Hi folks, The PEP 487 implementation included some changes to the way the implicit __class__ cell is initialised in order to allow zero-argument super() to work properly in class methods called from __set_name__ and __init_subclass__ implementations.
Unfortunately, the specific implementation chosen turned out to have an obscure incompatibility with certain custom metaclasses, notably including the metaclass for Model objects in Django. While there's a patch pending to fix the incompatibility in Django, this should really be a deprecation warning on the CPython side, rather than an abrupt compatibility break. The latest patches attached to issue 23722 partially revert the previous changes, and update the data model documentation to cover the new constraints on custom metaclass implementations that want to support zero-argument super(): * http://bugs.python.org/issue23722#msg282317 Aside from the unintentional backwards compatibility break, the main reason this is a release blocker is that in order to detect the problematic case, we need to revert some of the changes previously made to the bytecode generated for class statements (some opcodes had been dropped as no longer needed, but now we need them again for error detection purposes). Regards, Nick. -- Nick Coghlan | ncogh...@gmail.com | Brisbane, Australia _______________________________________________ python-committers mailing list python-committers@python.org https://mail.python.org/mailman/listinfo/python-committers Code of Conduct: https://www.python.org/psf/codeofconduct/
