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"""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.utils.logging import indent_log
from pip._internal.utils.misc import (
dist_in_install_path,
dist_in_usersite,
ensure_dir,
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 Callable, DefaultDict, List, Optional, Set, Tuple
from pip._vendor import pkg_resources
from pip._internal.distributions import AbstractDistribution
from pip._internal.network.session import PipSession
from pip._internal.index import PackageFinder
from pip._internal.operations.prepare import RequirementPreparer
from pip._internal.req.req_install import InstallRequirement
from pip._internal.req.req_set import RequirementSet
InstallRequirementProvider = Callable[
[str, InstallRequirement], 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,
))
class Resolver(object):
"""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
session, # type: PipSession
finder, # type: PackageFinder
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.session = session
# This is set in resolve
self.require_hashes = None # type: Optional[bool]
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: DefaultDict[str, List]
def resolve(self, requirement_set):
# type: (RequirementSet) -> None
"""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.
"""
# make the wheelhouse
if self.preparer.wheel_download_dir:
ensure_dir(self.preparer.wheel_download_dir)
# If any top-level requirement has a hash specified, enter
# hash-checking mode, which requires hashes from all.
root_reqs = (
requirement_set.unnamed_requirements +
list(requirement_set.requirements.values())
)
self.require_hashes = (
requirement_set.require_hashes or
any(req.has_hash_options for req in root_reqs)
)
# Display where finder is looking for packages
search_scope = self.finder.search_scope
locations = search_scope.get_formatted_locations()
if locations:
logger.info(locations)
# Actually prepare the files, and collect any exceptions. Most hash
# exceptions cannot be checked ahead of time, because
# req.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(root_reqs, 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
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.is_direct
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))
and dist_in_install_path(req.satisfied_by)):
req.conflicts_with = req.satisfied_by
req.satisfied_by = None
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
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.
"""
assert self.require_hashes is not None, (
"require_hashes should have been set in Resolver.resolve()"
)
if req.editable:
return self.preparer.prepare_editable_requirement(
req, self.require_hashes, self.use_user_site, self.finder,
)
# 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, self.require_hashes, skip_reason
)
upgrade_allowed = self._is_upgrade_allowed(req)
# We eagerly populate the link, since that's our "legacy" behavior.
req.populate_link(self.finder, upgrade_allowed, self.require_hashes)
abstract_dist = self.preparer.prepare_linked_requirement(
req, self.session, self.finder, self.require_hashes
)
# 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
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
# register tmp src for cleanup in case something goes wrong
requirement_set.reqs_to_cleanup.append(req_to_install)
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
req_to_install.is_direct = True
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.
requirement_set.successfully_downloaded.append(req_to_install)
return more_reqs
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