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Filename : markers.py
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# 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 pyparsing import (  # noqa: N817
    Forward,
    Group,
    Literal as L,
    ParseException,
    ParseResults,
    QuotedString,
    ZeroOrMore,
    stringEnd,
    stringStart,
)

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

if TYPE_CHECKING:  # pragma: no cover
    from typing import Any, Callable, Dict, List, Optional, Tuple, Union

    Operator = Callable[[str, str], bool]


__all__ = [
    "InvalidMarker",
    "UndefinedComparison",
    "UndefinedEnvironmentName",
    "Marker",
    "default_environment",
]


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


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


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


class Node(object):
    def __init__(self, value):
        # type: (Any) -> None
        self.value = value

    def __str__(self):
        # type: () -> str
        return str(self.value)

    def __repr__(self):
        # type: () -> str
        return "<{0}({1!r})>".format(self.__class__.__name__, str(self))

    def serialize(self):
        # type: () -> str
        raise NotImplementedError


class Variable(Node):
    def serialize(self):
        # type: () -> str
        return str(self)


class Value(Node):
    def serialize(self):
        # type: () -> str
        return '"{0}"'.format(self)


class Op(Node):
    def serialize(self):
        # type: () -> str
        return str(self)


VARIABLE = (
    L("implementation_version")
    | L("platform_python_implementation")
    | L("implementation_name")
    | L("python_full_version")
    | L("platform_release")
    | L("platform_version")
    | L("platform_machine")
    | L("platform_system")
    | L("python_version")
    | L("sys_platform")
    | L("os_name")
    | L("os.name")  # PEP-345
    | L("sys.platform")  # PEP-345
    | L("platform.version")  # PEP-345
    | L("platform.machine")  # PEP-345
    | L("platform.python_implementation")  # PEP-345
    | L("python_implementation")  # undocumented setuptools legacy
    | L("extra")  # PEP-508
)
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("===") | L("==") | L(">=") | L("<=") | L("!=") | L("~=") | L(">") | L("<")
)

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

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

BOOLOP = L("and") | L("or")

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("(").suppress()
RPAREN = L(")").suppress()

MARKER_EXPR = Forward()
MARKER_ATOM = MARKER_ITEM | Group(LPAREN + MARKER_EXPR + RPAREN)
MARKER_EXPR << MARKER_ATOM + ZeroOrMore(BOOLOP + MARKER_EXPR)

MARKER = stringStart + MARKER_EXPR + stringEnd


def _coerce_parse_result(results):
    # type: (Union[ParseResults, List[Any]]) -> List[Any]
    if isinstance(results, ParseResults):
        return [_coerce_parse_result(i) for i in results]
    else:
        return results


def _format_marker(marker, first=True):
    # type: (Union[List[str], Tuple[Node, ...], str], Optional[bool]) -> str

    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 " ".join(inner)
        else:
            return "(" + " ".join(inner) + ")"
    elif isinstance(marker, tuple):
        return " ".join([m.serialize() for m in marker])
    else:
        return marker


_operators = {
    "in": lambda lhs, rhs: lhs in rhs,
    "not in": lambda lhs, rhs: lhs not in rhs,
    "<": operator.lt,
    "<=": operator.le,
    "==": operator.eq,
    "!=": operator.ne,
    ">=": operator.ge,
    ">": operator.gt,
}  # type: Dict[str, Operator]


def _eval_op(lhs, op, rhs):
    # type: (str, Op, str) -> bool
    try:
        spec = Specifier("".join([op.serialize(), rhs]))
    except InvalidSpecifier:
        pass
    else:
        return spec.contains(lhs)

    oper = _operators.get(op.serialize())  # type: Optional[Operator]
    if oper is None:
        raise UndefinedComparison(
            "Undefined {0!r} on {1!r} and {2!r}.".format(op, lhs, rhs)
        )

    return oper(lhs, rhs)


class Undefined(object):
    pass


_undefined = Undefined()


def _get_env(environment, name):
    # type: (Dict[str, str], str) -> str
    value = environment.get(name, _undefined)  # type: Union[str, Undefined]

    if isinstance(value, Undefined):
        raise UndefinedEnvironmentName(
            "{0!r} does not exist in evaluation environment.".format(name)
        )

    return value


def _evaluate_markers(markers, environment):
    # type: (List[Any], Dict[str, str]) -> bool
    groups = [[]]  # type: List[List[bool]]

    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 ["and", "or"]
            if marker == "or":
                groups.append([])

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


def format_full_version(info):
    # type: (sys._version_info) -> str
    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():
    # type: () -> Dict[str, str]
    if hasattr(sys, "implementation"):
        # Ignoring the `sys.implementation` reference for type checking due to
        # mypy not liking that the attribute doesn't exist in Python 2.7 when
        # run with the `--py27` flag.
        iver = format_full_version(sys.implementation.version)  # type: ignore
        implementation_name = sys.implementation.name  # type: ignore
    else:
        iver = "0"
        implementation_name = ""

    return {
        "implementation_name": implementation_name,
        "implementation_version": iver,
        "os_name": os.name,
        "platform_machine": platform.machine(),
        "platform_release": platform.release(),
        "platform_system": platform.system(),
        "platform_version": platform.version(),
        "python_full_version": platform.python_version(),
        "platform_python_implementation": platform.python_implementation(),
        "python_version": ".".join(platform.python_version_tuple()[:2]),
        "sys_platform": sys.platform,
    }


class Marker(object):
    def __init__(self, marker):
        # type: (str) -> None
        try:
            self._markers = _coerce_parse_result(MARKER.parseString(marker))
        except ParseException as e:
            err_str = "Invalid marker: {0!r}, parse error at {1!r}".format(
                marker, marker[e.loc : e.loc + 8]
            )
            raise InvalidMarker(err_str)

    def __str__(self):
        # type: () -> str
        return _format_marker(self._markers)

    def __repr__(self):
        # type: () -> str
        return "<Marker({0!r})>".format(str(self))

    def evaluate(self, environment=None):
        # type: (Optional[Dict[str, str]]) -> bool
        """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.
        """
        current_environment = default_environment()
        if environment is not None:
            current_environment.update(environment)

        return _evaluate_markers(self._markers, current_environment)