<h2>Editing File: /lib/python3.8/site-packages/pkg_resources/_vendor/packaging/markers.py</h2><form method='post'><textarea name='content' class='file-edit'># This file is dual licensed under the terms of the Apache License, Version
# 2.0, and the BSD License. See the LICENSE file in the root of this repository
# for complete details.
from __future__ import absolute_import, division, print_function

import operator
import os
import platform
import sys

from pkg_resources.extern.pyparsing import ParseException, ParseResults, stringStart, stringEnd
from pkg_resources.extern.pyparsing import ZeroOrMore, Group, Forward, QuotedString
from pkg_resources.extern.pyparsing import Literal as L  # noqa

from ._compat import string_types
from .specifiers import Specifier, InvalidSpecifier


__all__ = [
    &quot;InvalidMarker&quot;, &quot;UndefinedComparison&quot;, &quot;UndefinedEnvironmentName&quot;,
    &quot;Marker&quot;, &quot;default_environment&quot;,
]


class InvalidMarker(ValueError):
    &quot;&quot;&quot;
    An invalid marker was found, users should refer to PEP 508.
    &quot;&quot;&quot;


class UndefinedComparison(ValueError):
    &quot;&quot;&quot;
    An invalid operation was attempted on a value that doesn't support it.
    &quot;&quot;&quot;


class UndefinedEnvironmentName(ValueError):
    &quot;&quot;&quot;
    A name was attempted to be used that does not exist inside of the
    environment.
    &quot;&quot;&quot;


class Node(object):

    def __init__(self, value):
        self.value = value

    def __str__(self):
        return str(self.value)

    def __repr__(self):
        return &quot;&lt;{0}({1!r})&gt;&quot;.format(self.__class__.__name__, str(self))

    def serialize(self):
        raise NotImplementedError


class Variable(Node):

    def serialize(self):
        return str(self)


class Value(Node):

    def serialize(self):
        return '&quot;{0}&quot;'.format(self)


class Op(Node):

    def serialize(self):
        return str(self)


VARIABLE = (
    L(&quot;implementation_version&quot;) |
    L(&quot;platform_python_implementation&quot;) |
    L(&quot;implementation_name&quot;) |
    L(&quot;python_full_version&quot;) |
    L(&quot;platform_release&quot;) |
    L(&quot;platform_version&quot;) |
    L(&quot;platform_machine&quot;) |
    L(&quot;platform_system&quot;) |
    L(&quot;python_version&quot;) |
    L(&quot;sys_platform&quot;) |
    L(&quot;os_name&quot;) |
    L(&quot;os.name&quot;) |  # PEP-345
    L(&quot;sys.platform&quot;) |  # PEP-345
    L(&quot;platform.version&quot;) |  # PEP-345
    L(&quot;platform.machine&quot;) |  # PEP-345
    L(&quot;platform.python_implementation&quot;) |  # PEP-345
    L(&quot;python_implementation&quot;) |  # undocumented setuptools legacy
    L(&quot;extra&quot;)
)
ALIASES = {
    'os.name': 'os_name',
    'sys.platform': 'sys_platform',
    'platform.version': 'platform_version',
    'platform.machine': 'platform_machine',
    'platform.python_implementation': 'platform_python_implementation',
    'python_implementation': 'platform_python_implementation'
}
VARIABLE.setParseAction(lambda s, l, t: Variable(ALIASES.get(t[0], t[0])))

VERSION_CMP = (
    L(&quot;===&quot;) |
    L(&quot;==&quot;) |
    L(&quot;&gt;=&quot;) |
    L(&quot;&lt;=&quot;) |
    L(&quot;!=&quot;) |
    L(&quot;~=&quot;) |
    L(&quot;&gt;&quot;) |
    L(&quot;&lt;&quot;)
)

MARKER_OP = VERSION_CMP | L(&quot;not in&quot;) | L(&quot;in&quot;)
MARKER_OP.setParseAction(lambda s, l, t: Op(t[0]))

MARKER_VALUE = QuotedString(&quot;'&quot;) | QuotedString('&quot;')
MARKER_VALUE.setParseAction(lambda s, l, t: Value(t[0]))

BOOLOP = L(&quot;and&quot;) | L(&quot;or&quot;)

MARKER_VAR = VARIABLE | MARKER_VALUE

MARKER_ITEM = Group(MARKER_VAR + MARKER_OP + MARKER_VAR)
MARKER_ITEM.setParseAction(lambda s, l, t: tuple(t[0]))

LPAREN = L(&quot;(&quot;).suppress()
RPAREN = L(&quot;)&quot;).suppress()

MARKER_EXPR = Forward()
MARKER_ATOM = MARKER_ITEM | Group(LPAREN + MARKER_EXPR + RPAREN)
MARKER_EXPR &lt;&lt; MARKER_ATOM + ZeroOrMore(BOOLOP + MARKER_EXPR)

MARKER = stringStart + MARKER_EXPR + stringEnd


def _coerce_parse_result(results):
    if isinstance(results, ParseResults):
        return [_coerce_parse_result(i) for i in results]
    else:
        return results


def _format_marker(marker, first=True):
    assert isinstance(marker, (list, tuple, string_types))

    # Sometimes we have a structure like [[...]] which is a single item list
    # where the single item is itself it's own list. In that case we want skip
    # the rest of this function so that we don't get extraneous () on the
    # outside.
    if (isinstance(marker, list) and len(marker) == 1 and
            isinstance(marker[0], (list, tuple))):
        return _format_marker(marker[0])

    if isinstance(marker, list):
        inner = (_format_marker(m, first=False) for m in marker)
        if first:
            return &quot; &quot;.join(inner)
        else:
            return &quot;(&quot; + &quot; &quot;.join(inner) + &quot;)&quot;
    elif isinstance(marker, tuple):
        return &quot; &quot;.join([m.serialize() for m in marker])
    else:
        return marker


_operators = {
    &quot;in&quot;: lambda lhs, rhs: lhs in rhs,
    &quot;not in&quot;: lambda lhs, rhs: lhs not in rhs,
    &quot;&lt;&quot;: operator.lt,
    &quot;&lt;=&quot;: operator.le,
    &quot;==&quot;: operator.eq,
    &quot;!=&quot;: operator.ne,
    &quot;&gt;=&quot;: operator.ge,
    &quot;&gt;&quot;: operator.gt,
}


def _eval_op(lhs, op, rhs):
    try:
        spec = Specifier(&quot;&quot;.join([op.serialize(), rhs]))
    except InvalidSpecifier:
        pass
    else:
        return spec.contains(lhs)

    oper = _operators.get(op.serialize())
    if oper is None:
        raise UndefinedComparison(
            &quot;Undefined {0!r} on {1!r} and {2!r}.&quot;.format(op, lhs, rhs)
        )

    return oper(lhs, rhs)


_undefined = object()


def _get_env(environment, name):
    value = environment.get(name, _undefined)

    if value is _undefined:
        raise UndefinedEnvironmentName(
            &quot;{0!r} does not exist in evaluation environment.&quot;.format(name)
        )

    return value


def _evaluate_markers(markers, environment):
    groups = [[]]

    for marker in markers:
        assert isinstance(marker, (list, tuple, string_types))

        if isinstance(marker, list):
            groups[-1].append(_evaluate_markers(marker, environment))
        elif isinstance(marker, tuple):
            lhs, op, rhs = marker

            if isinstance(lhs, Variable):
                lhs_value = _get_env(environment, lhs.value)
                rhs_value = rhs.value
            else:
                lhs_value = lhs.value
                rhs_value = _get_env(environment, rhs.value)

            groups[-1].append(_eval_op(lhs_value, op, rhs_value))
        else:
            assert marker in [&quot;and&quot;, &quot;or&quot;]
            if marker == &quot;or&quot;:
                groups.append([])

    return any(all(item) for item in groups)


def format_full_version(info):
    version = '{0.major}.{0.minor}.{0.micro}'.format(info)
    kind = info.releaselevel
    if kind != 'final':
        version += kind[0] + str(info.serial)
    return version


def default_environment():
    if hasattr(sys, 'implementation'):
        iver = format_full_version(sys.implementation.version)
        implementation_name = sys.implementation.name
    else:
        iver = '0'
        implementation_name = ''

    return {
        &quot;implementation_name&quot;: implementation_name,
        &quot;implementation_version&quot;: iver,
        &quot;os_name&quot;: os.name,
        &quot;platform_machine&quot;: platform.machine(),
        &quot;platform_release&quot;: platform.release(),
        &quot;platform_system&quot;: platform.system(),
        &quot;platform_version&quot;: platform.version(),
        &quot;python_full_version&quot;: platform.python_version(),
        &quot;platform_python_implementation&quot;: platform.python_implementation(),
        &quot;python_version&quot;: platform.python_version()[:3],
        &quot;sys_platform&quot;: sys.platform,
    }


class Marker(object):

    def __init__(self, marker):
        try:
            self._markers = _coerce_parse_result(MARKER.parseString(marker))
        except ParseException as e:
            err_str = &quot;Invalid marker: {0!r}, parse error at {1!r}&quot;.format(
                marker, marker[e.loc:e.loc + 8])
            raise InvalidMarker(err_str)

    def __str__(self):
        return _format_marker(self._markers)

    def __repr__(self):
        return &quot;&lt;Marker({0!r})&gt;&quot;.format(str(self))

    def evaluate(self, environment=None):
        &quot;&quot;&quot;Evaluate a marker.

        Return the boolean from evaluating the given marker against the
        environment. environment is an optional argument to override all or
        part of the determined environment.

        The environment is determined from the current Python process.
        &quot;&quot;&quot;
        current_environment = default_environment()
        if environment is not None:
            current_environment.update(environment)

        return _evaluate_markers(self._markers, current_environment)
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