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
  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