468 lines
18 KiB
Python
468 lines
18 KiB
Python
"""Dependency Resolution
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The dependency resolution in pip is performed as follows:
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for top-level requirements:
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a. only one spec allowed per project, regardless of conflicts or not.
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otherwise a "double requirement" exception is raised
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b. they override sub-dependency requirements.
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for sub-dependencies
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a. "first found, wins" (where the order is breadth first)
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"""
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# The following comment should be removed at some point in the future.
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# mypy: strict-optional=False
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import logging
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import sys
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from collections import defaultdict
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from itertools import chain
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from typing import DefaultDict, Iterable, List, Optional, Set, Tuple
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from pip._vendor.packaging import specifiers
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from pip._vendor.packaging.requirements import Requirement
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from pip._internal.cache import WheelCache
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from pip._internal.exceptions import (
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BestVersionAlreadyInstalled,
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DistributionNotFound,
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HashError,
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HashErrors,
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NoneMetadataError,
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UnsupportedPythonVersion,
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)
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from pip._internal.index.package_finder import PackageFinder
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from pip._internal.metadata import BaseDistribution
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from pip._internal.models.link import Link
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from pip._internal.operations.prepare import RequirementPreparer
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from pip._internal.req.req_install import (
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InstallRequirement,
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check_invalid_constraint_type,
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)
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from pip._internal.req.req_set import RequirementSet
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from pip._internal.resolution.base import BaseResolver, InstallRequirementProvider
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from pip._internal.utils.compatibility_tags import get_supported
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from pip._internal.utils.logging import indent_log
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from pip._internal.utils.misc import normalize_version_info
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from pip._internal.utils.packaging import check_requires_python
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logger = logging.getLogger(__name__)
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DiscoveredDependencies = DefaultDict[str, List[InstallRequirement]]
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def _check_dist_requires_python(
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dist: BaseDistribution,
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version_info: Tuple[int, int, int],
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ignore_requires_python: bool = False,
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) -> None:
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"""
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Check whether the given Python version is compatible with a distribution's
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"Requires-Python" value.
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:param version_info: A 3-tuple of ints representing the Python
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major-minor-micro version to check.
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:param ignore_requires_python: Whether to ignore the "Requires-Python"
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value if the given Python version isn't compatible.
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:raises UnsupportedPythonVersion: When the given Python version isn't
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compatible.
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"""
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# This idiosyncratically converts the SpecifierSet to str and let
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# check_requires_python then parse it again into SpecifierSet. But this
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# is the legacy resolver so I'm just not going to bother refactoring.
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try:
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requires_python = str(dist.requires_python)
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except FileNotFoundError as e:
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raise NoneMetadataError(dist, str(e))
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try:
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is_compatible = check_requires_python(
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requires_python,
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version_info=version_info,
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)
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except specifiers.InvalidSpecifier as exc:
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logger.warning(
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"Package %r has an invalid Requires-Python: %s", dist.raw_name, exc
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)
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return
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if is_compatible:
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return
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version = ".".join(map(str, version_info))
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if ignore_requires_python:
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logger.debug(
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"Ignoring failed Requires-Python check for package %r: %s not in %r",
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dist.raw_name,
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version,
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requires_python,
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)
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return
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raise UnsupportedPythonVersion(
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"Package {!r} requires a different Python: {} not in {!r}".format(
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dist.raw_name, version, requires_python
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)
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)
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class Resolver(BaseResolver):
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"""Resolves which packages need to be installed/uninstalled to perform \
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the requested operation without breaking the requirements of any package.
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"""
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_allowed_strategies = {"eager", "only-if-needed", "to-satisfy-only"}
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def __init__(
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self,
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preparer: RequirementPreparer,
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finder: PackageFinder,
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wheel_cache: Optional[WheelCache],
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make_install_req: InstallRequirementProvider,
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use_user_site: bool,
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ignore_dependencies: bool,
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ignore_installed: bool,
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ignore_requires_python: bool,
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force_reinstall: bool,
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upgrade_strategy: str,
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py_version_info: Optional[Tuple[int, ...]] = None,
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) -> None:
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super().__init__()
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assert upgrade_strategy in self._allowed_strategies
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if py_version_info is None:
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py_version_info = sys.version_info[:3]
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else:
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py_version_info = normalize_version_info(py_version_info)
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self._py_version_info = py_version_info
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self.preparer = preparer
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self.finder = finder
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self.wheel_cache = wheel_cache
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self.upgrade_strategy = upgrade_strategy
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self.force_reinstall = force_reinstall
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self.ignore_dependencies = ignore_dependencies
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self.ignore_installed = ignore_installed
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self.ignore_requires_python = ignore_requires_python
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self.use_user_site = use_user_site
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self._make_install_req = make_install_req
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self._discovered_dependencies: DiscoveredDependencies = defaultdict(list)
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def resolve(
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self, root_reqs: List[InstallRequirement], check_supported_wheels: bool
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) -> RequirementSet:
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"""Resolve what operations need to be done
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As a side-effect of this method, the packages (and their dependencies)
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are downloaded, unpacked and prepared for installation. This
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preparation is done by ``pip.operations.prepare``.
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Once PyPI has static dependency metadata available, it would be
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possible to move the preparation to become a step separated from
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dependency resolution.
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"""
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requirement_set = RequirementSet(check_supported_wheels=check_supported_wheels)
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for req in root_reqs:
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if req.constraint:
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check_invalid_constraint_type(req)
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requirement_set.add_requirement(req)
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# Actually prepare the files, and collect any exceptions. Most hash
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# exceptions cannot be checked ahead of time, because
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# _populate_link() needs to be called before we can make decisions
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# based on link type.
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discovered_reqs: List[InstallRequirement] = []
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hash_errors = HashErrors()
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for req in chain(requirement_set.all_requirements, discovered_reqs):
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try:
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discovered_reqs.extend(self._resolve_one(requirement_set, req))
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except HashError as exc:
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exc.req = req
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hash_errors.append(exc)
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if hash_errors:
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raise hash_errors
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return requirement_set
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def _is_upgrade_allowed(self, req: InstallRequirement) -> bool:
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if self.upgrade_strategy == "to-satisfy-only":
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return False
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elif self.upgrade_strategy == "eager":
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return True
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else:
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assert self.upgrade_strategy == "only-if-needed"
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return req.user_supplied or req.constraint
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def _set_req_to_reinstall(self, req: InstallRequirement) -> None:
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"""
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Set a requirement to be installed.
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"""
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# Don't uninstall the conflict if doing a user install and the
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# conflict is not a user install.
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if not self.use_user_site or req.satisfied_by.in_usersite:
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req.should_reinstall = True
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req.satisfied_by = None
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def _check_skip_installed(
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self, req_to_install: InstallRequirement
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) -> Optional[str]:
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"""Check if req_to_install should be skipped.
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This will check if the req is installed, and whether we should upgrade
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or reinstall it, taking into account all the relevant user options.
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After calling this req_to_install will only have satisfied_by set to
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None if the req_to_install is to be upgraded/reinstalled etc. Any
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other value will be a dist recording the current thing installed that
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satisfies the requirement.
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Note that for vcs urls and the like we can't assess skipping in this
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routine - we simply identify that we need to pull the thing down,
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then later on it is pulled down and introspected to assess upgrade/
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reinstalls etc.
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:return: A text reason for why it was skipped, or None.
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"""
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if self.ignore_installed:
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return None
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req_to_install.check_if_exists(self.use_user_site)
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if not req_to_install.satisfied_by:
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return None
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if self.force_reinstall:
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self._set_req_to_reinstall(req_to_install)
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return None
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if not self._is_upgrade_allowed(req_to_install):
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if self.upgrade_strategy == "only-if-needed":
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return "already satisfied, skipping upgrade"
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return "already satisfied"
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# Check for the possibility of an upgrade. For link-based
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# requirements we have to pull the tree down and inspect to assess
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# the version #, so it's handled way down.
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if not req_to_install.link:
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try:
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self.finder.find_requirement(req_to_install, upgrade=True)
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except BestVersionAlreadyInstalled:
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# Then the best version is installed.
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return "already up-to-date"
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except DistributionNotFound:
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# No distribution found, so we squash the error. It will
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# be raised later when we re-try later to do the install.
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# Why don't we just raise here?
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pass
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self._set_req_to_reinstall(req_to_install)
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return None
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def _find_requirement_link(self, req: InstallRequirement) -> Optional[Link]:
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upgrade = self._is_upgrade_allowed(req)
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best_candidate = self.finder.find_requirement(req, upgrade)
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if not best_candidate:
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return None
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# Log a warning per PEP 592 if necessary before returning.
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link = best_candidate.link
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if link.is_yanked:
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reason = link.yanked_reason or "<none given>"
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msg = (
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# Mark this as a unicode string to prevent
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# "UnicodeEncodeError: 'ascii' codec can't encode character"
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# in Python 2 when the reason contains non-ascii characters.
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"The candidate selected for download or install is a "
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"yanked version: {candidate}\n"
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"Reason for being yanked: {reason}"
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).format(candidate=best_candidate, reason=reason)
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logger.warning(msg)
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return link
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def _populate_link(self, req: InstallRequirement) -> None:
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"""Ensure that if a link can be found for this, that it is found.
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Note that req.link may still be None - if the requirement is already
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installed and not needed to be upgraded based on the return value of
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_is_upgrade_allowed().
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If preparer.require_hashes is True, don't use the wheel cache, because
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cached wheels, always built locally, have different hashes than the
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files downloaded from the index server and thus throw false hash
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mismatches. Furthermore, cached wheels at present have undeterministic
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contents due to file modification times.
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"""
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if req.link is None:
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req.link = self._find_requirement_link(req)
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if self.wheel_cache is None or self.preparer.require_hashes:
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return
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cache_entry = self.wheel_cache.get_cache_entry(
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link=req.link,
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package_name=req.name,
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supported_tags=get_supported(),
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)
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if cache_entry is not None:
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logger.debug("Using cached wheel link: %s", cache_entry.link)
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if req.link is req.original_link and cache_entry.persistent:
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req.original_link_is_in_wheel_cache = True
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req.link = cache_entry.link
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def _get_dist_for(self, req: InstallRequirement) -> BaseDistribution:
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"""Takes a InstallRequirement and returns a single AbstractDist \
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representing a prepared variant of the same.
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"""
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if req.editable:
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return self.preparer.prepare_editable_requirement(req)
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# satisfied_by is only evaluated by calling _check_skip_installed,
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# so it must be None here.
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assert req.satisfied_by is None
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skip_reason = self._check_skip_installed(req)
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if req.satisfied_by:
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return self.preparer.prepare_installed_requirement(req, skip_reason)
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# We eagerly populate the link, since that's our "legacy" behavior.
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self._populate_link(req)
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dist = self.preparer.prepare_linked_requirement(req)
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# NOTE
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# The following portion is for determining if a certain package is
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# going to be re-installed/upgraded or not and reporting to the user.
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# This should probably get cleaned up in a future refactor.
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# req.req is only avail after unpack for URL
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# pkgs repeat check_if_exists to uninstall-on-upgrade
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# (#14)
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if not self.ignore_installed:
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req.check_if_exists(self.use_user_site)
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if req.satisfied_by:
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should_modify = (
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self.upgrade_strategy != "to-satisfy-only"
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or self.force_reinstall
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or self.ignore_installed
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or req.link.scheme == "file"
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)
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if should_modify:
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self._set_req_to_reinstall(req)
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else:
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logger.info(
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"Requirement already satisfied (use --upgrade to upgrade): %s",
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req,
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)
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return dist
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def _resolve_one(
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self,
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requirement_set: RequirementSet,
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req_to_install: InstallRequirement,
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) -> List[InstallRequirement]:
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"""Prepare a single requirements file.
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:return: A list of additional InstallRequirements to also install.
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"""
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# Tell user what we are doing for this requirement:
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# obtain (editable), skipping, processing (local url), collecting
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# (remote url or package name)
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if req_to_install.constraint or req_to_install.prepared:
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return []
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req_to_install.prepared = True
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# Parse and return dependencies
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dist = self._get_dist_for(req_to_install)
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# This will raise UnsupportedPythonVersion if the given Python
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# version isn't compatible with the distribution's Requires-Python.
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_check_dist_requires_python(
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dist,
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version_info=self._py_version_info,
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ignore_requires_python=self.ignore_requires_python,
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)
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more_reqs: List[InstallRequirement] = []
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def add_req(subreq: Requirement, extras_requested: Iterable[str]) -> None:
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# This idiosyncratically converts the Requirement to str and let
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# make_install_req then parse it again into Requirement. But this is
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# the legacy resolver so I'm just not going to bother refactoring.
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sub_install_req = self._make_install_req(str(subreq), req_to_install)
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parent_req_name = req_to_install.name
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to_scan_again, add_to_parent = requirement_set.add_requirement(
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sub_install_req,
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parent_req_name=parent_req_name,
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extras_requested=extras_requested,
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)
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if parent_req_name and add_to_parent:
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self._discovered_dependencies[parent_req_name].append(add_to_parent)
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more_reqs.extend(to_scan_again)
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with indent_log():
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# We add req_to_install before its dependencies, so that we
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# can refer to it when adding dependencies.
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if not requirement_set.has_requirement(req_to_install.name):
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# 'unnamed' requirements will get added here
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# 'unnamed' requirements can only come from being directly
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# provided by the user.
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assert req_to_install.user_supplied
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requirement_set.add_requirement(req_to_install, parent_req_name=None)
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if not self.ignore_dependencies:
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if req_to_install.extras:
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logger.debug(
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"Installing extra requirements: %r",
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",".join(req_to_install.extras),
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)
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missing_requested = sorted(
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set(req_to_install.extras) - set(dist.iter_provided_extras())
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)
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for missing in missing_requested:
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logger.warning(
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"%s %s does not provide the extra '%s'",
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dist.raw_name,
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dist.version,
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missing,
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)
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available_requested = sorted(
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set(dist.iter_provided_extras()) & set(req_to_install.extras)
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)
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for subreq in dist.iter_dependencies(available_requested):
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add_req(subreq, extras_requested=available_requested)
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return more_reqs
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def get_installation_order(
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self, req_set: RequirementSet
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) -> List[InstallRequirement]:
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"""Create the installation order.
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The installation order is topological - requirements are installed
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before the requiring thing. We break cycles at an arbitrary point,
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and make no other guarantees.
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"""
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# The current implementation, which we may change at any point
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# installs the user specified things in the order given, except when
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# dependencies must come earlier to achieve topological order.
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order = []
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ordered_reqs: Set[InstallRequirement] = set()
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def schedule(req: InstallRequirement) -> None:
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if req.satisfied_by or req in ordered_reqs:
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return
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if req.constraint:
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return
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ordered_reqs.add(req)
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for dep in self._discovered_dependencies[req.name]:
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schedule(dep)
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order.append(req)
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for install_req in req_set.requirements.values():
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schedule(install_req)
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return order
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