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])