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Text File  |  2006-08-03  |  2KB  |  74 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")
  20.  
  21.     def __init__(self):
  22.         self.found = {} # set
  23.  
  24.     def visitModule(self, node):
  25.         stmt = node.node
  26.         for s in stmt.nodes:
  27.             if not self.check_stmt(s):
  28.                 break
  29.  
  30.     def check_stmt(self, stmt):
  31.         if is_future(stmt):
  32.             for name, asname in stmt.names:
  33.                 if name in self.features:
  34.                     self.found[name] = 1
  35.                 else:
  36.                     raise SyntaxError, \
  37.                           "future feature %s is not defined" % name
  38.             stmt.valid_future = 1
  39.             return 1
  40.         return 0
  41.  
  42.     def get_features(self):
  43.         """Return list of features enabled by future statements"""
  44.         return self.found.keys()
  45.  
  46. class BadFutureParser:
  47.     """Check for invalid future statements"""
  48.  
  49.     def visitFrom(self, node):
  50.         if hasattr(node, 'valid_future'):
  51.             return
  52.         if node.modname != "__future__":
  53.             return
  54.         raise SyntaxError, "invalid future statement " + repr(node)
  55.  
  56. def find_futures(node):
  57.     p1 = FutureParser()
  58.     p2 = BadFutureParser()
  59.     walk(node, p1)
  60.     walk(node, p2)
  61.     return p1.get_features()
  62.  
  63. if __name__ == "__main__":
  64.     import sys
  65.     from compiler import parseFile, walk
  66.  
  67.     for file in sys.argv[1:]:
  68.         print file
  69.         tree = parseFile(file)
  70.         v = FutureParser()
  71.         walk(tree, v)
  72.         print v.found
  73.         print
  74.