Lib/compiler/future.py

   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