JezK
Edit File: instrumentation.py
# orm/instrumentation.py # Copyright (C) 2005-2023 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 """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. """ import weakref from . import base from . import collections from . import exc from . import interfaces from . import state from .. import util from ..util import HasMemoized DEL_ATTR = util.symbol("DEL_ATTR") class ClassManager(HasMemoized, 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)) expired_attribute_loader = None "previously known as deferred_scalar_loader" init_method = None factory = None mapper = None declarative_scan = None registry = None @property @util.deprecated( "1.4", message="The ClassManager.deferred_scalar_loader attribute is now " "named expired_attribute_loader", ) def deferred_scalar_loader(self): return self.expired_attribute_loader @deferred_scalar_loader.setter @util.deprecated( "1.4", message="The ClassManager.deferred_scalar_loader attribute is now " "named expired_attribute_loader", ) def deferred_scalar_loader(self, obj): self.expired_attribute_loader = obj def __init__(self, class_): self.class_ = class_ self.info = {} self.new_init = None self.local_attrs = {} self.originals = {} self._finalized = False 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) for basecls in class_.__mro__: mgr = manager_of_class(basecls) if mgr is not None: self.dispatch._update(mgr.dispatch) self.manage() 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 _update_state( self, finalize=False, mapper=None, registry=None, declarative_scan=None, expired_attribute_loader=None, init_method=None, ): if mapper: self.mapper = mapper if registry: registry._add_manager(self) if declarative_scan: self.declarative_scan = weakref.ref(declarative_scan) if expired_attribute_loader: self.expired_attribute_loader = expired_attribute_loader if init_method: assert not self._finalized, ( "class is already instrumented, " "init_method %s can't be applied" % init_method ) self.init_method = init_method if not self._finalized: self.original_init = ( self.init_method if self.init_method is not None and self.class_.__init__ is object.__init__ else self.class_.__init__ ) if finalize and not self._finalized: self._finalize() def _finalize(self): if self._finalized: return self._finalized = True self._instrument_init() _instrumentation_factory.dispatch.class_instrument(self.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__ @HasMemoized.memoized_attribute def _all_key_set(self): return frozenset(self) @HasMemoized.memoized_attribute def _collection_impl_keys(self): return frozenset( [attr.key for attr in self.values() if attr.impl.collection] ) @HasMemoized.memoized_attribute def _scalar_loader_impls(self): return frozenset( [ attr.impl for attr in self.values() if attr.impl.accepts_scalar_loader ] ) @HasMemoized.memoized_attribute def _loader_impls(self): return frozenset([attr.impl for attr in self.values()]) @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. """ return register_class(cls, finalize=False) def _instrument_init(self): self.new_init = _generate_init(self.class_, self, self.original_init) self.install_member("__init__", self.new_init) @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) @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) self._reset_memoizations() 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) self._reset_memoizations() 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.""" for key in list(self.originals): self.uninstall_member(key) self.mapper = self.dispatch = self.new_init = None self.info.clear() for key in list(self): if key in self.local_attrs: self.uninstrument_attribute(key) if self.MANAGER_ATTR in self.class_.__dict__: delattr(self.class_, self.MANAGER_ATTR) 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, self.class_.__dict__.get(key, DEL_ATTR)) setattr(self.class_, key, implementation) def uninstall_member(self, key): original = self.originals.pop(key, None) if original is not DEL_ATTR: setattr(self.class_, key, original) else: delattr(self.class_, key) 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._check_configure() # 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 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() self.dispatch.class_uninstrument(class_) # 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_, finalize=True, mapper=None, registry=None, declarative_scan=None, expired_attribute_loader=None, init_method=None, ): """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_) manager._update_state( mapper=mapper, registry=registry, declarative_scan=declarative_scan, expired_attribute_loader=expired_attribute_loader, init_method=init_method, finalize=finalize, ) 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, original_init): """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. if original_init is None: original_init = class_.__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() env["__name__"] = __name__ 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__