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Python Source  |  2011-02-15  |  3.1 KB  |  104 lines
  1. """Fixer for it.next() -> next(it), per PEP 3114."""
  2. # Author: Collin Winter
  3.  
  4. # Things that currently aren't covered:
  5. #   - listcomp "next" names aren't warned
  6. #   - "with" statement targets aren't checked
  7.  
  8. # Local imports
  9. from ..pgen2 import token
  10. from ..pygram import python_symbols as syms
  11. from .. import fixer_base
  12. from ..fixer_util import Name, Call, find_binding
  13.  
  14. bind_warning = "Calls to builtin next() possibly shadowed by global binding"
  15.  
  16.  
  17. class FixNext(fixer_base.BaseFix):
  18.     PATTERN = """
  19.     power< base=any+ trailer< '.' attr='next' > trailer< '(' ')' > >
  20.     |
  21.     power< head=any+ trailer< '.' attr='next' > not trailer< '(' ')' > >
  22.     |
  23.     classdef< 'class' any+ ':'
  24.               suite< any*
  25.                      funcdef< 'def'
  26.                               name='next'
  27.                               parameters< '(' NAME ')' > any+ >
  28.                      any* > >
  29.     |
  30.     global=global_stmt< 'global' any* 'next' any* >
  31.     """
  32.  
  33.     order = "pre" # Pre-order tree traversal
  34.  
  35.     def start_tree(self, tree, filename):
  36.         super(FixNext, self).start_tree(tree, filename)
  37.  
  38.         n = find_binding('next', tree)
  39.         if n:
  40.             self.warning(n, bind_warning)
  41.             self.shadowed_next = True
  42.         else:
  43.             self.shadowed_next = False
  44.  
  45.     def transform(self, node, results):
  46.         assert results
  47.  
  48.         base = results.get("base")
  49.         attr = results.get("attr")
  50.         name = results.get("name")
  51.         mod = results.get("mod")
  52.  
  53.         if base:
  54.             if self.shadowed_next:
  55.                 attr.replace(Name("__next__", prefix=attr.get_prefix()))
  56.             else:
  57.                 base = [n.clone() for n in base]
  58.                 base[0].set_prefix("")
  59.                 node.replace(Call(Name("next", prefix=node.get_prefix()), base))
  60.         elif name:
  61.             n = Name("__next__", prefix=name.get_prefix())
  62.             name.replace(n)
  63.         elif attr:
  64.             # We don't do this transformation if we're assigning to "x.next".
  65.             # Unfortunately, it doesn't seem possible to do this in PATTERN,
  66.             #  so it's being done here.
  67.             if is_assign_target(node):
  68.                 head = results["head"]
  69.                 if "".join([str(n) for n in head]).strip() == '__builtin__':
  70.                     self.warning(node, bind_warning)
  71.                 return
  72.             attr.replace(Name("__next__"))
  73.         elif "global" in results:
  74.             self.warning(node, bind_warning)
  75.             self.shadowed_next = True
  76.  
  77.  
  78. ### The following functions help test if node is part of an assignment
  79. ###  target.
  80.  
  81. def is_assign_target(node):
  82.     assign = find_assign(node)
  83.     if assign is None:
  84.         return False
  85.  
  86.     for child in assign.children:
  87.         if child.type == token.EQUAL:
  88.             return False
  89.         elif is_subtree(child, node):
  90.             return True
  91.     return False
  92.  
  93. def find_assign(node):
  94.     if node.type == syms.expr_stmt:
  95.         return node
  96.     if node.type == syms.simple_stmt or node.parent is None:
  97.         return None
  98.     return find_assign(node.parent)
  99.  
  100. def is_subtree(root, node):
  101.     if root == node:
  102.         return True
  103.     return any([is_subtree(c, node) for c in root.children])
  104.