| 1 | """Parser for future statements"""
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| 2 |
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| 3 | from . import ast
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| 4 | from .visitor import ASTVisitor
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| 5 |
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| 6 |
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| 7 | def is_future(stmt):
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| 8 | """Return true if statement is a well-formed future statement"""
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| 9 | if not isinstance(stmt, ast.From):
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| 10 | return 0
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| 11 | if stmt.modname == "__future__":
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| 12 | return 1
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| 13 | else:
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| 14 | return 0
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| 15 |
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| 16 |
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| 17 | class FutureParser(ASTVisitor):
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| 18 |
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| 19 | features = ("nested_scopes", "generators", "division",
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| 20 | "absolute_import", "with_statement", "print_function",
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| 21 | "unicode_literals")
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| 22 |
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| 23 | def __init__(self):
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| 24 | ASTVisitor.__init__(self)
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| 25 | self.found = {} # set
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| 26 |
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| 27 | def visitModule(self, node):
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| 28 | stmt = node.node
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| 29 | for s in stmt.nodes:
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| 30 | if not self.check_stmt(s):
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| 31 | break
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| 32 |
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| 33 | def check_stmt(self, stmt):
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| 34 | if is_future(stmt):
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| 35 | for name, asname in stmt.names:
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| 36 | if name in self.features:
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| 37 | self.found[name] = 1
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| 38 | else:
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| 39 | raise SyntaxError, \
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| 40 | "future feature %s is not defined" % name
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| 41 | stmt.valid_future = 1
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| 42 | return 1
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| 43 | return 0
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| 44 |
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| 45 | def get_features(self):
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| 46 | """Return list of features enabled by future statements"""
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| 47 | return self.found.keys()
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| 48 |
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| 49 |
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| 50 | class BadFutureParser(ASTVisitor):
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| 51 | """Check for invalid future statements"""
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| 52 |
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| 53 | def visitFrom(self, node):
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| 54 | if hasattr(node, 'valid_future'):
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| 55 | return
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| 56 | if node.modname != "__future__":
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| 57 | return
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| 58 | raise SyntaxError, "invalid future statement " + repr(node)
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