Calculates the method resolution order for a given class *cls*. Includes relevant abstract base classes (with their respective bases) from the *types* iterable. Uses a modified C3 linearization algorithm.
(cls, types)
| 730 | ) |
| 731 | |
| 732 | def _compose_mro(cls, types): |
| 733 | """Calculates the method resolution order for a given class *cls*. |
| 734 | |
| 735 | Includes relevant abstract base classes (with their respective bases) from |
| 736 | the *types* iterable. Uses a modified C3 linearization algorithm. |
| 737 | |
| 738 | """ |
| 739 | bases = set(cls.__mro__) |
| 740 | # Remove entries which are already present in the __mro__ or unrelated. |
| 741 | def is_related(typ): |
| 742 | return (typ not in bases and hasattr(typ, '__mro__') |
| 743 | and not isinstance(typ, GenericAlias) |
| 744 | and issubclass(cls, typ)) |
| 745 | types = [n for n in types if is_related(n)] |
| 746 | # Remove entries which are strict bases of other entries (they will end up |
| 747 | # in the MRO anyway. |
| 748 | def is_strict_base(typ): |
| 749 | for other in types: |
| 750 | if typ != other and typ in other.__mro__: |
| 751 | return True |
| 752 | return False |
| 753 | types = [n for n in types if not is_strict_base(n)] |
| 754 | # Subclasses of the ABCs in *types* which are also implemented by |
| 755 | # *cls* can be used to stabilize ABC ordering. |
| 756 | type_set = set(types) |
| 757 | mro = [] |
| 758 | for typ in types: |
| 759 | found = [] |
| 760 | for sub in typ.__subclasses__(): |
| 761 | if sub not in bases and issubclass(cls, sub): |
| 762 | found.append([s for s in sub.__mro__ if s in type_set]) |
| 763 | if not found: |
| 764 | mro.append(typ) |
| 765 | continue |
| 766 | # Favor subclasses with the biggest number of useful bases |
| 767 | found.sort(key=len, reverse=True) |
| 768 | for sub in found: |
| 769 | for subcls in sub: |
| 770 | if subcls not in mro: |
| 771 | mro.append(subcls) |
| 772 | return _c3_mro(cls, abcs=mro) |
| 773 | |
| 774 | def _find_impl(cls, registry): |
| 775 | """Returns the best matching implementation from *registry* for type *cls*. |
no test coverage detected