156 lines
5.6 KiB
Python
156 lines
5.6 KiB
Python
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"""Utilities to lazily create and visit candidates found.
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Creating and visiting a candidate is a *very* costly operation. It involves
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fetching, extracting, potentially building modules from source, and verifying
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distribution metadata. It is therefore crucial for performance to keep
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everything here lazy all the way down, so we only touch candidates that we
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absolutely need, and not "download the world" when we only need one version of
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something.
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"""
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import functools
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from collections.abc import Sequence
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from typing import TYPE_CHECKING, Any, Callable, Iterator, Optional, Set, Tuple
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from pip._vendor.packaging.version import _BaseVersion
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from .base import Candidate
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IndexCandidateInfo = Tuple[_BaseVersion, Callable[[], Optional[Candidate]]]
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if TYPE_CHECKING:
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SequenceCandidate = Sequence[Candidate]
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else:
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# For compatibility: Python before 3.9 does not support using [] on the
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# Sequence class.
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#
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# >>> from collections.abc import Sequence
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# >>> Sequence[str]
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# Traceback (most recent call last):
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# File "<stdin>", line 1, in <module>
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# TypeError: 'ABCMeta' object is not subscriptable
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#
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# TODO: Remove this block after dropping Python 3.8 support.
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SequenceCandidate = Sequence
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def _iter_built(infos: Iterator[IndexCandidateInfo]) -> Iterator[Candidate]:
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"""Iterator for ``FoundCandidates``.
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This iterator is used when the package is not already installed. Candidates
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from index come later in their normal ordering.
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"""
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versions_found: Set[_BaseVersion] = set()
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for version, func in infos:
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if version in versions_found:
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continue
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candidate = func()
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if candidate is None:
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continue
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yield candidate
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versions_found.add(version)
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def _iter_built_with_prepended(
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installed: Candidate, infos: Iterator[IndexCandidateInfo]
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) -> Iterator[Candidate]:
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"""Iterator for ``FoundCandidates``.
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This iterator is used when the resolver prefers the already-installed
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candidate and NOT to upgrade. The installed candidate is therefore
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always yielded first, and candidates from index come later in their
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normal ordering, except skipped when the version is already installed.
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"""
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yield installed
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versions_found: Set[_BaseVersion] = {installed.version}
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for version, func in infos:
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if version in versions_found:
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continue
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candidate = func()
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if candidate is None:
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continue
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yield candidate
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versions_found.add(version)
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def _iter_built_with_inserted(
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installed: Candidate, infos: Iterator[IndexCandidateInfo]
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) -> Iterator[Candidate]:
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"""Iterator for ``FoundCandidates``.
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This iterator is used when the resolver prefers to upgrade an
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already-installed package. Candidates from index are returned in their
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normal ordering, except replaced when the version is already installed.
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The implementation iterates through and yields other candidates, inserting
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the installed candidate exactly once before we start yielding older or
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equivalent candidates, or after all other candidates if they are all newer.
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"""
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versions_found: Set[_BaseVersion] = set()
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for version, func in infos:
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if version in versions_found:
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continue
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# If the installed candidate is better, yield it first.
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if installed.version >= version:
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yield installed
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versions_found.add(installed.version)
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candidate = func()
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if candidate is None:
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continue
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yield candidate
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versions_found.add(version)
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# If the installed candidate is older than all other candidates.
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if installed.version not in versions_found:
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yield installed
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class FoundCandidates(SequenceCandidate):
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"""A lazy sequence to provide candidates to the resolver.
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The intended usage is to return this from `find_matches()` so the resolver
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can iterate through the sequence multiple times, but only access the index
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page when remote packages are actually needed. This improve performances
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when suitable candidates are already installed on disk.
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"""
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def __init__(
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self,
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get_infos: Callable[[], Iterator[IndexCandidateInfo]],
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installed: Optional[Candidate],
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prefers_installed: bool,
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incompatible_ids: Set[int],
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):
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self._get_infos = get_infos
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self._installed = installed
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self._prefers_installed = prefers_installed
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self._incompatible_ids = incompatible_ids
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def __getitem__(self, index: Any) -> Any:
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# Implemented to satisfy the ABC check. This is not needed by the
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# resolver, and should not be used by the provider either (for
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# performance reasons).
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raise NotImplementedError("don't do this")
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def __iter__(self) -> Iterator[Candidate]:
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infos = self._get_infos()
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if not self._installed:
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iterator = _iter_built(infos)
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elif self._prefers_installed:
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iterator = _iter_built_with_prepended(self._installed, infos)
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else:
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iterator = _iter_built_with_inserted(self._installed, infos)
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return (c for c in iterator if id(c) not in self._incompatible_ids)
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def __len__(self) -> int:
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# Implemented to satisfy the ABC check. This is not needed by the
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# resolver, and should not be used by the provider either (for
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# performance reasons).
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raise NotImplementedError("don't do this")
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@functools.lru_cache(maxsize=1)
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def __bool__(self) -> bool:
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if self._prefers_installed and self._installed:
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return True
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return any(self)
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