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Text File  |  2009-11-02  |  2KB  |  75 lines
  1. """Parser for future statements
  2.  
  3. """
  4.  
  5. from compiler import ast, walk
  6.  
  7. def is_future(stmt):
  8.     """Return true if statement is a well-formed future statement"""
  9.     if not isinstance(stmt, ast.From):
  10.         return 0
  11.     if stmt.modname == "__future__":
  12.         return 1
  13.     else:
  14.         return 0
  15.  
  16. class FutureParser:
  17.  
  18.     features = ("nested_scopes", "generators", "division",
  19.                 "absolute_import", "with_statement", "print_function",
  20.                 "unicode_literals")
  21.  
  22.     def __init__(self):
  23.         self.found = {} # set
  24.  
  25.     def visitModule(self, node):
  26.         stmt = node.node
  27.         for s in stmt.nodes:
  28.             if not self.check_stmt(s):
  29.                 break
  30.  
  31.     def check_stmt(self, stmt):
  32.         if is_future(stmt):
  33.             for name, asname in stmt.names:
  34.                 if name in self.features:
  35.                     self.found[name] = 1
  36.                 else:
  37.                     raise SyntaxError, \
  38.                           "future feature %s is not defined" % name
  39.             stmt.valid_future = 1
  40.             return 1
  41.         return 0
  42.  
  43.     def get_features(self):
  44.         """Return list of features enabled by future statements"""
  45.         return self.found.keys()
  46.  
  47. class BadFutureParser:
  48.     """Check for invalid future statements"""
  49.  
  50.     def visitFrom(self, node):
  51.         if hasattr(node, 'valid_future'):
  52.             return
  53.         if node.modname != "__future__":
  54.             return
  55.         raise SyntaxError, "invalid future statement " + repr(node)
  56.  
  57. def find_futures(node):
  58.     p1 = FutureParser()
  59.     p2 = BadFutureParser()
  60.     walk(node, p1)
  61.     walk(node, p2)
  62.     return p1.get_features()
  63.  
  64. if __name__ == "__main__":
  65.     import sys
  66.     from compiler import parseFile, walk
  67.  
  68.     for file in sys.argv[1:]:
  69.         print file
  70.         tree = parseFile(file)
  71.         v = FutureParser()
  72.         walk(tree, v)
  73.         print v.found
  74.         print
  75.