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# -*- coding: utf-8 -*-
"""Interpret PEP 345 environment markers.
EXPR [in|==|!=|not in] EXPR [or|and] ...
where EXPR belongs to any of those:
python_version = '%s.%s' % (sys.version_info[0], sys.version_info[1])
python_full_version = sys.version.split()[0]
os.name = os.name
sys.platform = sys.platform
platform.version = platform.version()
platform.machine = platform.machine()
platform.python_implementation = platform.python_implementation()
a free string, like '2.6', or 'win32'
"""
__all__ = ['default_environment', 'compile', 'interpret']
import ast
import os
import platform
import sys
import weakref
_builtin_compile = compile
try:
from platform import python_implementation
except ImportError:
if os.name == "java":
# Jython 2.5 has ast module, but not platform.python_implementation() function.
def python_implementation():
return "Jython"
else:
raise
# restricted set of variables
_VARS = {'sys.platform': sys.platform,
'python_version': '%s.%s' % sys.version_info[:2],
# FIXME parsing sys.platform is not reliable, but there is no other
# way to get e.g. 2.7.2+, and the PEP is defined with sys.version
'python_full_version': sys.version.split(' ', 1)[0],
'os.name': os.name,
'platform.version': platform.version(),
'platform.machine': platform.machine(),
'platform.python_implementation': python_implementation(),
'extra': None # wheel extension
}
for var in list(_VARS.keys()):
if '.' in var:
_VARS[var.replace('.', '_')] = _VARS[var]
def default_environment():
"""Return copy of default PEP 385 globals dictionary."""
return dict(_VARS)
class ASTWhitelist(ast.NodeTransformer):
def __init__(self, statement):
self.statement = statement # for error messages
ALLOWED = (ast.Compare, ast.BoolOp, ast.Attribute, ast.Name, ast.Load, ast.Str)
# Bool operations
ALLOWED += (ast.And, ast.Or)
# Comparison operations
ALLOWED += (ast.Eq, ast.Gt, ast.GtE, ast.In, ast.Is, ast.IsNot, ast.Lt, ast.LtE, ast.NotEq, ast.NotIn)
def visit(self, node):
"""Ensure statement only contains allowed nodes."""
if not isinstance(node, self.ALLOWED):
raise SyntaxError('Not allowed in environment markers.\n%s\n%s' %
(self.statement,
(' ' * node.col_offset) + '^'))
return ast.NodeTransformer.visit(self, node)
def visit_Attribute(self, node):
"""Flatten one level of attribute access."""
new_node = ast.Name("%s.%s" % (node.value.id, node.attr), node.ctx)
return ast.copy_location(new_node, node)
def parse_marker(marker):
tree = ast.parse(marker, mode='eval')
new_tree = ASTWhitelist(marker).generic_visit(tree)
return new_tree
def compile_marker(parsed_marker):
return _builtin_compile(parsed_marker, '<environment marker>', 'eval',
dont_inherit=True)
_cache = weakref.WeakValueDictionary()
def compile(marker):
"""Return compiled marker as a function accepting an environment dict."""
try:
return _cache[marker]
except KeyError:
pass
if not marker.strip():
def marker_fn(environment=None, override=None):
""""""
return True
else:
compiled_marker = compile_marker(parse_marker(marker))
def marker_fn(environment=None, override=None):
"""override updates environment"""
if override is None:
override = {}
if environment is None:
environment = default_environment()
environment.update(override)
return eval(compiled_marker, environment)
marker_fn.__doc__ = marker
_cache[marker] = marker_fn
return _cache[marker]
def interpret(marker, environment=None):
return compile(marker)(environment)
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