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