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
9from ..pgen2 import token
10from ..pygram import python_symbols as syms
11from .. import fixer_base
12from ..fixer_util import Name, Call, find_binding
13
14bind_warning = "Calls to builtin next() possibly shadowed by global binding"
15
16
17class 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
81def 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
93def 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
100def is_subtree(root, node):
101    if root == node:
102        return True
103    return any(is_subtree(c, node) for c in root.children)
104