Edit: markers.py
# -*- coding: utf-8 -*- # # Copyright (C) 2012-2017 Vinay Sajip. # Licensed to the Python Software Foundation under a contributor agreement. # See LICENSE.txt and CONTRIBUTORS.txt. # """ Parser for the environment markers micro-language defined in PEP 508. """ # Note: In PEP 345, the micro-language was Python compatible, so the ast # module could be used to parse it. However, PEP 508 introduced operators such # as ~= and === which aren't in Python, necessitating a different approach. import os import re import sys import platform from .compat import string_types from .util import in_venv, parse_marker from .version import NormalizedVersion as NV __all__ = ['interpret'] _VERSION_PATTERN = re.compile(r'((\d+(\.\d+)*\w*)|\'(\d+(\.\d+)*\w*)\'|\"(\d+(\.\d+)*\w*)\")') def _is_literal(o): if not isinstance(o, string_types) or not o: return False return o[0] in '\'"' def _get_versions(s): result = [] for m in _VERSION_PATTERN.finditer(s): result.append(NV(m.groups()[0])) return set(result) class Evaluator(object): """ This class is used to evaluate marker expessions. """ operations = { '==': lambda x, y: x == y, '===': lambda x, y: x == y, '~=': lambda x, y: x == y or x > y, '!=': lambda x, y: x != y, '<': lambda x, y: x < y, '<=': lambda x, y: x == y or x < y, '>': lambda x, y: x > y, '>=': lambda x, y: x == y or x > y, 'and': lambda x, y: x and y, 'or': lambda x, y: x or y, 'in': lambda x, y: x in y, 'not in': lambda x, y: x not in y, } def evaluate(self, expr, context): """ Evaluate a marker expression returned by the :func:`parse_requirement` function in the specified context. """ if isinstance(expr, string_types): if expr[0] in '\'"': result = expr[1:-1] else: if expr not in context: raise SyntaxError('unknown variable: %s' % expr) result = context[expr] else: assert isinstance(expr, dict) op = expr['op'] if op not in self.operations: raise NotImplementedError('op not implemented: %s' % op) elhs = expr['lhs'] erhs = expr['rhs'] if _is_literal(expr['lhs']) and _is_literal(expr['rhs']): raise SyntaxError('invalid comparison: %s %s %s' % (elhs, op, erhs)) lhs = self.evaluate(elhs, context) rhs = self.evaluate(erhs, context) if ((elhs == 'python_version' or erhs == 'python_version') and op in ('<', '<=', '>', '>=', '===', '==', '!=', '~=')): lhs = NV(lhs) rhs = NV(rhs) elif elhs == 'python_version' and op in ('in', 'not in'): lhs = NV(lhs) rhs = _get_versions(rhs) result = self.operations[op](lhs, rhs) return result _DIGITS = re.compile(r'\d+\.\d+') def default_context(): def format_full_version(info): version = '%s.%s.%s' % (info.major, info.minor, info.micro) kind = info.releaselevel if kind != 'final': version += kind[0] + str(info.serial) return version if hasattr(sys, 'implementation'): implementation_version = format_full_version(sys.implementation.version) implementation_name = sys.implementation.name else: implementation_version = '0' implementation_name = '' ppv = platform.python_version() m = _DIGITS.match(ppv) pv = m.group(0) result = { 'implementation_name': implementation_name, 'implementation_version': implementation_version, 'os_name': os.name, 'platform_machine': platform.machine(), 'platform_python_implementation': platform.python_implementation(), 'platform_release': platform.release(), 'platform_system': platform.system(), 'platform_version': platform.version(), 'platform_in_venv': str(in_venv()), 'python_full_version': ppv, 'python_version': pv, 'sys_platform': sys.platform, } return result DEFAULT_CONTEXT = default_context() del default_context evaluator = Evaluator() def interpret(marker, execution_context=None): """ Interpret a marker and return a result depending on environment. :param marker: The marker to interpret. :type marker: str :param execution_context: The context used for name lookup. :type execution_context: mapping """ try: expr, rest = parse_marker(marker) except Exception as e: raise SyntaxError('Unable to interpret marker syntax: %s: %s' % (marker, e)) if rest and rest[0] != '#': raise SyntaxError('unexpected trailing data in marker: %s: %s' % (marker, rest)) context = dict(DEFAULT_CONTEXT) if execution_context: context.update(execution_context) return evaluator.evaluate(expr, context)
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