when using :class:`.AbstractConcreteBase` in conjunction with a subclass that declares ``__abstract__``. fixes #3185
that are now affixed to _MapperConfig - declarative now creates column copies ahead of time so that they are ready to go for a declared_attr - overhaul of declared_attr; memoization, cascading modifier - A relationship set up with :class:`.declared_attr` on a :class:`.AbstractConcreteBase` base class will now be configured on the abstract base mapping automatically, in addition to being set up on descendant concrete classes as usual. fixes #2670 - The :class:`.declared_attr` construct has newly improved behaviors and features in conjunction with declarative. The decorated function will now have access to the final column copies present on the local mixin when invoked, and will also be invoked exactly once for each mapped class, the returned result being memoized. A new modifier :attr:`.declared_attr.cascading` is added as well. fixes #3150 - the original plan for #3150 has been scaled back; by copying mixin columns up front and memoizing, we don't actually need the "map properties later" thing. - full docs + migration notes
to get all flake8 passing
fully usable within declarative relationship configuration, as its string classname would not be available in the registry of classnames at mapper configuration time. The class now explicitly adds itself to the class regsitry, and additionally both :class:`.AbstractConcreteBase` as well as :class:`.ConcreteBase` set themselves up *before* mappers are configured within the :func:`.configure_mappers` setup, using the new :meth:`.MapperEvents.before_configured` event. [ticket:2950] - Added new :meth:`.MapperEvents.before_configured` event which allows an event at the start of :func:`.configure_mappers`, as well as ``__declare_first__()`` hook within declarative to complement ``__declare_last__()``. - modified how after_configured is invoked; we just make a dispatch() not actually connected to any mapper. this makes it easier to also invoke before_configured correctly. - improved the ComparableEntity fixture to handle collections that are sets.
:class:`.DeferredReflection` to define classes pending for reflection, if some subset of those classes were discarded before the :meth:`.DeferredReflection.prepare` method were called to reflect and map the class, a strong reference to the class would remain held within the declarative internals. This internal collection of "classes to map" now uses weak references against the classes themselves.
automatic reflection support for the "secondary" table referred to by a :func:`.relationship`. "secondary", when specified either as a string table name, or as a :class:`.Table` object with only a name and :class:`.MetaData` object will also be included in the reflection process when :meth:`.DeferredReflection.prepare` is called. [ticket:2865] - clsregistry._resolver() now uses a stateful _class_resolver() class in order to handle the work of mapping strings to objects. This is to provide for simpler extensibility, namely a ._resolvers collection of ad-hoc name resolution functions; the DeferredReflection class adds its own resolver here in order to handle relationship(secondary) names which generate new Table objects.