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"""Validation of dependencies of packages"""
 
 import logging
 from typing import Callable, Dict, List, NamedTuple, Optional, Set, Tuple
 
 from pip._vendor.packaging.requirements import Requirement
 from pip._vendor.packaging.utils import NormalizedName, canonicalize_name
 
 from pip._internal.distributions import make_distribution_for_install_requirement
 from pip._internal.metadata import get_default_environment
 from pip._internal.metadata.base import DistributionVersion
 from pip._internal.req.req_install import InstallRequirement
 
 logger = logging.getLogger(__name__)
 
 
 class PackageDetails(NamedTuple):
 version: DistributionVersion
 dependencies: List[Requirement]
 
 
 # Shorthands
 PackageSet = Dict[NormalizedName, PackageDetails]
 Missing = Tuple[NormalizedName, Requirement]
 Conflicting = Tuple[NormalizedName, DistributionVersion, Requirement]
 
 MissingDict = Dict[NormalizedName, List[Missing]]
 ConflictingDict = Dict[NormalizedName, List[Conflicting]]
 CheckResult = Tuple[MissingDict, ConflictingDict]
 ConflictDetails = Tuple[PackageSet, CheckResult]
 
 
 def create_package_set_from_installed() -> Tuple[PackageSet, bool]:
 """Converts a list of distributions into a PackageSet."""
 package_set = {}
 problems = False
 env = get_default_environment()
 for dist in env.iter_installed_distributions(local_only=False, skip=()):
 name = dist.canonical_name
 try:
 dependencies = list(dist.iter_dependencies())
 package_set[name] = PackageDetails(dist.version, dependencies)
 except (OSError, ValueError) as e:
 # Don't crash on unreadable or broken metadata.
 logger.warning("Error parsing requirements for %s: %s", name, e)
 problems = True
 return package_set, problems
 
 
 def check_package_set(
 package_set: PackageSet, should_ignore: Optional[Callable[[str], bool]] = None
 ) -> CheckResult:
 """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.
 """
 
 missing = {}
 conflicting = {}
 
 for package_name, package_detail in package_set.items():
 # Info about dependencies of package_name
 missing_deps: Set[Missing] = set()
 conflicting_deps: Set[Conflicting] = set()
 
 if should_ignore and should_ignore(package_name):
 continue
 
 for req in package_detail.dependencies:
 name = canonicalize_name(req.name)
 
 # 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
 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: List[InstallRequirement]) -> ConflictDetails:
 """For checking if the dependency graph would be consistent after \
 installing given requirements
 """
 # 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: List[InstallRequirement], package_set: PackageSet
 ) -> Set[NormalizedName]:
 """Computes the version of packages after installing to_install."""
 # 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_metadata_distribution()
 name = dist.canonical_name
 package_set[name] = PackageDetails(dist.version, list(dist.iter_dependencies()))
 
 installed.add(name)
 
 return installed
 
 
 def _create_whitelist(
 would_be_installed: Set[NormalizedName], package_set: PackageSet
 ) -> Set[NormalizedName]:
 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].dependencies:
 if canonicalize_name(req.name) in packages_affected:
 packages_affected.add(package_name)
 break
 
 return packages_affected
 
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