<h2>Editing File: /usr/lib/python3.8/site-packages/pip/_internal/operations/check.py</h2><form method='post'><textarea name='content' class='file-edit'>&quot;&quot;&quot;Validation of dependencies of packages
&quot;&quot;&quot;

# The following comment should be removed at some point in the future.
# mypy: strict-optional=False
# mypy: disallow-untyped-defs=False

import logging
from collections import namedtuple

from pip._vendor.packaging.utils import canonicalize_name
from pip._vendor.pkg_resources import RequirementParseError

from pip._internal.distributions import (
    make_distribution_for_install_requirement,
)
from pip._internal.utils.misc import get_installed_distributions
from pip._internal.utils.typing import MYPY_CHECK_RUNNING

logger = logging.getLogger(__name__)

if MYPY_CHECK_RUNNING:
    from pip._internal.req.req_install import InstallRequirement
    from typing import (
        Any, Callable, Dict, Optional, Set, Tuple, List
    )

    # Shorthands
    PackageSet = Dict[str, 'PackageDetails']
    Missing = Tuple[str, Any]
    Conflicting = Tuple[str, str, Any]

    MissingDict = Dict[str, List[Missing]]
    ConflictingDict = Dict[str, List[Conflicting]]
    CheckResult = Tuple[MissingDict, ConflictingDict]

PackageDetails = namedtuple('PackageDetails', ['version', 'requires'])


def create_package_set_from_installed(**kwargs):
    # type: (**Any) -&gt; Tuple[PackageSet, bool]
    &quot;&quot;&quot;Converts a list of distributions into a PackageSet.
    &quot;&quot;&quot;
    # Default to using all packages installed on the system
    if kwargs == {}:
        kwargs = {&quot;local_only&quot;: False, &quot;skip&quot;: ()}

    package_set = {}
    problems = False
    for dist in get_installed_distributions(**kwargs):
        name = canonicalize_name(dist.project_name)
        try:
            package_set[name] = PackageDetails(dist.version, dist.requires())
        except RequirementParseError as e:
            # Don't crash on broken metadata
            logging.warning(&quot;Error parsing requirements for %s: %s&quot;, name, e)
            problems = True
    return package_set, problems


def check_package_set(package_set, should_ignore=None):
    # type: (PackageSet, Optional[Callable[[str], bool]]) -&gt; CheckResult
    &quot;&quot;&quot;Check if a package set is consistent

    If should_ignore is passed, it should be a callable that takes a
    package name and returns a boolean.
    &quot;&quot;&quot;
    if should_ignore is None:
        def should_ignore(name):
            return False

    missing = {}
    conflicting = {}

    for package_name in package_set:
        # Info about dependencies of package_name
        missing_deps = set()  # type: Set[Missing]
        conflicting_deps = set()  # type: Set[Conflicting]

        if should_ignore(package_name):
            continue

        for req in package_set[package_name].requires:
            name = canonicalize_name(req.project_name)  # type: str

            # Check if it's missing
            if name not in package_set:
                missed = True
                if req.marker is not None:
                    missed = req.marker.evaluate()
                if missed:
                    missing_deps.add((name, req))
                continue

            # Check if there's a conflict
            version = package_set[name].version  # type: str
            if not req.specifier.contains(version, prereleases=True):
                conflicting_deps.add((name, version, req))

        if missing_deps:
            missing[package_name] = sorted(missing_deps, key=str)
        if conflicting_deps:
            conflicting[package_name] = sorted(conflicting_deps, key=str)

    return missing, conflicting


def check_install_conflicts(to_install):
    # type: (List[InstallRequirement]) -&gt; Tuple[PackageSet, CheckResult]
    &quot;&quot;&quot;For checking if the dependency graph would be consistent after \
    installing given requirements
    &quot;&quot;&quot;
    # Start from the current state
    package_set, _ = create_package_set_from_installed()
    # Install packages
    would_be_installed = _simulate_installation_of(to_install, package_set)

    # Only warn about directly-dependent packages; create a whitelist of them
    whitelist = _create_whitelist(would_be_installed, package_set)

    return (
        package_set,
        check_package_set(
            package_set, should_ignore=lambda name: name not in whitelist
        )
    )


def _simulate_installation_of(to_install, package_set):
    # type: (List[InstallRequirement], PackageSet) -&gt; Set[str]
    &quot;&quot;&quot;Computes the version of packages after installing to_install.
    &quot;&quot;&quot;

    # Keep track of packages that were installed
    installed = set()

    # Modify it as installing requirement_set would (assuming no errors)
    for inst_req in to_install:
        abstract_dist = make_distribution_for_install_requirement(inst_req)
        dist = abstract_dist.get_pkg_resources_distribution()

        name = canonicalize_name(dist.key)
        package_set[name] = PackageDetails(dist.version, dist.requires())

        installed.add(name)

    return installed


def _create_whitelist(would_be_installed, package_set):
    # type: (Set[str], PackageSet) -&gt; Set[str]
    packages_affected = set(would_be_installed)

    for package_name in package_set:
        if package_name in packages_affected:
            continue

        for req in package_set[package_name].requires:
            if canonicalize_name(req.name) in packages_affected:
                packages_affected.add(package_name)
                break

    return packages_affected
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