text: # 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
  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:
              self.registry = registry
          if declarative_scan:
              self.declarative_scan = 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)
  
      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)
          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)
  
      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._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
  
          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_,
      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()
      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__
  