:
+        """Add an entity to the collection, firing mutation events."""
+
+        self._data()._sa_appender(item, _sa_initiator=initiator)
+
+    def _set_empty(self, user_data):
+        assert (
+            not self.empty
+        ), "This collection adapter is already in the 'empty' state"
+        self.empty = True
+        self.owner_state._empty_collections[self._key] = user_data
+
+    def _reset_empty(self) -> None:
+        assert (
+            self.empty
+        ), "This collection adapter is not in the 'empty' state"
+        self.empty = False
+        self.owner_state.dict[self._key] = (
+            self.owner_state._empty_collections.pop(self._key)
+        )
+
+    def _refuse_empty(self) -> NoReturn:
+        raise sa_exc.InvalidRequestError(
+            "This is a special 'empty' collection which cannot accommodate "
+            "internal mutation operations"
+        )
+
+    def append_without_event(self, item: Any) -> None:
+        """Add or restore an entity to the collection, firing no events."""
+
+        if self.empty:
+            self._refuse_empty()
+        self._data()._sa_appender(item, _sa_initiator=False)
+
+    def append_multiple_without_event(self, items: Iterable[Any]) -> None:
+        """Add or restore an entity to the collection, firing no events."""
+        if self.empty:
+            self._refuse_empty()
+        appender = self._data()._sa_appender
+        for item in items:
+            appender(item, _sa_initiator=False)
+
+    def bulk_remover(self):
+        return self._data()._sa_remover
+
+    def remove_with_event(
+        self, item: Any, initiator: Optional[AttributeEventToken] = None
+    ) -> None:
+        """Remove an entity from the collection, firing mutation events."""
+        self._data()._sa_remover(item, _sa_initiator=initiator)
+
+    def remove_without_event(self, item: Any) -> None:
+        """Remove an entity from the collection, firing no events."""
+        if self.empty:
+            self._refuse_empty()
+        self._data()._sa_remover(item, _sa_initiator=False)
+
+    def clear_with_event(
+        self, initiator: Optional[AttributeEventToken] = None
+    ) -> None:
+        """Empty the collection, firing a mutation event for each entity."""
+
+        if self.empty:
+            self._refuse_empty()
+        remover = self._data()._sa_remover
+        for item in list(self):
+            remover(item, _sa_initiator=initiator)
+
+    def clear_without_event(self) -> None:
+        """Empty the collection, firing no events."""
+
+        if self.empty:
+            self._refuse_empty()
+        remover = self._data()._sa_remover
+        for item in list(self):
+            remover(item, _sa_initiator=False)
+
+    def __iter__(self):
+        """Iterate over entities in the collection."""
+
+        return iter(self._data()._sa_iterator())
+
+    def __len__(self):
+        """Count entities in the collection."""
+        return len(list(self._data()._sa_iterator()))
+
+    def __bool__(self):
+        return True
+
+    def _fire_append_wo_mutation_event_bulk(
+        self, items, initiator=None, key=NO_KEY
+    ):
+        if not items:
+            return
+
+        if initiator is not False:
+            if self.invalidated:
+                self._warn_invalidated()
+
+            if self.empty:
+                self._reset_empty()
+
+            for item in items:
+                self.attr.fire_append_wo_mutation_event(
+                    self.owner_state,
+                    self.owner_state.dict,
+                    item,
+                    initiator,
+                    key,
+                )
+
+    def fire_append_wo_mutation_event(self, item, initiator=None, key=NO_KEY):
+        """Notify that a entity is entering the collection but is already
+        present.
+
+
+        Initiator is a token owned by the InstrumentedAttribute that
+        initiated the membership mutation, and should be left as None
+        unless you are passing along an initiator value from a chained
+        operation.
+
+        .. versionadded:: 1.4.15
+
+        """
+        if initiator is not False:
+            if self.invalidated:
+                self._warn_invalidated()
+
+            if self.empty:
+                self._reset_empty()
+
+            return self.attr.fire_append_wo_mutation_event(
+                self.owner_state, self.owner_state.dict, item, initiator, key
+            )
+        else:
+            return item
+
+    def fire_append_event(self, item, initiator=None, key=NO_KEY):
+        """Notify that a entity has entered the collection.
+
+        Initiator is a token owned by the InstrumentedAttribute that
+        initiated the membership mutation, and should be left as None
+        unless you are passing along an initiator value from a chained
+        operation.
+
+        """
+        if initiator is not False:
+            if self.invalidated:
+                self._warn_invalidated()
+
+            if self.empty:
+                self._reset_empty()
+
+            return self.attr.fire_append_event(
+                self.owner_state, self.owner_state.dict, item, initiator, key
+            )
+        else:
+            return item
+
+    def _fire_remove_event_bulk(self, items, initiator=None, key=NO_KEY):
+        if not items:
+            return
+
+        if initiator is not False:
+            if self.invalidated:
+                self._warn_invalidated()
+
+            if self.empty:
+                self._reset_empty()
+
+            for item in items:
+                self.attr.fire_remove_event(
+                    self.owner_state,
+                    self.owner_state.dict,
+                    item,
+                    initiator,
+                    key,
+                )
+
+    def fire_remove_event(self, item, initiator=None, key=NO_KEY):
+        """Notify that a entity has been removed from the collection.
+
+        Initiator is the InstrumentedAttribute that initiated the membership
+        mutation, and should be left as None unless you are passing along
+        an initiator value from a chained operation.
+
+        """
+        if initiator is not False:
+            if self.invalidated:
+                self._warn_invalidated()
+
+            if self.empty:
+                self._reset_empty()
+
+            self.attr.fire_remove_event(
+                self.owner_state, self.owner_state.dict, item, initiator, key
+            )
+
+    def fire_pre_remove_event(self, initiator=None, key=NO_KEY):
+        """Notify that an entity is about to be removed from the collection.
+
+        Only called if the entity cannot be removed after calling
+        fire_remove_event().
+
+        """
+        if self.invalidated:
+            self._warn_invalidated()
+        self.attr.fire_pre_remove_event(
+            self.owner_state,
+            self.owner_state.dict,
+            initiator=initiator,
+            key=key,
+        )
+
+    def __getstate__(self):
+        return {
+            "key": self._key,
+            "owner_state": self.owner_state,
+            "owner_cls": self.owner_state.class_,
+            "data": self.data,
+            "invalidated": self.invalidated,
+            "empty": self.empty,
+        }
+
+    def __setstate__(self, d):
+        self._key = d["key"]
+        self.owner_state = d["owner_state"]
+
+        # see note in constructor regarding this type: ignore
+        self._data = weakref.ref(d["data"])  # type: ignore
+
+        self._converter = d["data"]._sa_converter
+        d["data"]._sa_adapter = self
+        self.invalidated = d["invalidated"]
+        self.attr = getattr(d["owner_cls"], self._key).impl
+        self.empty = d.get("empty", False)
+
+
+def bulk_replace(values, existing_adapter, new_adapter, initiator=None):
+    """Load a new collection, firing events based on prior like membership.
+
+    Appends instances in ``values`` onto the ``new_adapter``. Events will be
+    fired for any instance not present in the ``existing_adapter``.  Any
+    instances in ``existing_adapter`` not present in ``values`` will have
+    remove events fired upon them.
+
+    :param values: An iterable of collection member instances
+
+    :param existing_adapter: A :class:`.CollectionAdapter` of
+     instances to be replaced
+
+    :param new_adapter: An empty :class:`.CollectionAdapter`
+     to load with ``values``
+
+
+    """
+
+    assert isinstance(values, list)
+
+    idset = util.IdentitySet
+    existing_idset = idset(existing_adapter or ())
+    constants = existing_idset.intersection(values or ())
+    additions = idset(values or ()).difference(constants)
+    removals = existing_idset.difference(constants)
+
+    appender = new_adapter.bulk_appender()
+
+    for member in values or ():
+        if member in additions:
+            appender(member, _sa_initiator=initiator)
+        elif member in constants:
+            appender(member, _sa_initiator=False)
+
+    if existing_adapter:
+        existing_adapter._fire_append_wo_mutation_event_bulk(
+            constants, initiator=initiator
+        )
+        existing_adapter._fire_remove_event_bulk(removals, initiator=initiator)
+
+
+def prepare_instrumentation(
+    factory: Union[Type[Collection[Any]], _CollectionFactoryType],
+) -> _CollectionFactoryType:
+    """Prepare a callable for future use as a collection class factory.
+
+    Given a collection class factory (either a type or no-arg callable),
+    return another factory that will produce compatible instances when
+    called.
+
+    This function is responsible for converting collection_class=list
+    into the run-time behavior of collection_class=InstrumentedList.
+
+    """
+
+    impl_factory: _CollectionFactoryType
+
+    # Convert a builtin to 'Instrumented*'
+    if factory in __canned_instrumentation:
+        impl_factory = __canned_instrumentation[factory]
+    else:
+        impl_factory = cast(_CollectionFactoryType, factory)
+
+    cls: Union[_CollectionFactoryType, Type[Collection[Any]]]
+
+    # Create a specimen
+    cls = type(impl_factory())
+
+    # Did factory callable return a builtin?
+    if cls in __canned_instrumentation:
+        # if so, just convert.
+        # in previous major releases, this codepath wasn't working and was
+        # not covered by tests.   prior to that it supplied a "wrapper"
+        # function that would return the class, though the rationale for this
+        # case is not known
+        impl_factory = __canned_instrumentation[cls]
+        cls = type(impl_factory())
+
+    # Instrument the class if needed.
+    if __instrumentation_mutex.acquire():
+        try:
+            if getattr(cls, "_sa_instrumented", None) != id(cls):
+                _instrument_class(cls)
+        finally:
+            __instrumentation_mutex.release()
+
+    return impl_factory
+
+
+def _instrument_class(cls):
+    """Modify methods in a class and install instrumentation."""
+
+    # In the normal call flow, a request for any of the 3 basic collection
+    # types is transformed into one of our trivial subclasses
+    # (e.g. InstrumentedList).  Catch anything else that sneaks in here...
+    if cls.__module__ == "__builtin__":
+        raise sa_exc.ArgumentError(
+            "Can not instrument a built-in type. Use a "
+            "subclass, even a trivial one."
+        )
+
+    roles, methods = _locate_roles_and_methods(cls)
+
+    _setup_canned_roles(cls, roles, methods)
+
+    _assert_required_roles(cls, roles, methods)
+
+    _set_collection_attributes(cls, roles, methods)
+
+
+def _locate_roles_and_methods(cls):
+    """search for _sa_instrument_role-decorated methods in
+    method resolution order, assign to roles.
+
+    """
+
+    roles: Dict[str, str] = {}
+    methods: Dict[str, Tuple[Optional[str], Optional[int], Optional[str]]] = {}
+
+    for supercls in cls.__mro__:
+        for name, method in vars(supercls).items():
+            if not callable(method):
+                continue
+
+            # note role declarations
+            if hasattr(method, "_sa_instrument_role"):
+                role = method._sa_instrument_role
+                assert role in (
+                    "appender",
+                    "remover",
+                    "iterator",
+                    "converter",
+                )
+                roles.setdefault(role, name)
+
+            # transfer instrumentation requests from decorated function
+            # to the combined queue
+            before: Optional[Tuple[str, int]] = None
+            after: Optional[str] = None
+
+            if hasattr(method, "_sa_instrument_before"):
+                op, argument = method._sa_instrument_before
+                assert op in ("fire_append_event", "fire_remove_event")
+                before = op, argument
+            if hasattr(method, "_sa_instrument_after"):
+                op = method._sa_instrument_after
+                assert op in ("fire_append_event", "fire_remove_event")
+                after = op
+            if before:
+                methods[name] = before + (after,)
+            elif after:
+                methods[name] = None, None, after
+    return roles, methods
+
+
+def _setup_canned_roles(cls, roles, methods):
+    """see if this class has "canned" roles based on a known
+    collection type (dict, set, list).  Apply those roles
+    as needed to the "roles" dictionary, and also
+    prepare "decorator" methods
+
+    """
+    collection_type = util.duck_type_collection(cls)
+    if collection_type in __interfaces:
+        assert collection_type is not None
+        canned_roles, decorators = __interfaces[collection_type]
+        for role, name in canned_roles.items():
+            roles.setdefault(role, name)
+
+        # apply ABC auto-decoration to methods that need it
+        for method, decorator in decorators.items():
+            fn = getattr(cls, method, None)
+            if (
+                fn
+                and method not in methods
+                and not hasattr(fn, "_sa_instrumented")
+            ):
+                setattr(cls, method, decorator(fn))
+
+
+def _assert_required_roles(cls, roles, methods):
+    """ensure all roles are present, and apply implicit instrumentation if
+    needed
+
+    """
+    if "appender" not in roles or not hasattr(cls, roles["appender"]):
+        raise sa_exc.ArgumentError(
+            "Type %s must elect an appender method to be "
+            "a collection class" % cls.__name__
+        )
+    elif roles["appender"] not in methods and not hasattr(
+        getattr(cls, roles["appender"]), "_sa_instrumented"
+    ):
+        methods[roles["appender"]] = ("fire_append_event", 1, None)
+
+    if "remover" not in roles or not hasattr(cls, roles["remover"]):
+        raise sa_exc.ArgumentError(
+            "Type %s must elect a remover method to be "
+            "a collection class" % cls.__name__
+        )
+    elif roles["remover"] not in methods and not hasattr(
+        getattr(cls, roles["remover"]), "_sa_instrumented"
+    ):
+        methods[roles["remover"]] = ("fire_remove_event", 1, None)
+
+    if "iterator" not in roles or not hasattr(cls, roles["iterator"]):
+        raise sa_exc.ArgumentError(
+            "Type %s must elect an iterator method to be "
+            "a collection class" % cls.__name__
+        )
+
+
+def _set_collection_attributes(cls, roles, methods):
+    """apply ad-hoc instrumentation from decorators, class-level defaults
+    and implicit role declarations
+
+    """
+    for method_name, (before, argument, after) in methods.items():
+        setattr(
+            cls,
+            method_name,
+            _instrument_membership_mutator(
+                getattr(cls, method_name), before, argument, after
+            ),
+        )
+    # intern the role map
+    for role, method_name in roles.items():
+        setattr(cls, "_sa_%s" % role, getattr(cls, method_name))
+
+    cls._sa_adapter = None
+
+    if not hasattr(cls, "_sa_converter"):
+        cls._sa_converter = None
+    cls._sa_instrumented = id(cls)
+
+
+def _instrument_membership_mutator(method, before, argument, after):
+    """Route method args and/or return value through the collection
+    adapter."""
+    # This isn't smart enough to handle @adds(1) for 'def fn(self, (a, b))'
+    if before:
+        fn_args = list(
+            util.flatten_iterator(inspect_getfullargspec(method)[0])
+        )
+        if isinstance(argument, int):
+            pos_arg = argument
+            named_arg = len(fn_args) > argument and fn_args[argument] or None
+        else:
+            if argument in fn_args:
+                pos_arg = fn_args.index(argument)
+            else:
+                pos_arg = None
+            named_arg = argument
+        del fn_args
+
+    def wrapper(*args, **kw):
+        if before:
+            if pos_arg is None:
+                if named_arg not in kw:
+                    raise sa_exc.ArgumentError(
+                        "Missing argument %s" % argument
+                    )
+                value = kw[named_arg]
+            else:
+                if len(args) > pos_arg:
+                    value = args[pos_arg]
+                elif named_arg in kw:
+                    value = kw[named_arg]
+                else:
+                    raise sa_exc.ArgumentError(
+                        "Missing argument %s" % argument
+                    )
+
+        initiator = kw.pop("_sa_initiator", None)
+        if initiator is False:
+            executor = None
+        else:
+            executor = args[0]._sa_adapter
+
+        if before and executor:
+            getattr(executor, before)(value, initiator)
+
+        if not after or not executor:
+            return method(*args, **kw)
+        else:
+            res = method(*args, **kw)
+            if res is not None:
+                getattr(executor, after)(res, initiator)
+            return res
+
+    wrapper._sa_instrumented = True  # type: ignore[attr-defined]
+    if hasattr(method, "_sa_instrument_role"):
+        wrapper._sa_instrument_role = method._sa_instrument_role  # type: ignore[attr-defined]  # noqa: E501
+    wrapper.__name__ = method.__name__
+    wrapper.__doc__ = method.__doc__
+    return wrapper
+
+
+def __set_wo_mutation(collection, item, _sa_initiator=None):
+    """Run set wo mutation events.
+
+    The collection is not mutated.
+
+    """
+    if _sa_initiator is not False:
+        executor = collection._sa_adapter
+        if executor:
+            executor.fire_append_wo_mutation_event(
+                item, _sa_initiator, key=None
+            )
+
+
+def __set(collection, item, _sa_initiator, key):
+    """Run set events.
+
+    This event always occurs before the collection is actually mutated.
+
+    """
+
+    if _sa_initiator is not False:
+        executor = collection._sa_adapter
+        if executor:
+            item = executor.fire_append_event(item, _sa_initiator, key=key)
+    return item
+
+
+def __del(collection, item, _sa_initiator, key):
+    """Run del events.
+
+    This event occurs before the collection is actually mutated, *except*
+    in the case of a pop operation, in which case it occurs afterwards.
+    For pop operations, the __before_pop hook is called before the
+    operation occurs.
+
+    """
+    if _sa_initiator is not False:
+        executor = collection._sa_adapter
+        if executor:
+            executor.fire_remove_event(item, _sa_initiator, key=key)
+
+
+def __before_pop(collection, _sa_initiator=None):
+    """An event which occurs on a before a pop() operation occurs."""
+    executor = collection._sa_adapter
+    if executor:
+        executor.fire_pre_remove_event(_sa_initiator)
+
+
+def _list_decorators() -> Dict[str, Callable[[_FN], _FN]]:
+    """Tailored instrumentation wrappers for any list-like class."""
+
+    def _tidy(fn):
+        fn._sa_instrumented = True
+        fn.__doc__ = getattr(list, fn.__name__).__doc__
+
+    def append(fn):
+        def append(self, item, _sa_initiator=None):
+            item = __set(self, item, _sa_initiator, NO_KEY)
+            fn(self, item)
+
+        _tidy(append)
+        return append
+
+    def remove(fn):
+        def remove(self, value, _sa_initiator=None):
+            __del(self, value, _sa_initiator, NO_KEY)
+            # testlib.pragma exempt:__eq__
+            fn(self, value)
+
+        _tidy(remove)
+        return remove
+
+    def insert(fn):
+        def insert(self, index, value):
+            value = __set(self, value, None, index)
+            fn(self, index, value)
+
+        _tidy(insert)
+        return insert
+
+    def __setitem__(fn):
+        def __setitem__(self, index, value):
+            if not isinstance(index, slice):
+                existing = self[index]
+                if existing is not None:
+                    __del(self, existing, None, index)
+                value = __set(self, value, None, index)
+                fn(self, index, value)
+            else:
+                # slice assignment requires __delitem__, insert, __len__
+                step = index.step or 1
+                start = index.start or 0
+                if start < 0:
+                    start += len(self)
+                if index.stop is not None:
+                    stop = index.stop
+                else:
+                    stop = len(self)
+                if stop < 0:
+                    stop += len(self)
+
+                if step == 1:
+                    if value is self:
+                        return
+                    for i in range(start, stop, step):
+                        if len(self) > start:
+                            del self[start]
+
+                    for i, item in enumerate(value):
+                        self.insert(i + start, item)
+                else:
+                    rng = list(range(start, stop, step))
+                    if len(value) != len(rng):
+                        raise ValueError(
+                            "attempt to assign sequence of size %s to "
+                            "extended slice of size %s"
+                            % (len(value), len(rng))
+                        )
+                    for i, item in zip(rng, value):
+                        self.__setitem__(i, item)
+
+        _tidy(__setitem__)
+        return __setitem__
+
+    def __delitem__(fn):
+        def __delitem__(self, index):
+            if not isinstance(index, slice):
+                item = self[index]
+                __del(self, item, None, index)
+                fn(self, index)
+            else:
+                # slice deletion requires __getslice__ and a slice-groking
+                # __getitem__ for stepped deletion
+                # note: not breaking this into atomic dels
+                for item in self[index]:
+                    __del(self, item, None, index)
+                fn(self, index)
+
+        _tidy(__delitem__)
+        return __delitem__
+
+    def extend(fn):
+        def extend(self, iterable):
+            for value in list(iterable):
+                self.append(value)
+
+        _tidy(extend)
+        return extend
+
+    def __iadd__(fn):
+        def __iadd__(self, iterable):
+            # list.__iadd__ takes any iterable and seems to let TypeError
+            # raise as-is instead of returning NotImplemented
+            for value in list(iterable):
+                self.append(value)
+            return self
+
+        _tidy(__iadd__)
+        return __iadd__
+
+    def pop(fn):
+        def pop(self, index=-1):
+            __before_pop(self)
+            item = fn(self, index)
+            __del(self, item, None, index)
+            return item
+
+        _tidy(pop)
+        return pop
+
+    def clear(fn):
+        def clear(self, index=-1):
+            for item in self:
+                __del(self, item, None, index)
+            fn(self)
+
+        _tidy(clear)
+        return clear
+
+    # __imul__ : not wrapping this.  all members of the collection are already
+    # present, so no need to fire appends... wrapping it with an explicit
+    # decorator is still possible, so events on *= can be had if they're
+    # desired.  hard to imagine a use case for __imul__, though.
+
+    l = locals().copy()
+    l.pop("_tidy")
+    return l
+
+
+def _dict_decorators() -> Dict[str, Callable[[_FN], _FN]]:
+    """Tailored instrumentation wrappers for any dict-like mapping class."""
+
+    def _tidy(fn):
+        fn._sa_instrumented = True
+        fn.__doc__ = getattr(dict, fn.__name__).__doc__
+
+    def __setitem__(fn):
+        def __setitem__(self, key, value, _sa_initiator=None):
+            if key in self:
+                __del(self, self[key], _sa_initiator, key)
+            value = __set(self, value, _sa_initiator, key)
+            fn(self, key, value)
+
+        _tidy(__setitem__)
+        return __setitem__
+
+    def __delitem__(fn):
+        def __delitem__(self, key, _sa_initiator=None):
+            if key in self:
+                __del(self, self[key], _sa_initiator, key)
+            fn(self, key)
+
+        _tidy(__delitem__)
+        return __delitem__
+
+    def clear(fn):
+        def clear(self):
+            for key in self:
+                __del(self, self[key], None, key)
+            fn(self)
+
+        _tidy(clear)
+        return clear
+
+    def pop(fn):
+        def pop(self, key, default=NO_ARG):
+            __before_pop(self)
+            _to_del = key in self
+            if default is NO_ARG:
+                item = fn(self, key)
+            else:
+                item = fn(self, key, default)
+            if _to_del:
+                __del(self, item, None, key)
+            return item
+
+        _tidy(pop)
+        return pop
+
+    def popitem(fn):
+        def popitem(self):
+            __before_pop(self)
+            item = fn(self)
+            __del(self, item[1], None, 1)
+            return item
+
+        _tidy(popitem)
+        return popitem
+
+    def setdefault(fn):
+        def setdefault(self, key, default=None):
+            if key not in self:
+                self.__setitem__(key, default)
+                return default
+            else:
+                value = self.__getitem__(key)
+                if value is default:
+                    __set_wo_mutation(self, value, None)
+
+                return value
+
+        _tidy(setdefault)
+        return setdefault
+
+    def update(fn):
+        def update(self, __other=NO_ARG, **kw):
+            if __other is not NO_ARG:
+                if hasattr(__other, "keys"):
+                    for key in list(__other):
+                        if key not in self or self[key] is not __other[key]:
+                            self[key] = __other[key]
+                        else:
+                            __set_wo_mutation(self, __other[key], None)
+                else:
+                    for key, value in __other:
+                        if key not in self or self[key] is not value:
+                            self[key] = value
+                        else:
+                            __set_wo_mutation(self, value, None)
+            for key in kw:
+                if key not in self or self[key] is not kw[key]:
+                    self[key] = kw[key]
+                else:
+                    __set_wo_mutation(self, kw[key], None)
+
+        _tidy(update)
+        return update
+
+    l = locals().copy()
+    l.pop("_tidy")
+    return l
+
+
+_set_binop_bases = (set, frozenset)
+
+
+def _set_binops_check_strict(self: Any, obj: Any) -> bool:
+    """Allow only set, frozenset and self.__class__-derived
+    objects in binops."""
+    return isinstance(obj, _set_binop_bases + (self.__class__,))
+
+
+def _set_binops_check_loose(self: Any, obj: Any) -> bool:
+    """Allow anything set-like to participate in set binops."""
+    return (
+        isinstance(obj, _set_binop_bases + (self.__class__,))
+        or util.duck_type_collection(obj) == set
+    )
+
+
+def _set_decorators() -> Dict[str, Callable[[_FN], _FN]]:
+    """Tailored instrumentation wrappers for any set-like class."""
+
+    def _tidy(fn):
+        fn._sa_instrumented = True
+        fn.__doc__ = getattr(set, fn.__name__).__doc__
+
+    def add(fn):
+        def add(self, value, _sa_initiator=None):
+            if value not in self:
+                value = __set(self, value, _sa_initiator, NO_KEY)
+            else:
+                __set_wo_mutation(self, value, _sa_initiator)
+            # testlib.pragma exempt:__hash__
+            fn(self, value)
+
+        _tidy(add)
+        return add
+
+    def discard(fn):
+        def discard(self, value, _sa_initiator=None):
+            # testlib.pragma exempt:__hash__
+            if value in self:
+                __del(self, value, _sa_initiator, NO_KEY)
+                # testlib.pragma exempt:__hash__
+            fn(self, value)
+
+        _tidy(discard)
+        return discard
+
+    def remove(fn):
+        def remove(self, value, _sa_initiator=None):
+            # testlib.pragma exempt:__hash__
+            if value in self:
+                __del(self, value, _sa_initiator, NO_KEY)
+            # testlib.pragma exempt:__hash__
+            fn(self, value)
+
+        _tidy(remove)
+        return remove
+
+    def pop(fn):
+        def pop(self):
+            __before_pop(self)
+            item = fn(self)
+            # for set in particular, we have no way to access the item
+            # that will be popped before pop is called.
+            __del(self, item, None, NO_KEY)
+            return item
+
+        _tidy(pop)
+        return pop
+
+    def clear(fn):
+        def clear(self):
+            for item in list(self):
+                self.remove(item)
+
+        _tidy(clear)
+        return clear
+
+    def update(fn):
+        def update(self, value):
+            for item in value:
+                self.add(item)
+
+        _tidy(update)
+        return update
+
+    def __ior__(fn):
+        def __ior__(self, value):
+            if not _set_binops_check_strict(self, value):
+                return NotImplemented
+            for item in value:
+                self.add(item)
+            return self
+
+        _tidy(__ior__)
+        return __ior__
+
+    def difference_update(fn):
+        def difference_update(self, value):
+            for item in value:
+                self.discard(item)
+
+        _tidy(difference_update)
+        return difference_update
+
+    def __isub__(fn):
+        def __isub__(self, value):
+            if not _set_binops_check_strict(self, value):
+                return NotImplemented
+            for item in value:
+                self.discard(item)
+            return self
+
+        _tidy(__isub__)
+        return __isub__
+
+    def intersection_update(fn):
+        def intersection_update(self, other):
+            want, have = self.intersection(other), set(self)
+            remove, add = have - want, want - have
+
+            for item in remove:
+                self.remove(item)
+            for item in add:
+                self.add(item)
+
+        _tidy(intersection_update)
+        return intersection_update
+
+    def __iand__(fn):
+        def __iand__(self, other):
+            if not _set_binops_check_strict(self, other):
+                return NotImplemented
+            want, have = self.intersection(other), set(self)
+            remove, add = have - want, want - have
+
+            for item in remove:
+                self.remove(item)
+            for item in add:
+                self.add(item)
+            return self
+
+        _tidy(__iand__)
+        return __iand__
+
+    def symmetric_difference_update(fn):
+        def symmetric_difference_update(self, other):
+            want, have = self.symmetric_difference(other), set(self)
+            remove, add = have - want, want - have
+
+            for item in remove:
+                self.remove(item)
+            for item in add:
+                self.add(item)
+
+        _tidy(symmetric_difference_update)
+        return symmetric_difference_update
+
+    def __ixor__(fn):
+        def __ixor__(self, other):
+            if not _set_binops_check_strict(self, other):
+                return NotImplemented
+            want, have = self.symmetric_difference(other), set(self)
+            remove, add = have - want, want - have
+
+            for item in remove:
+                self.remove(item)
+            for item in add:
+                self.add(item)
+            return self
+
+        _tidy(__ixor__)
+        return __ixor__
+
+    l = locals().copy()
+    l.pop("_tidy")
+    return l
+
+
+class InstrumentedList(List[_T]):
+    """An instrumented version of the built-in list."""
+
+
+class InstrumentedSet(Set[_T]):
+    """An instrumented version of the built-in set."""
+
+
+class InstrumentedDict(Dict[_KT, _VT]):
+    """An instrumented version of the built-in dict."""
+
+
+__canned_instrumentation: util.immutabledict[Any, _CollectionFactoryType] = (
+    util.immutabledict(
+        {
+            list: InstrumentedList,
+            set: InstrumentedSet,
+            dict: InstrumentedDict,
+        }
+    )
+)
+
+__interfaces: util.immutabledict[
+    Any,
+    Tuple[
+        Dict[str, str],
+        Dict[str, Callable[..., Any]],
+    ],
+] = util.immutabledict(
+    {
+        list: (
+            {
+                "appender": "append",
+                "remover": "remove",
+                "iterator": "__iter__",
+            },
+            _list_decorators(),
+        ),
+        set: (
+            {"appender": "add", "remover": "remove", "iterator": "__iter__"},
+            _set_decorators(),
+        ),
+        # decorators are required for dicts and object collections.
+        dict: ({"iterator": "values"}, _dict_decorators()),
+    }
+)
+
+
+def __go(lcls):
+    global keyfunc_mapping, mapped_collection
+    global column_keyed_dict, column_mapped_collection
+    global MappedCollection, KeyFuncDict
+    global attribute_keyed_dict, attribute_mapped_collection
+
+    from .mapped_collection import keyfunc_mapping
+    from .mapped_collection import column_keyed_dict
+    from .mapped_collection import attribute_keyed_dict
+    from .mapped_collection import KeyFuncDict
+
+    from .mapped_collection import mapped_collection
+    from .mapped_collection import column_mapped_collection
+    from .mapped_collection import attribute_mapped_collection
+    from .mapped_collection import MappedCollection
+
+    # ensure instrumentation is associated with
+    # these built-in classes; if a user-defined class
+    # subclasses these and uses @internally_instrumented,
+    # the superclass is otherwise not instrumented.
+    # see [ticket:2406].
+    _instrument_class(InstrumentedList)
+    _instrument_class(InstrumentedSet)
+    _instrument_class(KeyFuncDict)
+
+
+__go(locals())