Tools/compiler/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",)
  19
  20     def __init__(self):
  21         self.found = {} # set
  22
  23     def visitModule(self, node):
  24         if node.doc is None:
  25             off = 0
  26         else:
  27             off = 1
  28
  29         stmt = node.node
  30         for s in stmt.nodes[off:]:
  31             if not self.check_stmt(s):
  32                 break
  33
  34     def check_stmt(self, stmt):
  35         if is_future(stmt):
  36             for name, asname in stmt.names:
  37                 if name in self.features:
  38                     self.found[name] = 1
  39                 else:
  40                     raise SyntaxError, \
  41                           "future feature %s is not defined" % name
  42             stmt.valid_future = 1
  43             return 1
  44         return 0
  45
  46     def get_features(self):
  47         """Return list of features enabled by future statements"""
  48         return self.found.keys()
  49
  50 class BadFutureParser:
  51     """Check for invalid future statements"""
  52
  53     def visitFrom(self, node):
  54         if hasattr(node, 'valid_future'):
  55             return
  56         if node.modname != "__future__":
  57             return
  58         raise SyntaxError, "invalid future statement"
  59
  60 def find_futures(node):
  61     p1 = FutureParser()
  62     p2 = BadFutureParser()
  63     walk(node, p1)
  64     walk(node, p2)
  65     return p1.get_features()
  66
  67 if __name__ == "__main__":
  68     import sys
  69     from compiler import parseFile, walk
  70
  71     for file in sys.argv[1:]:
  72         print file
  73         tree = parseFile(file)
  74         v = FutureParser()
  75         walk(tree, v)
  76         print v.found
  77         print
  78