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     BM_compatible = True
19     PATTERN = """
20     power< base=any+ trailer< '.' attr='next' > trailer< '(' ')' > >
21     |
22     power< head=any+ trailer< '.' attr='next' > not trailer< '(' ')' > >
23     |
24     classdef< 'class' any+ ':'
25               suite< any*
26                      funcdef< 'def'
27                               name='next'
28                               parameters< '(' NAME ')' > any+ >
29                      any* > >
30     |
31     global=global_stmt< 'global' any* 'next' any* >
32     """
33 
34     order = "pre" # Pre-order tree traversal
35 
36     def start_tree(self, tree, filename):
37         super(FixNext, self).start_tree(tree, filename)
38 
39         n = find_binding(u'next', tree)
40         if n:
41             self.warning(n, bind_warning)
42             self.shadowed_next = True
43         else:
44             self.shadowed_next = False
45 
46     def transform(self, node, results):
47         assert results
48 
49         base = results.get("base")
50         attr = results.get("attr")
51         name = results.get("name")
52 
53         if base:
54             if self.shadowed_next:
55                 attr.replace(Name(u"__next__", prefix=attr.prefix))
56             else:
57                 base = [n.clone() for n in base]
58                 base[0].prefix = u""
59                 node.replace(Call(Name(u"next", prefix=node.prefix), base))
60         elif name:
61             n = Name(u"__next__", prefix=name.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() == u'__builtin__':
70                     self.warning(node, bind_warning)
71                 return
72             attr.replace(Name(u"__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