"""Parser for future statements

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"""

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from compiler import ast, walk

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def is_future(stmt):

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"""Return true if statement is a well-formed future statement"""

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if not isinstance(stmt, ast.From):

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return 0

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if stmt.modname == "__future__":

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return 1

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else:

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return 0

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class FutureParser:

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features = ("nested_scopes", "generators", "division",

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"absolute_import", "with_statement", "print_function",

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"unicode_literals")

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def __init__(self):

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self.found = {} # set

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def visitModule(self, node):

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stmt = node.node

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for s in stmt.nodes:

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if not self.check_stmt(s):

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break

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def check_stmt(self, stmt):

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if is_future(stmt):

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for name, asname in stmt.names:

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if name in self.features:

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self.found[name] = 1

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else:

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raise SyntaxError, \

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"future feature %s is not defined" % name

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stmt.valid_future = 1

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return 1

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return 0

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def get_features(self):

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"""Return list of features enabled by future statements"""

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return self.found.keys()

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class BadFutureParser:

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"""Check for invalid future statements"""

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def visitFrom(self, node):

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if hasattr(node, 'valid_future'):

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return

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if node.modname != "__future__":

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return

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raise SyntaxError, "invalid future statement " + repr(node)

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def find_futures(node):

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p1 = FutureParser()

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p2 = BadFutureParser()

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walk(node, p1)

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walk(node, p2)

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return p1.get_features()

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if __name__ == "__main__":

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import sys

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from compiler import parseFile, walk

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for file in sys.argv[1:]:

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print file

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tree = parseFile(file)

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v = FutureParser()

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walk(tree, v)

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print v.found

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print

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