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Text File  |  2001-10-18  |  2KB  |  73 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.  
  20.     def __init__(self):
  21.         self.found = {} # set
  22.  
  23.     def visitModule(self, node):
  24.         stmt = node.node
  25.         for s in stmt.nodes:
  26.             if not self.check_stmt(s):
  27.                 break
  28.  
  29.     def check_stmt(self, stmt):
  30.         if is_future(stmt):
  31.             for name, asname in stmt.names:
  32.                 if name in self.features:
  33.                     self.found[name] = 1
  34.                 else:
  35.                     raise SyntaxError, \
  36.                           "future feature %s is not defined" % name
  37.             stmt.valid_future = 1
  38.             return 1
  39.         return 0
  40.  
  41.     def get_features(self):
  42.         """Return list of features enabled by future statements"""
  43.         return self.found.keys()
  44.  
  45. class BadFutureParser:
  46.     """Check for invalid future statements"""
  47.  
  48.     def visitFrom(self, node):
  49.         if hasattr(node, 'valid_future'):
  50.             return
  51.         if node.modname != "__future__":
  52.             return
  53.         raise SyntaxError, "invalid future statement"
  54.  
  55. def find_futures(node):
  56.     p1 = FutureParser()
  57.     p2 = BadFutureParser()
  58.     walk(node, p1)
  59.     walk(node, p2)
  60.     return p1.get_features()
  61.  
  62. if __name__ == "__main__":
  63.     import sys
  64.     from compiler import parseFile, walk
  65.  
  66.     for file in sys.argv[1:]:
  67.         print file
  68.         tree = parseFile(file)
  69.         v = FutureParser()
  70.         walk(tree, v)
  71.         print v.found
  72.         print
  73.