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354 lines
13 KiB
354 lines
13 KiB
4 years ago
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"""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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import logging
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from collections import defaultdict
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from itertools import chain
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from pip._internal.exceptions import (
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BestVersionAlreadyInstalled, DistributionNotFound, HashError, HashErrors,
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UnsupportedPythonVersion,
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)
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from pip._internal.req.constructors import install_req_from_req
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from pip._internal.utils.logging import indent_log
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from pip._internal.utils.misc import dist_in_usersite, ensure_dir
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from pip._internal.utils.packaging import check_dist_requires_python
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logger = logging.getLogger(__name__)
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class Resolver(object):
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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__(self, preparer, session, finder, wheel_cache, use_user_site,
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ignore_dependencies, ignore_installed, ignore_requires_python,
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force_reinstall, isolated, upgrade_strategy):
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super(Resolver, self).__init__()
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assert upgrade_strategy in self._allowed_strategies
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self.preparer = preparer
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self.finder = finder
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self.session = session
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# NOTE: This would eventually be replaced with a cache that can give
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# information about both sdist and wheels transparently.
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self.wheel_cache = wheel_cache
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self.require_hashes = None # This is set in resolve
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self.upgrade_strategy = upgrade_strategy
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self.force_reinstall = force_reinstall
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self.isolated = isolated
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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._discovered_dependencies = defaultdict(list)
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def resolve(self, requirement_set):
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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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# make the wheelhouse
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if self.preparer.wheel_download_dir:
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ensure_dir(self.preparer.wheel_download_dir)
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# If any top-level requirement has a hash specified, enter
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# hash-checking mode, which requires hashes from all.
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root_reqs = (
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requirement_set.unnamed_requirements +
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list(requirement_set.requirements.values())
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)
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self.require_hashes = (
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requirement_set.require_hashes or
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any(req.has_hash_options for req in root_reqs)
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)
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# Display where finder is looking for packages
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locations = self.finder.get_formatted_locations()
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if locations:
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logger.info(locations)
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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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# req.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 = []
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hash_errors = HashErrors()
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for req in chain(root_reqs, discovered_reqs):
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try:
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discovered_reqs.extend(
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self._resolve_one(requirement_set, req)
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)
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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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def _is_upgrade_allowed(self, req):
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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.is_direct
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def _set_req_to_reinstall(self, req):
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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 dist_in_usersite(req.satisfied_by):
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req.conflicts_with = req.satisfied_by
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req.satisfied_by = None
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# XXX: Stop passing requirement_set for options
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def _check_skip_installed(self, req_to_install):
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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 _get_abstract_dist_for(self, req):
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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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assert self.require_hashes is not None, (
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"require_hashes should have been set in Resolver.resolve()"
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)
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if req.editable:
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return self.preparer.prepare_editable_requirement(
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req, self.require_hashes, self.use_user_site, self.finder,
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)
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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(
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req, self.require_hashes, skip_reason
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)
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upgrade_allowed = self._is_upgrade_allowed(req)
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abstract_dist = self.preparer.prepare_linked_requirement(
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req, self.session, self.finder, upgrade_allowed,
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self.require_hashes
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)
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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" or
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self.force_reinstall or
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self.ignore_installed or
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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):'
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' %s', req,
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)
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return abstract_dist
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def _resolve_one(self, requirement_set, req_to_install):
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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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# register tmp src for cleanup in case something goes wrong
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requirement_set.reqs_to_cleanup.append(req_to_install)
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abstract_dist = self._get_abstract_dist_for(req_to_install)
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# Parse and return dependencies
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dist = abstract_dist.dist(self.finder)
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try:
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check_dist_requires_python(dist)
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except UnsupportedPythonVersion as err:
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if self.ignore_requires_python:
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logger.warning(err.args[0])
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else:
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raise
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more_reqs = []
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def add_req(subreq, extras_requested):
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sub_install_req = install_req_from_req(
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str(subreq),
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req_to_install,
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isolated=self.isolated,
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wheel_cache=self.wheel_cache,
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)
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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(
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add_to_parent
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)
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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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req_to_install.is_direct = True
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requirement_set.add_requirement(
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req_to_install, parent_req_name=None,
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)
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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.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 does not provide the extra \'%s\'',
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dist, missing
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)
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available_requested = sorted(
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set(dist.extras) & set(req_to_install.extras)
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)
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for subreq in dist.requires(available_requested):
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add_req(subreq, extras_requested=available_requested)
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if not req_to_install.editable and not req_to_install.satisfied_by:
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# XXX: --no-install leads this to report 'Successfully
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# downloaded' for only non-editable reqs, even though we took
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# action on them.
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requirement_set.successfully_downloaded.append(req_to_install)
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return more_reqs
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def get_installation_order(self, req_set):
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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()
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def schedule(req):
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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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