# -*- coding: utf-8 -*-
__all__ = ['Distribution']

import io
import sys
import re
import os
import warnings
import numbers
import distutils.log
import distutils.core
import distutils.cmd
import distutils.dist
from distutils.util import strtobool
from distutils.debug import DEBUG
from distutils.fancy_getopt import translate_longopt
import itertools

from collections import defaultdict
from email import message_from_file

from distutils.errors import DistutilsOptionError, DistutilsSetupError
from distutils.util import rfc822_escape
from distutils.version import StrictVersion

from setuptools.extern import packaging
from setuptools.extern import ordered_set

from . import SetuptoolsDeprecationWarning

import setuptools
from setuptools import windows_support
from setuptools.monkey import get_unpatched
from setuptools.config import parse_configuration
import pkg_resources

__import__('setuptools.extern.packaging.specifiers')
__import__('setuptools.extern.packaging.version')


def _get_unpatched(cls):
    warnings.warn("Do not call this function", DistDeprecationWarning)
    return get_unpatched(cls)


def get_metadata_version(self):
    mv = getattr(self, 'metadata_version', None)

    if mv is None:
        if self.long_description_content_type or self.provides_extras:
            mv = StrictVersion('2.1')
        elif (self.maintainer is not None or
              self.maintainer_email is not None or
              getattr(self, 'python_requires', None) is not None or
              self.project_urls):
            mv = StrictVersion('1.2')
        elif (self.provides or self.requires or self.obsoletes or
                self.classifiers or self.download_url):
            mv = StrictVersion('1.1')
        else:
            mv = StrictVersion('1.0')

        self.metadata_version = mv

    return mv


def read_pkg_file(self, file):
    """Reads the metadata values from a file object."""
    msg = message_from_file(file)

    def _read_field(name):
        value = msg[name]
        if value == 'UNKNOWN':
            return None
        return value

    def _read_list(name):
        values = msg.get_all(name, None)
        if values == []:
            return None
        return values

    self.metadata_version = StrictVersion(msg['metadata-version'])
    self.name = _read_field('name')
    self.version = _read_field('version')
    self.description = _read_field('summary')
    # we are filling author only.
    self.author = _read_field('author')
    self.maintainer = None
    self.author_email = _read_field('author-email')
    self.maintainer_email = None
    self.url = _read_field('home-page')
    self.license = _read_field('license')

    if 'download-url' in msg:
        self.download_url = _read_field('download-url')
    else:
        self.download_url = None

    self.long_description = _read_field('description')
    self.description = _read_field('summary')

    if 'keywords' in msg:
        self.keywords = _read_field('keywords').split(',')

    self.platforms = _read_list('platform')
    self.classifiers = _read_list('classifier')

    # PEP 314 - these fields only exist in 1.1
    if self.metadata_version == StrictVersion('1.1'):
        self.requires = _read_list('requires')
        self.provides = _read_list('provides')
        self.obsoletes = _read_list('obsoletes')
    else:
        self.requires = None
        self.provides = None
        self.obsoletes = None


def single_line(val):
    # quick and dirty validation for description pypa/setuptools#1390
    if '\n' in val:
        raise ValueError("newlines not allowed")
    return val


# Based on Python 3.5 version
def write_pkg_file(self, file):  # noqa: C901  # is too complex (14)  # FIXME
    """Write the PKG-INFO format data to a file object.
    """
    version = self.get_metadata_version()

    def write_field(key, value):
        file.write("%s: %s\n" % (key, value))

    write_field('Metadata-Version', str(version))
    write_field('Name', self.get_name())
    write_field('Version', self.get_version())
    write_field('Summary', single_line(self.get_description()))
    write_field('Home-page', self.get_url())

    if version < StrictVersion('1.2'):
        write_field('Author', self.get_contact())
        write_field('Author-email', self.get_contact_email())
    else:
        optional_fields = (
            ('Author', 'author'),
            ('Author-email', 'author_email'),
            ('Maintainer', 'maintainer'),
            ('Maintainer-email', 'maintainer_email'),
        )

        for field, attr in optional_fields:
            attr_val = getattr(self, attr)

            if attr_val is not None:
                write_field(field, attr_val)

    write_field('License', self.get_license())
    if self.download_url:
        write_field('Download-URL', self.download_url)
    for project_url in self.project_urls.items():
        write_field('Project-URL', '%s, %s' % project_url)

    long_desc = rfc822_escape(self.get_long_description())
    write_field('Description', long_desc)

    keywords = ','.join(self.get_keywords())
    if keywords:
        write_field('Keywords', keywords)

    if version >= StrictVersion('1.2'):
        for platform in self.get_platforms():
            write_field('Platform', platform)
    else:
        self._write_list(file, 'Platform', self.get_platforms())

    self._write_list(file, 'Classifier', self.get_classifiers())

    # PEP 314
    self._write_list(file, 'Requires', self.get_requires())
    self._write_list(file, 'Provides', self.get_provides())
    self._write_list(file, 'Obsoletes', self.get_obsoletes())

    # Setuptools specific for PEP 345
    if hasattr(self, 'python_requires'):
        write_field('Requires-Python', self.python_requires)

    # PEP 566
    if self.long_description_content_type:
        write_field(
            'Description-Content-Type',
            self.long_description_content_type
        )
    if self.provides_extras:
        for extra in self.provides_extras:
            write_field('Provides-Extra', extra)


sequence = tuple, list


def check_importable(dist, attr, value):
    try:
        ep = pkg_resources.EntryPoint.parse('x=' + value)
        assert not ep.extras
    except (TypeError, ValueError, AttributeError, AssertionError) as e:
        raise DistutilsSetupError(
            "%r must be importable 'module:attrs' string (got %r)"
            % (attr, value)
        ) from e


def assert_string_list(dist, attr, value):
    """Verify that value is a string list"""
    try:
        # verify that value is a list or tuple to exclude unordered
        # or single-use iterables
        assert isinstance(value, (list, tuple))
        # verify that elements of value are strings
        assert ''.join(value) != value
    except (TypeError, ValueError, AttributeError, AssertionError) as e:
        raise DistutilsSetupError(
            "%r must be a list of strings (got %r)" % (attr, value)
        ) from e


def check_nsp(dist, attr, value):
    """Verify that namespace packages are valid"""
    ns_packages = value
    assert_string_list(dist, attr, ns_packages)
    for nsp in ns_packages:
        if not dist.has_contents_for(nsp):
            raise DistutilsSetupError(
                "Distribution contains no modules or packages for " +
                "namespace package %r" % nsp
            )
        parent, sep, child = nsp.rpartition('.')
        if parent and parent not in ns_packages:
            distutils.log.warn(
                "WARNING: %r is declared as a package namespace, but %r"
                " is not: please correct this in setup.py", nsp, parent
            )


def check_extras(dist, attr, value):
    """Verify that extras_require mapping is valid"""
    try:
        list(itertools.starmap(_check_extra, value.items()))
    except (TypeError, ValueError, AttributeError) as e:
        raise DistutilsSetupError(
            "'extras_require' must be a dictionary whose values are "
            "strings or lists of strings containing valid project/version "
            "requirement specifiers."
        ) from e


def _check_extra(extra, reqs):
    name, sep, marker = extra.partition(':')
    if marker and pkg_resources.invalid_marker(marker):
        raise DistutilsSetupError("Invalid environment marker: " + marker)
    list(pkg_resources.parse_requirements(reqs))


def assert_bool(dist, attr, value):
    """Verify that value is True, False, 0, or 1"""
    if bool(value) != value:
        tmpl = "{attr!r} must be a boolean value (got {value!r})"
        raise DistutilsSetupError(tmpl.format(attr=attr, value=value))


def check_requirements(dist, attr, value):
    """Verify that install_requires is a valid requirements list"""
    try:
        list(pkg_resources.parse_requirements(value))
        if isinstance(value, (dict, set)):
            raise TypeError("Unordered types are not allowed")
    except (TypeError, ValueError) as error:
        tmpl = (
            "{attr!r} must be a string or list of strings "
            "containing valid project/version requirement specifiers; {error}"
        )
        raise DistutilsSetupError(
            tmpl.format(attr=attr, error=error)
        ) from error


def check_specifier(dist, attr, value):
    """Verify that value is a valid version specifier"""
    try:
        packaging.specifiers.SpecifierSet(value)
    except packaging.specifiers.InvalidSpecifier as error:
        tmpl = (
            "{attr!r} must be a string "
            "containing valid version specifiers; {error}"
        )
        raise DistutilsSetupError(
            tmpl.format(attr=attr, error=error)
        ) from error


def check_entry_points(dist, attr, value):
    """Verify that entry_points map is parseable"""
    try:
        pkg_resources.EntryPoint.parse_map(value)
    except ValueError as e:
        raise DistutilsSetupError(e) from e


def check_test_suite(dist, attr, value):
    if not isinstance(value, str):
        raise DistutilsSetupError("test_suite must be a string")


def check_package_data(dist, attr, value):
    """Verify that value is a dictionary of package names to glob lists"""
    if not isinstance(value, dict):
        raise DistutilsSetupError(
            "{!r} must be a dictionary mapping package names to lists of "
            "string wildcard patterns".format(attr))
    for k, v in value.items():
        if not isinstance(k, str):
            raise DistutilsSetupError(
                "keys of {!r} dict must be strings (got {!r})"
                .format(attr, k)
            )
        assert_string_list(dist, 'values of {!r} dict'.format(attr), v)


def check_packages(dist, attr, value):
    for pkgname in value:
        if not re.match(r'\w+(\.\w+)*', pkgname):
            distutils.log.warn(
                "WARNING: %r not a valid package name; please use only "
                ".-separated package names in setup.py", pkgname
            )


_Distribution = get_unpatched(distutils.core.Distribution)


class Distribution(_Distribution):
    """Distribution with support for tests and package data

    This is an enhanced version of 'distutils.dist.Distribution' that
    effectively adds the following new optional keyword arguments to 'setup()':

     'install_requires' -- a string or sequence of strings specifying project
        versions that the distribution requires when installed, in the format
        used by 'pkg_resources.require()'.  They will be installed
        automatically when the package is installed.  If you wish to use
        packages that are not available in PyPI, or want to give your users an
        alternate download location, you can add a 'find_links' option to the
        '[easy_install]' section of your project's 'setup.cfg' file, and then
        setuptools will scan the listed web pages for links that satisfy the
        requirements.

     'extras_require' -- a dictionary mapping names of optional "extras" to the
        additional requirement(s) that using those extras incurs. For example,
        this::

            extras_require = dict(reST = ["docutils>=0.3", "reSTedit"])

        indicates that the distribution can optionally provide an extra
        capability called "reST", but it can only be used if docutils and
        reSTedit are installed.  If the user installs your package using
        EasyInstall and requests one of your extras, the corresponding
        additional requirements will be installed if needed.

     'test_suite' -- the name of a test suite to run for the 'test' command.
        If the user runs 'python setup.py test', the package will be installed,
        and the named test suite will be run.  The format is the same as
        would be used on a 'unittest.py' command line.  That is, it is the
        dotted name of an object to import and call to generate a test suite.

     'package_data' -- a dictionary mapping package names to lists of filenames
        or globs to use to find data files contained in the named packages.
        If the dictionary has filenames or globs listed under '""' (the empty
        string), those names will be searched for in every package, in addition
        to any names for the specific package.  Data files found using these
        names/globs will be installed along with the package, in the same
        location as the package.  Note that globs are allowed to reference
        the contents of non-package subdirectories, as long as you use '/' as
        a path separator.  (Globs are automatically converted to
        platform-specific paths at runtime.)

    In addition to these new keywords, this class also has several new methods
    for manipulating the distribution's contents.  For example, the 'include()'
    and 'exclude()' methods can be thought of as in-place add and subtract
    commands that add or remove packages, modules, extensions, and so on from
    the distribution.
    """

    _DISTUTILS_UNSUPPORTED_METADATA = {
        'long_description_content_type': None,
        'project_urls': dict,
        'provides_extras': ordered_set.OrderedSet,
        'license_files': ordered_set.OrderedSet,
    }

    _patched_dist = None

    def patch_missing_pkg_info(self, attrs):
        # Fake up a replacement for the data that would normally come from
        # PKG-INFO, but which might not yet be built if this is a fresh
        # checkout.
        #
        if not attrs or 'name' not in attrs or 'version' not in attrs:
            return
        key = pkg_resources.safe_name(str(attrs['name'])).lower()
        dist = pkg_resources.working_set.by_key.get(key)
        if dist is not None and not dist.has_metadata('PKG-INFO'):
            dist._version = pkg_resources.safe_version(str(attrs['version']))
            self._patched_dist = dist

    def __init__(self, attrs=None):
        have_package_data = hasattr(self, "package_data")
        if not have_package_data:
            self.package_data = {}
        attrs = attrs or {}
        self.dist_files = []
        # Filter-out setuptools' specific options.
        self.src_root = attrs.pop("src_root", None)
        self.patch_missing_pkg_info(attrs)
        self.dependency_links = attrs.pop('dependency_links', [])
        self.setup_requires = attrs.pop('setup_requires', [])
        for ep in pkg_resources.iter_entry_points('distutils.setup_keywords'):
            vars(self).setdefault(ep.name, None)
        _Distribution.__init__(self, {
            k: v for k, v in attrs.items()
            if k not in self._DISTUTILS_UNSUPPORTED_METADATA
        })

        # Fill-in missing metadata fields not supported by distutils.
        # Note some fields may have been set by other tools (e.g. pbr)
        # above; they are taken preferrentially to setup() arguments
        for option, default in self._DISTUTILS_UNSUPPORTED_METADATA.items():
            for source in self.metadata.__dict__, attrs:
                if option in source:
                    value = source[option]
                    break
            else:
                value = default() if default else None
            setattr(self.metadata, option, value)

        self.metadata.version = self._normalize_version(
            self._validate_version(self.metadata.version))
        self._finalize_requires()

    @staticmethod
    def _normalize_version(version):
        if isinstance(version, setuptools.sic) or version is None:
            return version

        normalized = str(packaging.version.Version(version))
        if version != normalized:
            tmpl = "Normalizing '{version}' to '{normalized}'"
            warnings.warn(tmpl.format(**locals()))
            return normalized
        return version

    @staticmethod
    def _validate_version(version):
        if isinstance(version, numbers.Number):
            # Some people apparently take "version number" too literally :)
            version = str(version)

        if version is not None:
            try:
                packaging.version.Version(version)
            except (packaging.version.InvalidVersion, TypeError):
                warnings.warn(
                    "The version specified (%r) is an invalid version, this "
                    "may not work as expected with newer versions of "
                    "setuptools, pip, and PyPI. Please see PEP 440 for more "
                    "details." % version
                )
                return setuptools.sic(version)
        return version

    def _finalize_requires(self):
        """
        Set `metadata.python_requires` and fix environment markers
        in `install_requires` and `extras_require`.
        """
        if getattr(self, 'python_requires', None):
            self.metadata.python_requires = self.python_requires

        if getattr(self, 'extras_require', None):
            for extra in self.extras_require.keys():
                # Since this gets called multiple times at points where the
                # keys have become 'converted' extras, ensure that we are only
                # truly adding extras we haven't seen before here.
                extra = extra.split(':')[0]
                if extra:
                    self.metadata.provides_extras.add(extra)

        self._convert_extras_requirements()
        self._move_install_requirements_markers()

    def _convert_extras_requirements(self):
        """
        Convert requirements in `extras_require` of the form
        `"extra": ["barbazquux; {marker}"]` to
        `"extra:{marker}": ["barbazquux"]`.
        """
        spec_ext_reqs = getattr(self, 'extras_require', None) or {}
        self._tmp_extras_require = defaultdict(list)
        for section, v in spec_ext_reqs.items():
            # Do not strip empty sections.
            self._tmp_extras_require[section]
            for r in pkg_resources.parse_requirements(v):
                suffix = self._suffix_for(r)
                self._tmp_extras_require[section + suffix].append(r)

    @staticmethod
    def _suffix_for(req):
        """
        For a requirement, return the 'extras_require' suffix for
        that requirement.
        """
        return ':' + str(req.marker) if req.marker else ''

    def _move_install_requirements_markers(self):
        """
        Move requirements in `install_requires` that are using environment
        markers `extras_require`.
        """

        # divide the install_requires into two sets, simple ones still
        # handled by install_requires and more complex ones handled
        # by extras_require.

        def is_simple_req(req):
            return not req.marker

        spec_inst_reqs = getattr(self, 'install_requires', None) or ()
        inst_reqs = list(pkg_resources.parse_requirements(spec_inst_reqs))
        simple_reqs = filter(is_simple_req, inst_reqs)
        complex_reqs = itertools.filterfalse(is_simple_req, inst_reqs)
        self.install_requires = list(map(str, simple_reqs))

        for r in complex_reqs:
            self._tmp_extras_require[':' + str(r.marker)].append(r)
        self.extras_require = dict(
            (k, [str(r) for r in map(self._clean_req, v)])
            for k, v in self._tmp_extras_require.items()
        )

    def _clean_req(self, req):
        """
        Given a Requirement, remove environment markers and return it.
        """
        req.marker = None
        return req

    # FIXME: 'Distribution._parse_config_files' is too complex (14)
    def _parse_config_files(self, filenames=None):  # noqa: C901
        """
        Adapted from distutils.dist.Distribution.parse_config_files,
        this method provides the same functionality in subtly-improved
        ways.
        """
        from configparser import ConfigParser

        # Ignore install directory options if we have a venv
        ignore_options = [] if sys.prefix == sys.base_prefix else [
            'install-base', 'install-platbase', 'install-lib',
            'install-platlib', 'install-purelib', 'install-headers',
            'install-scripts', 'install-data', 'prefix', 'exec-prefix',
            'home', 'user', 'root',
        ]

        ignore_options = frozenset(ignore_options)

        if filenames is None:
            filenames = self.find_config_files()

        if DEBUG:
            self.announce("Distribution.parse_config_files():")

        parser = ConfigParser()
        for filename in filenames:
            with io.open(filename, encoding='utf-8') as reader:
                if DEBUG:
                    self.announce("  reading {filename}".format(**locals()))
                parser.read_file(reader)
            for section in parser.sections():
                options = parser.options(section)
                opt_dict = self.get_option_dict(section)

                for opt in options:
                    if opt == '__name__' or opt in ignore_options:
                        continue

                    val = parser.get(section, opt)
                    opt = opt.replace('-', '_')
                    opt_dict[opt] = (filename, val)

            # Make the ConfigParser forget everything (so we retain
            # the original filenames that options come from)
            parser.__init__()

        if 'global' not in self.command_options:
            return

        # If there was a "global" section in the config file, use it
        # to set Distribution options.

        for (opt, (src, val)) in self.command_options['global'].items():
            alias = self.negative_opt.get(opt)
            if alias:
                val = not strtobool(val)
            elif opt in ('verbose', 'dry_run'):  # ugh!
                val = strtobool(val)

            try:
                setattr(self, alias or opt, val)
            except ValueError as e:
                raise DistutilsOptionError(e) from e

    # FIXME: 'Distribution._set_command_options' is too complex (14)
    def _set_command_options(self, command_obj, option_dict=None):  # noqa: C901
        """
        Set the options for 'command_obj' from 'option_dict'.  Basically
        this means copying elements of a dictionary ('option_dict') to
        attributes of an instance ('command').

        'command_obj' must be a Command instance.  If 'option_dict' is not
        supplied, uses the standard option dictionary for this command
        (from 'self.command_options').

        (Adopted from distutils.dist.Distribution._set_command_options)
        """
        command_name = command_obj.get_command_name()
        if option_dict is None:
            option_dict = self.get_option_dict(command_name)

        if DEBUG:
            self.announce("  setting options for '%s' command:" % command_name)
        for (option, (source, value)) in option_dict.items():
            if DEBUG:
                self.announce("    %s = %s (from %s)" % (option, value,
                                                         source))
            try:
                bool_opts = [translate_longopt(o)
                             for o in command_obj.boolean_options]
            except AttributeError:
                bool_opts = []
            try:
                neg_opt = command_obj.negative_opt
            except AttributeError:
                neg_opt = {}

            try:
                is_string = isinstance(value, str)
                if option in neg_opt and is_string:
                    setattr(command_obj, neg_opt[option], not strtobool(value))
                elif option in bool_opts and is_string:
                    setattr(command_obj, option, strtobool(value))
                elif hasattr(command_obj, option):
                    setattr(command_obj, option, value)
                else:
                    raise DistutilsOptionError(
                        "error in %s: command '%s' has no such option '%s'"
                        % (source, command_name, option))
            except ValueError as e:
                raise DistutilsOptionError(e) from e

    def parse_config_files(self, filenames=None, ignore_option_errors=False):
        """Parses configuration files from various levels
        and loads configuration.

        """
        self._parse_config_files(filenames=filenames)

        parse_configuration(self, self.command_options,
                            ignore_option_errors=ignore_option_errors)
        self._finalize_requires()

    def fetch_build_eggs(self, requires):
        """Resolve pre-setup requirements"""
        resolved_dists = pkg_resources.working_set.resolve(
            pkg_resources.parse_requirements(requires),
            installer=self.fetch_build_egg,
            replace_conflicting=True,
        )
        for dist in resolved_dists:
            pkg_resources.working_set.add(dist, replace=True)
        return resolved_dists

    def finalize_options(self):
        """
        Allow plugins to apply arbitrary operations to the
        distribution. Each hook may optionally define a 'order'
        to influence the order of execution. Smaller numbers
        go first and the default is 0.
        """
        group = 'setuptools.finalize_distribution_options'

        def by_order(hook):
            return getattr(hook, 'order', 0)
        eps = map(lambda e: e.load(), pkg_resources.iter_entry_points(group))
        for ep in sorted(eps, key=by_order):
            ep(self)

    def _finalize_setup_keywords(self):
        for ep in pkg_resources.iter_entry_points('distutils.setup_keywords'):
            value = getattr(self, ep.name, None)
            if value is not None:
                ep.require(installer=self.fetch_build_egg)
                ep.load()(self, ep.name, value)

    def _finalize_2to3_doctests(self):
        if getattr(self, 'convert_2to3_doctests', None):
            # XXX may convert to set here when we can rely on set being builtin
            self.convert_2to3_doctests = [
                os.path.abspath(p)
                for p in self.convert_2to3_doctests
            ]
        else:
            self.convert_2to3_doctests = []

    def get_egg_cache_dir(self):
        egg_cache_dir = os.path.join(os.curdir, '.eggs')
        if not os.path.exists(egg_cache_dir):
            os.mkdir(egg_cache_dir)
            windows_support.hide_file(egg_cache_dir)
            readme_txt_filename = os.path.join(egg_cache_dir, 'README.txt')
            with open(readme_txt_filename, 'w') as f:
                f.write('This directory contains eggs that were downloaded '
                        'by setuptools to build, test, and run plug-ins.\n\n')
                f.write('This directory caches those eggs to prevent '
                        'repeated downloads.\n\n')
                f.write('However, it is safe to delete this directory.\n\n')

        return egg_cache_dir

    def fetch_build_egg(self, req):
        """Fetch an egg needed for building"""
        from setuptools.installer import fetch_build_egg
        return fetch_build_egg(self, req)

    def get_command_class(self, command):
        """Pluggable version of get_command_class()"""
        if command in self.cmdclass:
            return self.cmdclass[command]

        eps = pkg_resources.iter_entry_points('distutils.commands', command)
        for ep in eps:
            ep.require(installer=self.fetch_build_egg)
            self.cmdclass[command] = cmdclass = ep.load()
            return cmdclass
        else:
            return _Distribution.get_command_class(self, command)

    def print_commands(self):
        for ep in pkg_resources.iter_entry_points('distutils.commands'):
            if ep.name not in self.cmdclass:
                # don't require extras as the commands won't be invoked
                cmdclass = ep.resolve()
                self.cmdclass[ep.name] = cmdclass
        return _Distribution.print_commands(self)

    def get_command_list(self):
        for ep in pkg_resources.iter_entry_points('distutils.commands'):
            if ep.name not in self.cmdclass:
                # don't require extras as the commands won't be invoked
                cmdclass = ep.resolve()
                self.cmdclass[ep.name] = cmdclass
        return _Distribution.get_command_list(self)

    def include(self, **attrs):
        """Add items to distribution that are named in keyword arguments

        For example, 'dist.include(py_modules=["x"])' would add 'x' to
        the distribution's 'py_modules' attribute, if it was not already
        there.

        Currently, this method only supports inclusion for attributes that are
        lists or tuples.  If you need to add support for adding to other
        attributes in this or a subclass, you can add an '_include_X' method,
        where 'X' is the name of the attribute.  The method will be called with
        the value passed to 'include()'.  So, 'dist.include(foo={"bar":"baz"})'
        will try to call 'dist._include_foo({"bar":"baz"})', which can then
        handle whatever special inclusion logic is needed.
        """
        for k, v in attrs.items():
            include = getattr(self, '_include_' + k, None)
            if include:
                include(v)
            else:
                self._include_misc(k, v)

    def exclude_package(self, package):
        """Remove packages, modules, and extensions in named package"""

        pfx = package + '.'
        if self.packages:
            self.packages = [
                p for p in self.packages
                if p != package and not p.startswith(pfx)
            ]

        if self.py_modules:
            self.py_modules = [
                p for p in self.py_modules
                if p != package and not p.startswith(pfx)
            ]

        if self.ext_modules:
            self.ext_modules = [
                p for p in self.ext_modules
                if p.name != package and not p.name.startswith(pfx)
            ]

    def has_contents_for(self, package):
        """Return true if 'exclude_package(package)' would do something"""

        pfx = package + '.'

        for p in self.iter_distribution_names():
            if p == package or p.startswith(pfx):
                return True

    def _exclude_misc(self, name, value):
        """Handle 'exclude()' for list/tuple attrs without a special handler"""
        if not isinstance(value, sequence):
            raise DistutilsSetupError(
                "%s: setting must be a list or tuple (%r)" % (name, value)
            )
        try:
            old = getattr(self, name)
        except AttributeError as e:
            raise DistutilsSetupError(
                "%s: No such distribution setting" % name
            ) from e
        if old is not None and not isinstance(old, sequence):
            raise DistutilsSetupError(
                name + ": this setting cannot be changed via include/exclude"
            )
        elif old:
            setattr(self, name, [item for item in old if item not in value])

    def _include_misc(self, name, value):
        """Handle 'include()' for list/tuple attrs without a special handler"""

        if not isinstance(value, sequence):
            raise DistutilsSetupError(
                "%s: setting must be a list (%r)" % (name, value)
            )
        try:
            old = getattr(self, name)
        except AttributeError as e:
            raise DistutilsSetupError(
                "%s: No such distribution setting" % name
            ) from e
        if old is None:
            setattr(self, name, value)
        elif not isinstance(old, sequence):
            raise DistutilsSetupError(
                name + ": this setting cannot be changed via include/exclude"
            )
        else:
            new = [item for item in value if item not in old]
            setattr(self, name, old + new)

    def exclude(self, **attrs):
        """Remove items from distribution that are named in keyword arguments

        For example, 'dist.exclude(py_modules=["x"])' would remove 'x' from
        the distribution's 'py_modules' attribute.  Excluding packages uses
        the 'exclude_package()' method, so all of the package's contained
        packages, modules, and extensions are also excluded.

        Currently, this method only supports exclusion from attributes that are
        lists or tuples.  If you need to add support for excluding from other
        attributes in this or a subclass, you can add an '_exclude_X' method,
        where 'X' is the name of the attribute.  The method will be called with
        the value passed to 'exclude()'.  So, 'dist.exclude(foo={"bar":"baz"})'
        will try to call 'dist._exclude_foo({"bar":"baz"})', which can then
        handle whatever special exclusion logic is needed.
        """
        for k, v in attrs.items():
            exclude = getattr(self, '_exclude_' + k, None)
            if exclude:
                exclude(v)
            else:
                self._exclude_misc(k, v)

    def _exclude_packages(self, packages):
        if not isinstance(packages, sequence):
            raise DistutilsSetupError(
                "packages: setting must be a list or tuple (%r)" % (packages,)
            )
        list(map(self.exclude_package, packages))

    def _parse_command_opts(self, parser, args):
        # Remove --with-X/--without-X options when processing command args
        self.global_options = self.__class__.global_options
        self.negative_opt = self.__class__.negative_opt

        # First, expand any aliases
        command = args[0]
        aliases = self.get_option_dict('aliases')
        while command in aliases:
            src, alias = aliases[command]
            del aliases[command]  # ensure each alias can expand only once!
            import shlex
            args[:1] = shlex.split(alias, True)
            command = args[0]

        nargs = _Distribution._parse_command_opts(self, parser, args)

        # Handle commands that want to consume all remaining arguments
        cmd_class = self.get_command_class(command)
        if getattr(cmd_class, 'command_consumes_arguments', None):
            self.get_option_dict(command)['args'] = ("command line", nargs)
            if nargs is not None:
                return []

        return nargs

    def get_cmdline_options(self):
        """Return a '{cmd: {opt:val}}' map of all command-line options

        Option names are all long, but do not include the leading '--', and
        contain dashes rather than underscores.  If the option doesn't take
        an argument (e.g. '--quiet'), the 'val' is 'None'.

        Note that options provided by config files are intentionally excluded.
        """

        d = {}

        for cmd, opts in self.command_options.items():

            for opt, (src, val) in opts.items():

                if src != "command line":
                    continue

                opt = opt.replace('_', '-')

                if val == 0:
                    cmdobj = self.get_command_obj(cmd)
                    neg_opt = self.negative_opt.copy()
                    neg_opt.update(getattr(cmdobj, 'negative_opt', {}))
                    for neg, pos in neg_opt.items():
                        if pos == opt:
                            opt = neg
                            val = None
                            break
                    else:
                        raise AssertionError("Shouldn't be able to get here")

                elif val == 1:
                    val = None

                d.setdefault(cmd, {})[opt] = val

        return d

    def iter_distribution_names(self):
        """Yield all packages, modules, and extension names in distribution"""

        for pkg in self.packages or ():
            yield pkg

        for module in self.py_modules or ():
            yield module

        for ext in self.ext_modules or ():
            if isinstance(ext, tuple):
                name, buildinfo = ext
            else:
                name = ext.name
            if name.endswith('module'):
                name = name[:-6]
            yield name

    def handle_display_options(self, option_order):
        """If there were any non-global "display-only" options
        (--help-commands or the metadata display options) on the command
        line, display the requested info and return true; else return
        false.
        """
        import sys

        if self.help_commands:
            return _Distribution.handle_display_options(self, option_order)

        # Stdout may be StringIO (e.g. in tests)
        if not isinstance(sys.stdout, io.TextIOWrapper):
            return _Distribution.handle_display_options(self, option_order)

        # Don't wrap stdout if utf-8 is already the encoding. Provides
        #  workaround for #334.
        if sys.stdout.encoding.lower() in ('utf-8', 'utf8'):
            return _Distribution.handle_display_options(self, option_order)

        # Print metadata in UTF-8 no matter the platform
        encoding = sys.stdout.encoding
        errors = sys.stdout.errors
        newline = sys.platform != 'win32' and '\n' or None
        line_buffering = sys.stdout.line_buffering

        sys.stdout = io.TextIOWrapper(
            sys.stdout.detach(), 'utf-8', errors, newline, line_buffering)
        try:
            return _Distribution.handle_display_options(self, option_order)
        finally:
            sys.stdout = io.TextIOWrapper(
                sys.stdout.detach(), encoding, errors, newline, line_buffering)


class DistDeprecationWarning(SetuptoolsDeprecationWarning):
    """Class for warning about deprecations in dist in
    setuptools. Not ignored by default, unlike DeprecationWarning."""

setuptools/dist.py
# -*- coding: utf-8 -*-
__all__ = ['Distribution']

import io
import sys
import re
import os
import warnings
import numbers
import distutils.log
import distutils.core
import distutils.cmd
import distutils.dist
from distutils.util import strtobool
from distutils.debug import DEBUG
from distutils.fancy_getopt import translate_longopt
import itertools

from collections import defaultdict
from email import message_from_file

from distutils.errors import DistutilsOptionError, DistutilsSetupError
from distutils.util import rfc822_escape
from distutils.version import StrictVersion

from setuptools.extern import packaging
from setuptools.extern import ordered_set

from . import SetuptoolsDeprecationWarning

import setuptools
from setuptools import windows_support
from setuptools.monkey import get_unpatched
from setuptools.config import parse_configuration
import pkg_resources

__import__('setuptools.extern.packaging.specifiers')
__import__('setuptools.extern.packaging.version')


def _get_unpatched(cls):
    warnings.warn("Do not call this function", DistDeprecationWarning)
    return get_unpatched(cls)


def get_metadata_version(self):
    mv = getattr(self, 'metadata_version', None)

    if mv is None:
        if self.long_description_content_type or self.provides_extras:
            mv = StrictVersion('2.1')
        elif (self.maintainer is not None or
              self.maintainer_email is not None or
              getattr(self, 'python_requires', None) is not None or
              self.project_urls):
            mv = StrictVersion('1.2')
        elif (self.provides or self.requires or self.obsoletes or
                self.classifiers or self.download_url):
            mv = StrictVersion('1.1')
        else:
            mv = StrictVersion('1.0')

        self.metadata_version = mv

    return mv


def read_pkg_file(self, file):
    """Reads the metadata values from a file object."""
    msg = message_from_file(file)

    def _read_field(name):
        value = msg[name]
        if value == 'UNKNOWN':
            return None
        return value

    def _read_list(name):
        values = msg.get_all(name, None)
        if values == []:
            return None
        return values

    self.metadata_version = StrictVersion(msg['metadata-version'])
    self.name = _read_field('name')
    self.version = _read_field('version')
    self.description = _read_field('summary')
    # we are filling author only.
    self.author = _read_field('author')
    self.maintainer = None
    self.author_email = _read_field('author-email')
    self.maintainer_email = None
    self.url = _read_field('home-page')
    self.license = _read_field('license')

    if 'download-url' in msg:
        self.download_url = _read_field('download-url')
    else:
        self.download_url = None

    self.long_description = _read_field('description')
    self.description = _read_field('summary')

    if 'keywords' in msg:
        self.keywords = _read_field('keywords').split(',')

    self.platforms = _read_list('platform')
    self.classifiers = _read_list('classifier')

    # PEP 314 - these fields only exist in 1.1
    if self.metadata_version == StrictVersion('1.1'):
        self.requires = _read_list('requires')
        self.provides = _read_list('provides')
        self.obsoletes = _read_list('obsoletes')
    else:
        self.requires = None
        self.provides = None
        self.obsoletes = None


def single_line(val):
    # quick and dirty validation for description pypa/setuptools#1390
    if '\n' in val:
        # TODO after 2021-07-31: Replace with `raise ValueError("newlines not allowed")`
        warnings.UserWarning("newlines not allowed and will break in the future")
        val = val.replace('\n', ' ')
    return val


# Based on Python 3.5 version
def write_pkg_file(self, file):  # noqa: C901  # is too complex (14)  # FIXME
    """Write the PKG-INFO format data to a file object.
    """
    version = self.get_metadata_version()

    def write_field(key, value):
        file.write("%s: %s\n" % (key, value))

    write_field('Metadata-Version', str(version))
    write_field('Name', self.get_name())
    write_field('Version', self.get_version())
    write_field('Summary', single_line(self.get_description()))
    write_field('Home-page', self.get_url())

    if version < StrictVersion('1.2'):
        write_field('Author', self.get_contact())
        write_field('Author-email', self.get_contact_email())
    else:
        optional_fields = (
            ('Author', 'author'),
            ('Author-email', 'author_email'),
            ('Maintainer', 'maintainer'),
            ('Maintainer-email', 'maintainer_email'),
        )

        for field, attr in optional_fields:
            attr_val = getattr(self, attr)

            if attr_val is not None:
                write_field(field, attr_val)

    write_field('License', self.get_license())
    if self.download_url:
        write_field('Download-URL', self.download_url)
    for project_url in self.project_urls.items():
        write_field('Project-URL', '%s, %s' % project_url)

    long_desc = rfc822_escape(self.get_long_description())
    write_field('Description', long_desc)

    keywords = ','.join(self.get_keywords())
    if keywords:
        write_field('Keywords', keywords)

    if version >= StrictVersion('1.2'):
        for platform in self.get_platforms():
            write_field('Platform', platform)
    else:
        self._write_list(file, 'Platform', self.get_platforms())

    self._write_list(file, 'Classifier', self.get_classifiers())

    # PEP 314
    self._write_list(file, 'Requires', self.get_requires())
    self._write_list(file, 'Provides', self.get_provides())
    self._write_list(file, 'Obsoletes', self.get_obsoletes())

    # Setuptools specific for PEP 345
    if hasattr(self, 'python_requires'):
        write_field('Requires-Python', self.python_requires)

    # PEP 566
    if self.long_description_content_type:
        write_field(
            'Description-Content-Type',
            self.long_description_content_type
        )
    if self.provides_extras:
        for extra in self.provides_extras:
            write_field('Provides-Extra', extra)


sequence = tuple, list


def check_importable(dist, attr, value):
    try:
        ep = pkg_resources.EntryPoint.parse('x=' + value)
        assert not ep.extras
    except (TypeError, ValueError, AttributeError, AssertionError) as e:
        raise DistutilsSetupError(
            "%r must be importable 'module:attrs' string (got %r)"
            % (attr, value)
        ) from e


def assert_string_list(dist, attr, value):
    """Verify that value is a string list"""
    try:
        # verify that value is a list or tuple to exclude unordered
        # or single-use iterables
        assert isinstance(value, (list, tuple))
        # verify that elements of value are strings
        assert ''.join(value) != value
    except (TypeError, ValueError, AttributeError, AssertionError) as e:
        raise DistutilsSetupError(
            "%r must be a list of strings (got %r)" % (attr, value)
        ) from e


def check_nsp(dist, attr, value):
    """Verify that namespace packages are valid"""
    ns_packages = value
    assert_string_list(dist, attr, ns_packages)
    for nsp in ns_packages:
        if not dist.has_contents_for(nsp):
            raise DistutilsSetupError(
                "Distribution contains no modules or packages for " +
                "namespace package %r" % nsp
            )
        parent, sep, child = nsp.rpartition('.')
        if parent and parent not in ns_packages:
            distutils.log.warn(
                "WARNING: %r is declared as a package namespace, but %r"
                " is not: please correct this in setup.py", nsp, parent
            )


def check_extras(dist, attr, value):
    """Verify that extras_require mapping is valid"""
    try:
        list(itertools.starmap(_check_extra, value.items()))
    except (TypeError, ValueError, AttributeError) as e:
        raise DistutilsSetupError(
            "'extras_require' must be a dictionary whose values are "
            "strings or lists of strings containing valid project/version "
            "requirement specifiers."
        ) from e


def _check_extra(extra, reqs):
    name, sep, marker = extra.partition(':')
    if marker and pkg_resources.invalid_marker(marker):
        raise DistutilsSetupError("Invalid environment marker: " + marker)
    list(pkg_resources.parse_requirements(reqs))


def assert_bool(dist, attr, value):
    """Verify that value is True, False, 0, or 1"""
    if bool(value) != value:
        tmpl = "{attr!r} must be a boolean value (got {value!r})"
        raise DistutilsSetupError(tmpl.format(attr=attr, value=value))


def check_requirements(dist, attr, value):
    """Verify that install_requires is a valid requirements list"""
    try:
        list(pkg_resources.parse_requirements(value))
        if isinstance(value, (dict, set)):
            raise TypeError("Unordered types are not allowed")
    except (TypeError, ValueError) as error:
        tmpl = (
            "{attr!r} must be a string or list of strings "
            "containing valid project/version requirement specifiers; {error}"
        )
        raise DistutilsSetupError(
            tmpl.format(attr=attr, error=error)
        ) from error


def check_specifier(dist, attr, value):
    """Verify that value is a valid version specifier"""
    try:
        packaging.specifiers.SpecifierSet(value)
    except packaging.specifiers.InvalidSpecifier as error:
        tmpl = (
            "{attr!r} must be a string "
            "containing valid version specifiers; {error}"
        )
        raise DistutilsSetupError(
            tmpl.format(attr=attr, error=error)
        ) from error


def check_entry_points(dist, attr, value):
    """Verify that entry_points map is parseable"""
    try:
        pkg_resources.EntryPoint.parse_map(value)
    except ValueError as e:
        raise DistutilsSetupError(e) from e


def check_test_suite(dist, attr, value):
    if not isinstance(value, str):
        raise DistutilsSetupError("test_suite must be a string")


def check_package_data(dist, attr, value):
    """Verify that value is a dictionary of package names to glob lists"""
    if not isinstance(value, dict):
        raise DistutilsSetupError(
            "{!r} must be a dictionary mapping package names to lists of "
            "string wildcard patterns".format(attr))
    for k, v in value.items():
        if not isinstance(k, str):
            raise DistutilsSetupError(
                "keys of {!r} dict must be strings (got {!r})"
                .format(attr, k)
            )
        assert_string_list(dist, 'values of {!r} dict'.format(attr), v)


def check_packages(dist, attr, value):
    for pkgname in value:
        if not re.match(r'\w+(\.\w+)*', pkgname):
            distutils.log.warn(
                "WARNING: %r not a valid package name; please use only "
                ".-separated package names in setup.py", pkgname
            )


_Distribution = get_unpatched(distutils.core.Distribution)


class Distribution(_Distribution):
    """Distribution with support for tests and package data

    This is an enhanced version of 'distutils.dist.Distribution' that
    effectively adds the following new optional keyword arguments to 'setup()':

     'install_requires' -- a string or sequence of strings specifying project
        versions that the distribution requires when installed, in the format
        used by 'pkg_resources.require()'.  They will be installed
        automatically when the package is installed.  If you wish to use
        packages that are not available in PyPI, or want to give your users an
        alternate download location, you can add a 'find_links' option to the
        '[easy_install]' section of your project's 'setup.cfg' file, and then
        setuptools will scan the listed web pages for links that satisfy the
        requirements.

     'extras_require' -- a dictionary mapping names of optional "extras" to the
        additional requirement(s) that using those extras incurs. For example,
        this::

            extras_require = dict(reST = ["docutils>=0.3", "reSTedit"])

        indicates that the distribution can optionally provide an extra
        capability called "reST", but it can only be used if docutils and
        reSTedit are installed.  If the user installs your package using
        EasyInstall and requests one of your extras, the corresponding
        additional requirements will be installed if needed.

     'test_suite' -- the name of a test suite to run for the 'test' command.
        If the user runs 'python setup.py test', the package will be installed,
        and the named test suite will be run.  The format is the same as
        would be used on a 'unittest.py' command line.  That is, it is the
        dotted name of an object to import and call to generate a test suite.

     'package_data' -- a dictionary mapping package names to lists of filenames
        or globs to use to find data files contained in the named packages.
        If the dictionary has filenames or globs listed under '""' (the empty
        string), those names will be searched for in every package, in addition
        to any names for the specific package.  Data files found using these
        names/globs will be installed along with the package, in the same
        location as the package.  Note that globs are allowed to reference
        the contents of non-package subdirectories, as long as you use '/' as
        a path separator.  (Globs are automatically converted to
        platform-specific paths at runtime.)

    In addition to these new keywords, this class also has several new methods
    for manipulating the distribution's contents.  For example, the 'include()'
    and 'exclude()' methods can be thought of as in-place add and subtract
    commands that add or remove packages, modules, extensions, and so on from
    the distribution.
    """

    _DISTUTILS_UNSUPPORTED_METADATA = {
        'long_description_content_type': None,
        'project_urls': dict,
        'provides_extras': ordered_set.OrderedSet,
        'license_files': ordered_set.OrderedSet,
    }

    _patched_dist = None

    def patch_missing_pkg_info(self, attrs):
        # Fake up a replacement for the data that would normally come from
        # PKG-INFO, but which might not yet be built if this is a fresh
        # checkout.
        #
        if not attrs or 'name' not in attrs or 'version' not in attrs:
            return
        key = pkg_resources.safe_name(str(attrs['name'])).lower()
        dist = pkg_resources.working_set.by_key.get(key)
        if dist is not None and not dist.has_metadata('PKG-INFO'):
            dist._version = pkg_resources.safe_version(str(attrs['version']))
            self._patched_dist = dist

    def __init__(self, attrs=None):
        have_package_data = hasattr(self, "package_data")
        if not have_package_data:
            self.package_data = {}
        attrs = attrs or {}
        self.dist_files = []
        # Filter-out setuptools' specific options.
        self.src_root = attrs.pop("src_root", None)
        self.patch_missing_pkg_info(attrs)
        self.dependency_links = attrs.pop('dependency_links', [])
        self.setup_requires = attrs.pop('setup_requires', [])
        for ep in pkg_resources.iter_entry_points('distutils.setup_keywords'):
            vars(self).setdefault(ep.name, None)
        _Distribution.__init__(self, {
            k: v for k, v in attrs.items()
            if k not in self._DISTUTILS_UNSUPPORTED_METADATA
        })

        # Fill-in missing metadata fields not supported by distutils.
        # Note some fields may have been set by other tools (e.g. pbr)
        # above; they are taken preferrentially to setup() arguments
        for option, default in self._DISTUTILS_UNSUPPORTED_METADATA.items():
            for source in self.metadata.__dict__, attrs:
                if option in source:
                    value = source[option]
                    break
            else:
                value = default() if default else None
            setattr(self.metadata, option, value)

        self.metadata.version = self._normalize_version(
            self._validate_version(self.metadata.version))
        self._finalize_requires()

    @staticmethod
    def _normalize_version(version):
        if isinstance(version, setuptools.sic) or version is None:
            return version

        normalized = str(packaging.version.Version(version))
        if version != normalized:
            tmpl = "Normalizing '{version}' to '{normalized}'"
            warnings.warn(tmpl.format(**locals()))
            return normalized
        return version

    @staticmethod
    def _validate_version(version):
        if isinstance(version, numbers.Number):
            # Some people apparently take "version number" too literally :)
            version = str(version)

        if version is not None:
            try:
                packaging.version.Version(version)
            except (packaging.version.InvalidVersion, TypeError):
                warnings.warn(
                    "The version specified (%r) is an invalid version, this "
                    "may not work as expected with newer versions of "
                    "setuptools, pip, and PyPI. Please see PEP 440 for more "
                    "details." % version
                )
                return setuptools.sic(version)
        return version

    def _finalize_requires(self):
        """
        Set `metadata.python_requires` and fix environment markers
        in `install_requires` and `extras_require`.
        """
        if getattr(self, 'python_requires', None):
            self.metadata.python_requires = self.python_requires

        if getattr(self, 'extras_require', None):
            for extra in self.extras_require.keys():
                # Since this gets called multiple times at points where the
                # keys have become 'converted' extras, ensure that we are only
                # truly adding extras we haven't seen before here.
                extra = extra.split(':')[0]
                if extra:
                    self.metadata.provides_extras.add(extra)

        self._convert_extras_requirements()
        self._move_install_requirements_markers()

    def _convert_extras_requirements(self):
        """
        Convert requirements in `extras_require` of the form
        `"extra": ["barbazquux; {marker}"]` to
        `"extra:{marker}": ["barbazquux"]`.
        """
        spec_ext_reqs = getattr(self, 'extras_require', None) or {}
        self._tmp_extras_require = defaultdict(list)
        for section, v in spec_ext_reqs.items():
            # Do not strip empty sections.
            self._tmp_extras_require[section]
            for r in pkg_resources.parse_requirements(v):
                suffix = self._suffix_for(r)
                self._tmp_extras_require[section + suffix].append(r)

    @staticmethod
    def _suffix_for(req):
        """
        For a requirement, return the 'extras_require' suffix for
        that requirement.
        """
        return ':' + str(req.marker) if req.marker else ''

    def _move_install_requirements_markers(self):
        """
        Move requirements in `install_requires` that are using environment
        markers `extras_require`.
        """

        # divide the install_requires into two sets, simple ones still
        # handled by install_requires and more complex ones handled
        # by extras_require.

        def is_simple_req(req):
            return not req.marker

        spec_inst_reqs = getattr(self, 'install_requires', None) or ()
        inst_reqs = list(pkg_resources.parse_requirements(spec_inst_reqs))
        simple_reqs = filter(is_simple_req, inst_reqs)
        complex_reqs = itertools.filterfalse(is_simple_req, inst_reqs)
        self.install_requires = list(map(str, simple_reqs))

        for r in complex_reqs:
            self._tmp_extras_require[':' + str(r.marker)].append(r)
        self.extras_require = dict(
            (k, [str(r) for r in map(self._clean_req, v)])
            for k, v in self._tmp_extras_require.items()
        )

    def _clean_req(self, req):
        """
        Given a Requirement, remove environment markers and return it.
        """
        req.marker = None
        return req

    # FIXME: 'Distribution._parse_config_files' is too complex (14)
    def _parse_config_files(self, filenames=None):  # noqa: C901
        """
        Adapted from distutils.dist.Distribution.parse_config_files,
        this method provides the same functionality in subtly-improved
        ways.
        """
        from configparser import ConfigParser

        # Ignore install directory options if we have a venv
        ignore_options = [] if sys.prefix == sys.base_prefix else [
            'install-base', 'install-platbase', 'install-lib',
            'install-platlib', 'install-purelib', 'install-headers',
            'install-scripts', 'install-data', 'prefix', 'exec-prefix',
            'home', 'user', 'root',
        ]

        ignore_options = frozenset(ignore_options)

        if filenames is None:
            filenames = self.find_config_files()

        if DEBUG:
            self.announce("Distribution.parse_config_files():")

        parser = ConfigParser()
        for filename in filenames:
            with io.open(filename, encoding='utf-8') as reader:
                if DEBUG:
                    self.announce("  reading {filename}".format(**locals()))
                parser.read_file(reader)
            for section in parser.sections():
                options = parser.options(section)
                opt_dict = self.get_option_dict(section)

                for opt in options:
                    if opt == '__name__' or opt in ignore_options:
                        continue

                    val = parser.get(section, opt)
                    opt = opt.replace('-', '_')
                    opt_dict[opt] = (filename, val)

            # Make the ConfigParser forget everything (so we retain
            # the original filenames that options come from)
            parser.__init__()

        if 'global' not in self.command_options:
            return

        # If there was a "global" section in the config file, use it
        # to set Distribution options.

        for (opt, (src, val)) in self.command_options['global'].items():
            alias = self.negative_opt.get(opt)
            if alias:
                val = not strtobool(val)
            elif opt in ('verbose', 'dry_run'):  # ugh!
                val = strtobool(val)

            try:
                setattr(self, alias or opt, val)
            except ValueError as e:
                raise DistutilsOptionError(e) from e

    # FIXME: 'Distribution._set_command_options' is too complex (14)
    def _set_command_options(self, command_obj, option_dict=None):  # noqa: C901
        """
        Set the options for 'command_obj' from 'option_dict'.  Basically
        this means copying elements of a dictionary ('option_dict') to
        attributes of an instance ('command').

        'command_obj' must be a Command instance.  If 'option_dict' is not
        supplied, uses the standard option dictionary for this command
        (from 'self.command_options').

        (Adopted from distutils.dist.Distribution._set_command_options)
        """
        command_name = command_obj.get_command_name()
        if option_dict is None:
            option_dict = self.get_option_dict(command_name)

        if DEBUG:
            self.announce("  setting options for '%s' command:" % command_name)
        for (option, (source, value)) in option_dict.items():
            if DEBUG:
                self.announce("    %s = %s (from %s)" % (option, value,
                                                         source))
            try:
                bool_opts = [translate_longopt(o)
                             for o in command_obj.boolean_options]
            except AttributeError:
                bool_opts = []
            try:
                neg_opt = command_obj.negative_opt
            except AttributeError:
                neg_opt = {}

            try:
                is_string = isinstance(value, str)
                if option in neg_opt and is_string:
                    setattr(command_obj, neg_opt[option], not strtobool(value))
                elif option in bool_opts and is_string:
                    setattr(command_obj, option, strtobool(value))
                elif hasattr(command_obj, option):
                    setattr(command_obj, option, value)
                else:
                    raise DistutilsOptionError(
                        "error in %s: command '%s' has no such option '%s'"
                        % (source, command_name, option))
            except ValueError as e:
                raise DistutilsOptionError(e) from e

    def parse_config_files(self, filenames=None, ignore_option_errors=False):
        """Parses configuration files from various levels
        and loads configuration.

        """
        self._parse_config_files(filenames=filenames)

        parse_configuration(self, self.command_options,
                            ignore_option_errors=ignore_option_errors)
        self._finalize_requires()

    def fetch_build_eggs(self, requires):
        """Resolve pre-setup requirements"""
        resolved_dists = pkg_resources.working_set.resolve(
            pkg_resources.parse_requirements(requires),
            installer=self.fetch_build_egg,
            replace_conflicting=True,
        )
        for dist in resolved_dists:
            pkg_resources.working_set.add(dist, replace=True)
        return resolved_dists

    def finalize_options(self):
        """
        Allow plugins to apply arbitrary operations to the
        distribution. Each hook may optionally define a 'order'
        to influence the order of execution. Smaller numbers
        go first and the default is 0.
        """
        group = 'setuptools.finalize_distribution_options'

        def by_order(hook):
            return getattr(hook, 'order', 0)
        eps = map(lambda e: e.load(), pkg_resources.iter_entry_points(group))
        for ep in sorted(eps, key=by_order):
            ep(self)

    def _finalize_setup_keywords(self):
        for ep in pkg_resources.iter_entry_points('distutils.setup_keywords'):
            value = getattr(self, ep.name, None)
            if value is not None:
                ep.require(installer=self.fetch_build_egg)
                ep.load()(self, ep.name, value)

    def _finalize_2to3_doctests(self):
        if getattr(self, 'convert_2to3_doctests', None):
            # XXX may convert to set here when we can rely on set being builtin
            self.convert_2to3_doctests = [
                os.path.abspath(p)
                for p in self.convert_2to3_doctests
            ]
        else:
            self.convert_2to3_doctests = []

    def get_egg_cache_dir(self):
        egg_cache_dir = os.path.join(os.curdir, '.eggs')
        if not os.path.exists(egg_cache_dir):
            os.mkdir(egg_cache_dir)
            windows_support.hide_file(egg_cache_dir)
            readme_txt_filename = os.path.join(egg_cache_dir, 'README.txt')
            with open(readme_txt_filename, 'w') as f:
                f.write('This directory contains eggs that were downloaded '
                        'by setuptools to build, test, and run plug-ins.\n\n')
                f.write('This directory caches those eggs to prevent '
                        'repeated downloads.\n\n')
                f.write('However, it is safe to delete this directory.\n\n')

        return egg_cache_dir

    def fetch_build_egg(self, req):
        """Fetch an egg needed for building"""
        from setuptools.installer import fetch_build_egg
        return fetch_build_egg(self, req)

    def get_command_class(self, command):
        """Pluggable version of get_command_class()"""
        if command in self.cmdclass:
            return self.cmdclass[command]

        eps = pkg_resources.iter_entry_points('distutils.commands', command)
        for ep in eps:
            ep.require(installer=self.fetch_build_egg)
            self.cmdclass[command] = cmdclass = ep.load()
            return cmdclass
        else:
            return _Distribution.get_command_class(self, command)

    def print_commands(self):
        for ep in pkg_resources.iter_entry_points('distutils.commands'):
            if ep.name not in self.cmdclass:
                # don't require extras as the commands won't be invoked
                cmdclass = ep.resolve()
                self.cmdclass[ep.name] = cmdclass
        return _Distribution.print_commands(self)

    def get_command_list(self):
        for ep in pkg_resources.iter_entry_points('distutils.commands'):
            if ep.name not in self.cmdclass:
                # don't require extras as the commands won't be invoked
                cmdclass = ep.resolve()
                self.cmdclass[ep.name] = cmdclass
        return _Distribution.get_command_list(self)

    def include(self, **attrs):
        """Add items to distribution that are named in keyword arguments

        For example, 'dist.include(py_modules=["x"])' would add 'x' to
        the distribution's 'py_modules' attribute, if it was not already
        there.

        Currently, this method only supports inclusion for attributes that are
        lists or tuples.  If you need to add support for adding to other
        attributes in this or a subclass, you can add an '_include_X' method,
        where 'X' is the name of the attribute.  The method will be called with
        the value passed to 'include()'.  So, 'dist.include(foo={"bar":"baz"})'
        will try to call 'dist._include_foo({"bar":"baz"})', which can then
        handle whatever special inclusion logic is needed.
        """
        for k, v in attrs.items():
            include = getattr(self, '_include_' + k, None)
            if include:
                include(v)
            else:
                self._include_misc(k, v)

    def exclude_package(self, package):
        """Remove packages, modules, and extensions in named package"""

        pfx = package + '.'
        if self.packages:
            self.packages = [
                p for p in self.packages
                if p != package and not p.startswith(pfx)
            ]

        if self.py_modules:
            self.py_modules = [
                p for p in self.py_modules
                if p != package and not p.startswith(pfx)
            ]

        if self.ext_modules:
            self.ext_modules = [
                p for p in self.ext_modules
                if p.name != package and not p.name.startswith(pfx)
            ]

    def has_contents_for(self, package):
        """Return true if 'exclude_package(package)' would do something"""

        pfx = package + '.'

        for p in self.iter_distribution_names():
            if p == package or p.startswith(pfx):
                return True

    def _exclude_misc(self, name, value):
        """Handle 'exclude()' for list/tuple attrs without a special handler"""
        if not isinstance(value, sequence):
            raise DistutilsSetupError(
                "%s: setting must be a list or tuple (%r)" % (name, value)
            )
        try:
            old = getattr(self, name)
        except AttributeError as e:
            raise DistutilsSetupError(
                "%s: No such distribution setting" % name
            ) from e
        if old is not None and not isinstance(old, sequence):
            raise DistutilsSetupError(
                name + ": this setting cannot be changed via include/exclude"
            )
        elif old:
            setattr(self, name, [item for item in old if item not in value])

    def _include_misc(self, name, value):
        """Handle 'include()' for list/tuple attrs without a special handler"""

        if not isinstance(value, sequence):
            raise DistutilsSetupError(
                "%s: setting must be a list (%r)" % (name, value)
            )
        try:
            old = getattr(self, name)
        except AttributeError as e:
            raise DistutilsSetupError(
                "%s: No such distribution setting" % name
            ) from e
        if old is None:
            setattr(self, name, value)
        elif not isinstance(old, sequence):
            raise DistutilsSetupError(
                name + ": this setting cannot be changed via include/exclude"
            )
        else:
            new = [item for item in value if item not in old]
            setattr(self, name, old + new)

    def exclude(self, **attrs):
        """Remove items from distribution that are named in keyword arguments

        For example, 'dist.exclude(py_modules=["x"])' would remove 'x' from
        the distribution's 'py_modules' attribute.  Excluding packages uses
        the 'exclude_package()' method, so all of the package's contained
        packages, modules, and extensions are also excluded.

        Currently, this method only supports exclusion from attributes that are
        lists or tuples.  If you need to add support for excluding from other
        attributes in this or a subclass, you can add an '_exclude_X' method,
        where 'X' is the name of the attribute.  The method will be called with
        the value passed to 'exclude()'.  So, 'dist.exclude(foo={"bar":"baz"})'
        will try to call 'dist._exclude_foo({"bar":"baz"})', which can then
        handle whatever special exclusion logic is needed.
        """
        for k, v in attrs.items():
            exclude = getattr(self, '_exclude_' + k, None)
            if exclude:
                exclude(v)
            else:
                self._exclude_misc(k, v)

    def _exclude_packages(self, packages):
        if not isinstance(packages, sequence):
            raise DistutilsSetupError(
                "packages: setting must be a list or tuple (%r)" % (packages,)
            )
        list(map(self.exclude_package, packages))

    def _parse_command_opts(self, parser, args):
        # Remove --with-X/--without-X options when processing command args
        self.global_options = self.__class__.global_options
        self.negative_opt = self.__class__.negative_opt

        # First, expand any aliases
        command = args[0]
        aliases = self.get_option_dict('aliases')
        while command in aliases:
            src, alias = aliases[command]
            del aliases[command]  # ensure each alias can expand only once!
            import shlex
            args[:1] = shlex.split(alias, True)
            command = args[0]

        nargs = _Distribution._parse_command_opts(self, parser, args)

        # Handle commands that want to consume all remaining arguments
        cmd_class = self.get_command_class(command)
        if getattr(cmd_class, 'command_consumes_arguments', None):
            self.get_option_dict(command)['args'] = ("command line", nargs)
            if nargs is not None:
                return []

        return nargs

    def get_cmdline_options(self):
        """Return a '{cmd: {opt:val}}' map of all command-line options

        Option names are all long, but do not include the leading '--', and
        contain dashes rather than underscores.  If the option doesn't take
        an argument (e.g. '--quiet'), the 'val' is 'None'.

        Note that options provided by config files are intentionally excluded.
        """

        d = {}

        for cmd, opts in self.command_options.items():

            for opt, (src, val) in opts.items():

                if src != "command line":
                    continue

                opt = opt.replace('_', '-')

                if val == 0:
                    cmdobj = self.get_command_obj(cmd)
                    neg_opt = self.negative_opt.copy()
                    neg_opt.update(getattr(cmdobj, 'negative_opt', {}))
                    for neg, pos in neg_opt.items():
                        if pos == opt:
                            opt = neg
                            val = None
                            break
                    else:
                        raise AssertionError("Shouldn't be able to get here")

                elif val == 1:
                    val = None

                d.setdefault(cmd, {})[opt] = val

        return d

    def iter_distribution_names(self):
        """Yield all packages, modules, and extension names in distribution"""

        for pkg in self.packages or ():
            yield pkg

        for module in self.py_modules or ():
            yield module

        for ext in self.ext_modules or ():
            if isinstance(ext, tuple):
                name, buildinfo = ext
            else:
                name = ext.name
            if name.endswith('module'):
                name = name[:-6]
            yield name

    def handle_display_options(self, option_order):
        """If there were any non-global "display-only" options
        (--help-commands or the metadata display options) on the command
        line, display the requested info and return true; else return
        false.
        """
        import sys

        if self.help_commands:
            return _Distribution.handle_display_options(self, option_order)

        # Stdout may be StringIO (e.g. in tests)
        if not isinstance(sys.stdout, io.TextIOWrapper):
            return _Distribution.handle_display_options(self, option_order)

        # Don't wrap stdout if utf-8 is already the encoding. Provides
        #  workaround for #334.
        if sys.stdout.encoding.lower() in ('utf-8', 'utf8'):
            return _Distribution.handle_display_options(self, option_order)

        # Print metadata in UTF-8 no matter the platform
        encoding = sys.stdout.encoding
        errors = sys.stdout.errors
        newline = sys.platform != 'win32' and '\n' or None
        line_buffering = sys.stdout.line_buffering

        sys.stdout = io.TextIOWrapper(
            sys.stdout.detach(), 'utf-8', errors, newline, line_buffering)
        try:
            return _Distribution.handle_display_options(self, option_order)
        finally:
            sys.stdout = io.TextIOWrapper(
                sys.stdout.detach(), encoding, errors, newline, line_buffering)


class DistDeprecationWarning(SetuptoolsDeprecationWarning):
    """Class for warning about deprecations in dist in
    setuptools. Not ignored by default, unlike DeprecationWarning."""

setuptools/dist.py
diff --git a/changelog.d/1390.misc.rst b/changelog.d/1390.misc.rst
new file mode 100644
index 0000000000..5e4fb11488
--- /dev/null
+++ b/changelog.d/1390.misc.rst
@@ -0,0 +1 @@
+Validation of Description field now is more lenient, emitting a warning and mangling the value to be valid (replacing newlines with spaces).
diff --git a/setuptools/dist.py b/setuptools/dist.py
index 2d0aac333d..172d66b1f4 100644
--- a/setuptools/dist.py
+++ b/setuptools/dist.py
@@ -121,7 +121,9 @@ def _read_list(name):
 def single_line(val):
     # quick and dirty validation for description pypa/setuptools#1390
     if '\n' in val:
-        raise ValueError("newlines not allowed")
+        # TODO after 2021-07-31: Replace with `raise ValueError("newlines not allowed")`
+        warnings.UserWarning("newlines not allowed and will break in the future")
+        val = val.replace('\n', ' ')
     return val
 
 

Newlines in the `description` field produce a malformed PKG-INFO
We discovered this accidentally by way of https://github.com/zopefoundation/zc.relation/issues/4#issuecomment-397532224: if you pass a string containing newlines to the `description` argument of `setup()`, setuptools will generate a malformed PKG-INFO.

To reproduce:

```
# setup.py
from setuptools import setup
setup(
    name='test-package',
    version='0.1',
    author='Blah Blah',
    author_email='blah@example.com',
    description='description\n\n',
    py_modules=['blah'],
)
```
(The contents of `blah.py` do not matter, but the file should exist.)

Run `python setup.py sdist` and the inspect `test_package.egg-info/PKG-INFO`.  For me, with setuptools 39.1.0, it looks like this:

```
Metadata-Version: 1.0
Name: test-package
Version: 0.1
Summary: description


Home-page: UNKNOWN
Author: Blah Blah
Author-email: blah@example.com
License: UNKNOWN
Description: UNKNOWN
Platform: UNKNOWN
```

The extra newlines lead tools to treat the rest of the PKG-INFO as a long_description.

I would expect `setuptools` to complain about the newlines in the `description` field, or at least escape them properly (i.e. prepend whitespace, like it does for the `long_description` field).
