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