Currently, SageMath hardcodes the metaclasses DynamicMetaclass, DynamicClasscallMetaclass, DynamicInheritComparisonMetaclass, DynamicInheritComparisonClasscallMetaclass, NestedClassMetaclass, InheritComparisonMetaclass, and InheritComparisonClasscallMetaclass.

Apparently, they are all based on few single-purpose metaclasses (DynamicMetaclass, InheritComparisonMetaclass, NestedClassMetaclass and ClasscallMetaclass), and the hardcoded combinations exist because Python doesn't allow much freedom when providing different metaclasses in the bases of a class definition. And apparently several combinations are missing.

The purpose of this ticket is to allow for an automatic creation of combined metaclasses, so that only the single-purpose metaclasses need to be implemented, and all other metaclasses will be created dynamically.

The approach is by introducing a meta-metaclass SageMetaclass --- i.e., any metaclass in Sage is instance of SageMetaclass.

Component: refactoring

Keywords: metaclass dynamic

Branch/Commit: u/SimonKing/metaclass_framework @ 4d493e0

Issue created by migration from https://trac.sagemath.org/ticket/21681