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