from __future__ import annotations from typing import Collection, Generic, Iterable, Iterator from ..structs import CT, RT, RequirementInformation class Criterion(Generic[RT, CT]): """Representation of possible resolution results of a package. This holds three attributes: * `information` is a collection of `RequirementInformation` pairs. Each pair is a requirement contributing to this criterion, and the candidate that provides the requirement. * `incompatibilities` is a collection of all known not-to-work candidates to exclude from consideration. * `candidates` is a collection containing all possible candidates deducted from the union of contributing requirements and known incompatibilities. It should never be empty, except when the criterion is an attribute of a raised `RequirementsConflicted` (in which case it is always empty). .. note:: This class is intended to be externally immutable. **Do not** mutate any of its attribute containers. """ def __init__( self, candidates: Iterable[CT], information: Collection[RequirementInformation[RT, CT]], incompatibilities: Collection[CT], ) -> None: self.candidates = candidates self.information = information self.incompatibilities = incompatibilities def __repr__(self) -> str: requirements = ", ".join( f"({req!r}, via={parent!r})" for req, parent in self.information ) return f"Criterion({requirements})" def iter_requirement(self) -> Iterator[RT]: return (i.requirement for i in self.information) def iter_parent(self) -> Iterator[CT | None]: return (i.parent for i in self.information)