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# orm/instrumentation.py
# Copyright (C) 2005-2021 the SQLAlchemy authors and contributors
# <see AUTHORS file>
#
# This module is part of SQLAlchemy and is released under
# the MIT License: http://www.opensource.org/licenses/mit-license.php
"""Defines SQLAlchemy's system of class instrumentation.
This module is usually not directly visible to user applications, but
defines a large part of the ORM's interactivity.
instrumentation.py deals with registration of end-user classes
for state tracking. It interacts closely with state.py
and attributes.py which establish per-instance and per-class-attribute
instrumentation, respectively.
The class instrumentation system can be customized on a per-class
or global basis using the :mod:`sqlalchemy.ext.instrumentation`
module, which provides the means to build and specify
alternate instrumentation forms.
.. versionchanged: 0.8
The instrumentation extension system was moved out of the
ORM and into the external :mod:`sqlalchemy.ext.instrumentation`
package. When that package is imported, it installs
itself within sqlalchemy.orm so that its more comprehensive
resolution mechanics take effect.
"""
from . import base
from . import collections
from . import exc
from . import interfaces
from . import state
from .. import util
_memoized_key_collection = util.group_expirable_memoized_property()
class ClassManager(dict):
"""Tracks state information at the class level."""
MANAGER_ATTR = base.DEFAULT_MANAGER_ATTR
STATE_ATTR = base.DEFAULT_STATE_ATTR
_state_setter = staticmethod(util.attrsetter(STATE_ATTR))
deferred_scalar_loader = None
original_init = object.__init__
factory = None
def __init__(self, class_):
self.class_ = class_
self.info = {}
self.new_init = None
self.local_attrs = {}
self.originals = {}
self._bases = [
mgr
for mgr in [
manager_of_class(base)
for base in self.class_.__bases__
if isinstance(base, type)
]
if mgr is not None
]
for base_ in self._bases:
self.update(base_)
self.dispatch._events._new_classmanager_instance(class_, self)
# events._InstanceEventsHold.populate(class_, self)
for basecls in class_.__mro__:
mgr = manager_of_class(basecls)
if mgr is not None:
self.dispatch._update(mgr.dispatch)
self.manage()
self._instrument_init()
if "__del__" in class_.__dict__:
util.warn(
"__del__() method on class %s will "
"cause unreachable cycles and memory leaks, "
"as SQLAlchemy instrumentation often creates "
"reference cycles. Please remove this method." % class_
)
def __hash__(self):
return id(self)
def __eq__(self, other):
return other is self
@property
def is_mapped(self):
return "mapper" in self.__dict__
@_memoized_key_collection
def _all_key_set(self):
return frozenset(self)
@_memoized_key_collection
def _collection_impl_keys(self):
return frozenset(
[attr.key for attr in self.values() if attr.impl.collection]
)
@_memoized_key_collection
def _scalar_loader_impls(self):
return frozenset(
[
attr.impl
for attr in self.values()
if attr.impl.accepts_scalar_loader
]
)
@util.memoized_property
def mapper(self):
# raises unless self.mapper has been assigned
raise exc.UnmappedClassError(self.class_)
def _all_sqla_attributes(self, exclude=None):
"""return an iterator of all classbound attributes that are
implement :class:`.InspectionAttr`.
This includes :class:`.QueryableAttribute` as well as extension
types such as :class:`.hybrid_property` and
:class:`.AssociationProxy`.
"""
found = {}
# constraints:
# 1. yield keys in cls.__dict__ order
# 2. if a subclass has the same key as a superclass, include that
# key as part of the ordering of the superclass, because an
# overridden key is usually installed by the mapper which is going
# on a different ordering
# 3. don't use getattr() as this fires off descriptors
for supercls in self.class_.__mro__[0:-1]:
inherits = supercls.__mro__[1]
for key in supercls.__dict__:
found.setdefault(key, supercls)
if key in inherits.__dict__:
continue
val = found[key].__dict__[key]
if (
isinstance(val, interfaces.InspectionAttr)
and val.is_attribute
):
yield key, val
def _get_class_attr_mro(self, key, default=None):
"""return an attribute on the class without tripping it."""
for supercls in self.class_.__mro__:
if key in supercls.__dict__:
return supercls.__dict__[key]
else:
return default
def _attr_has_impl(self, key):
"""Return True if the given attribute is fully initialized.
i.e. has an impl.
"""
return key in self and self[key].impl is not None
def _subclass_manager(self, cls):
"""Create a new ClassManager for a subclass of this ClassManager's
class.
This is called automatically when attributes are instrumented so that
the attributes can be propagated to subclasses against their own
class-local manager, without the need for mappers etc. to have already
pre-configured managers for the full class hierarchy. Mappers
can post-configure the auto-generated ClassManager when needed.
"""
manager = manager_of_class(cls)
if manager is None:
manager = _instrumentation_factory.create_manager_for_cls(cls)
return manager
def _instrument_init(self):
# TODO: self.class_.__init__ is often the already-instrumented
# __init__ from an instrumented superclass. We still need to make
# our own wrapper, but it would
# be nice to wrap the original __init__ and not our existing wrapper
# of such, since this adds method overhead.
self.original_init = self.class_.__init__
self.new_init = _generate_init(self.class_, self)
self.install_member("__init__", self.new_init)
def _uninstrument_init(self):
if self.new_init:
self.uninstall_member("__init__")
self.new_init = None
@util.memoized_property
def _state_constructor(self):
self.dispatch.first_init(self, self.class_)
return state.InstanceState
def manage(self):
"""Mark this instance as the manager for its class."""
setattr(self.class_, self.MANAGER_ATTR, self)
def dispose(self):
"""Disassociate this manager from its class."""
delattr(self.class_, self.MANAGER_ATTR)
@util.hybridmethod
def manager_getter(self):
return _default_manager_getter
@util.hybridmethod
def state_getter(self):
"""Return a (instance) -> InstanceState callable.
"state getter" callables should raise either KeyError or
AttributeError if no InstanceState could be found for the
instance.
"""
return _default_state_getter
@util.hybridmethod
def dict_getter(self):
return _default_dict_getter
def instrument_attribute(self, key, inst, propagated=False):
if propagated:
if key in self.local_attrs:
return # don't override local attr with inherited attr
else:
self.local_attrs[key] = inst
self.install_descriptor(key, inst)
_memoized_key_collection.expire_instance(self)
self[key] = inst
for cls in self.class_.__subclasses__():
manager = self._subclass_manager(cls)
manager.instrument_attribute(key, inst, True)
def subclass_managers(self, recursive):
for cls in self.class_.__subclasses__():
mgr = manager_of_class(cls)
if mgr is not None and mgr is not self:
yield mgr
if recursive:
for m in mgr.subclass_managers(True):
yield m
def post_configure_attribute(self, key):
_instrumentation_factory.dispatch.attribute_instrument(
self.class_, key, self[key]
)
def uninstrument_attribute(self, key, propagated=False):
if key not in self:
return
if propagated:
if key in self.local_attrs:
return # don't get rid of local attr
else:
del self.local_attrs[key]
self.uninstall_descriptor(key)
_memoized_key_collection.expire_instance(self)
del self[key]
for cls in self.class_.__subclasses__():
manager = manager_of_class(cls)
if manager:
manager.uninstrument_attribute(key, True)
def unregister(self):
"""remove all instrumentation established by this ClassManager."""
self._uninstrument_init()
self.mapper = self.dispatch = None
self.info.clear()
for key in list(self):
if key in self.local_attrs:
self.uninstrument_attribute(key)
def install_descriptor(self, key, inst):
if key in (self.STATE_ATTR, self.MANAGER_ATTR):
raise KeyError(
"%r: requested attribute name conflicts with "
"instrumentation attribute of the same name." % key
)
setattr(self.class_, key, inst)
def uninstall_descriptor(self, key):
delattr(self.class_, key)
def install_member(self, key, implementation):
if key in (self.STATE_ATTR, self.MANAGER_ATTR):
raise KeyError(
"%r: requested attribute name conflicts with "
"instrumentation attribute of the same name." % key
)
self.originals.setdefault(key, getattr(self.class_, key, None))
setattr(self.class_, key, implementation)
def uninstall_member(self, key):
original = self.originals.pop(key, None)
if original is not None:
setattr(self.class_, key, original)
def instrument_collection_class(self, key, collection_class):
return collections.prepare_instrumentation(collection_class)
def initialize_collection(self, key, state, factory):
user_data = factory()
adapter = collections.CollectionAdapter(
self.get_impl(key), state, user_data
)
return adapter, user_data
def is_instrumented(self, key, search=False):
if search:
return key in self
else:
return key in self.local_attrs
def get_impl(self, key):
return self[key].impl
@property
def attributes(self):
return iter(self.values())
# InstanceState management
def new_instance(self, state=None):
instance = self.class_.__new__(self.class_)
if state is None:
state = self._state_constructor(instance, self)
self._state_setter(instance, state)
return instance
def setup_instance(self, instance, state=None):
if state is None:
state = self._state_constructor(instance, self)
self._state_setter(instance, state)
def teardown_instance(self, instance):
delattr(instance, self.STATE_ATTR)
def _serialize(self, state, state_dict):
return _SerializeManager(state, state_dict)
def _new_state_if_none(self, instance):
"""Install a default InstanceState if none is present.
A private convenience method used by the __init__ decorator.
"""
if hasattr(instance, self.STATE_ATTR):
return False
elif self.class_ is not instance.__class__ and self.is_mapped:
# this will create a new ClassManager for the
# subclass, without a mapper. This is likely a
# user error situation but allow the object
# to be constructed, so that it is usable
# in a non-ORM context at least.
return self._subclass_manager(
instance.__class__
)._new_state_if_none(instance)
else:
state = self._state_constructor(instance, self)
self._state_setter(instance, state)
return state
def has_state(self, instance):
return hasattr(instance, self.STATE_ATTR)
def has_parent(self, state, key, optimistic=False):
"""TODO"""
return self.get_impl(key).hasparent(state, optimistic=optimistic)
def __bool__(self):
"""All ClassManagers are non-zero regardless of attribute state."""
return True
__nonzero__ = __bool__
def __repr__(self):
return "<%s of %r at %x>" % (
self.__class__.__name__,
self.class_,
id(self),
)
class _SerializeManager(object):
"""Provide serialization of a :class:`.ClassManager`.
The :class:`.InstanceState` uses ``__init__()`` on serialize
and ``__call__()`` on deserialize.
"""
def __init__(self, state, d):
self.class_ = state.class_
manager = state.manager
manager.dispatch.pickle(state, d)
def __call__(self, state, inst, state_dict):
state.manager = manager = manager_of_class(self.class_)
if manager is None:
raise exc.UnmappedInstanceError(
inst,
"Cannot deserialize object of type %r - "
"no mapper() has "
"been configured for this class within the current "
"Python process!" % self.class_,
)
elif manager.is_mapped and not manager.mapper.configured:
manager.mapper._configure_all()
# setup _sa_instance_state ahead of time so that
# unpickle events can access the object normally.
# see [ticket:2362]
if inst is not None:
manager.setup_instance(inst, state)
manager.dispatch.unpickle(state, state_dict)
class InstrumentationFactory(object):
"""Factory for new ClassManager instances."""
def create_manager_for_cls(self, class_):
assert class_ is not None
assert manager_of_class(class_) is None
# give a more complicated subclass
# a chance to do what it wants here
manager, factory = self._locate_extended_factory(class_)
if factory is None:
factory = ClassManager
manager = factory(class_)
self._check_conflicts(class_, factory)
manager.factory = factory
self.dispatch.class_instrument(class_)
return manager
def _locate_extended_factory(self, class_):
"""Overridden by a subclass to do an extended lookup."""
return None, None
def _check_conflicts(self, class_, factory):
"""Overridden by a subclass to test for conflicting factories."""
return
def unregister(self, class_):
manager = manager_of_class(class_)
manager.unregister()
manager.dispose()
self.dispatch.class_uninstrument(class_)
if ClassManager.MANAGER_ATTR in class_.__dict__:
delattr(class_, ClassManager.MANAGER_ATTR)
# this attribute is replaced by sqlalchemy.ext.instrumentation
# when imported.
_instrumentation_factory = InstrumentationFactory()
# these attributes are replaced by sqlalchemy.ext.instrumentation
# when a non-standard InstrumentationManager class is first
# used to instrument a class.
instance_state = _default_state_getter = base.instance_state
instance_dict = _default_dict_getter = base.instance_dict
manager_of_class = _default_manager_getter = base.manager_of_class
def register_class(class_):
"""Register class instrumentation.
Returns the existing or newly created class manager.
"""
manager = manager_of_class(class_)
if manager is None:
manager = _instrumentation_factory.create_manager_for_cls(class_)
return manager
def unregister_class(class_):
"""Unregister class instrumentation."""
_instrumentation_factory.unregister(class_)
def is_instrumented(instance, key):
"""Return True if the given attribute on the given instance is
instrumented by the attributes package.
This function may be used regardless of instrumentation
applied directly to the class, i.e. no descriptors are required.
"""
return manager_of_class(instance.__class__).is_instrumented(
key, search=True
)
def _generate_init(class_, class_manager):
"""Build an __init__ decorator that triggers ClassManager events."""
# TODO: we should use the ClassManager's notion of the
# original '__init__' method, once ClassManager is fixed
# to always reference that.
original__init__ = class_.__init__
assert original__init__
# Go through some effort here and don't change the user's __init__
# calling signature, including the unlikely case that it has
# a return value.
# FIXME: need to juggle local names to avoid constructor argument
# clashes.
func_body = """\
def __init__(%(apply_pos)s):
new_state = class_manager._new_state_if_none(%(self_arg)s)
if new_state:
return new_state._initialize_instance(%(apply_kw)s)
else:
return original__init__(%(apply_kw)s)
"""
func_vars = util.format_argspec_init(original__init__, grouped=False)
func_text = func_body % func_vars
if util.py2k:
func = getattr(original__init__, "im_func", original__init__)
func_defaults = getattr(func, "func_defaults", None)
else:
func_defaults = getattr(original__init__, "__defaults__", None)
func_kw_defaults = getattr(original__init__, "__kwdefaults__", None)
env = locals().copy()
exec(func_text, env)
__init__ = env["__init__"]
__init__.__doc__ = original__init__.__doc__
__init__._sa_original_init = original__init__
if func_defaults:
__init__.__defaults__ = func_defaults
if not util.py2k and func_kw_defaults:
__init__.__kwdefaults__ = func_kw_defaults
return __init__