"""Fixer for it.next() -> next(it), per PEP 3114."""

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# Author: Collin Winter

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# Things that currently aren't covered:

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# - listcomp "next" names aren't warned

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# - "with" statement targets aren't checked

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# Local imports

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from ..pgen2 import token

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from ..pygram import python_symbols as syms

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from .. import fixer_base

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from ..fixer_util import Name, Call, find_binding

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bind_warning = "Calls to builtin next() possibly shadowed by global binding"

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class FixNext(fixer_base.BaseFix):

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BM_compatible = True

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PATTERN = """

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power< base=any+ trailer< '.' attr='next' > trailer< '(' ')' > >

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|

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power< head=any+ trailer< '.' attr='next' > not trailer< '(' ')' > >

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|

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classdef< 'class' any+ ':'

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suite< any*

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funcdef< 'def'

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name='next'

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parameters< '(' NAME ')' > any+ >

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any* > >

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|

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global=global_stmt< 'global' any* 'next' any* >

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"""

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order = "pre" # Pre-order tree traversal

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def start_tree(self, tree, filename):

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super(FixNext, self).start_tree(tree, filename)

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n = find_binding('next', tree)

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if n:

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self.warning(n, bind_warning)

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self.shadowed_next = True

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else:

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self.shadowed_next = False

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def transform(self, node, results):

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assert results

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base = results.get("base")

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attr = results.get("attr")

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name = results.get("name")

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if base:

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if self.shadowed_next:

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attr.replace(Name("__next__", prefix=attr.prefix))

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else:

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base = [n.clone() for n in base]

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base[0].prefix = ""

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node.replace(Call(Name("next", prefix=node.prefix), base))

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elif name:

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n = Name("__next__", prefix=name.prefix)

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name.replace(n)

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elif attr:

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# We don't do this transformation if we're assigning to "x.next".

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# Unfortunately, it doesn't seem possible to do this in PATTERN,

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# so it's being done here.

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if is_assign_target(node):

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head = results["head"]

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if "".join([str(n) for n in head]).strip() == '__builtin__':

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self.warning(node, bind_warning)

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return

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attr.replace(Name("__next__"))

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elif "global" in results:

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self.warning(node, bind_warning)

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self.shadowed_next = True

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### The following functions help test if node is part of an assignment

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### target.

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def is_assign_target(node):

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assign = find_assign(node)

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if assign is None:

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return False

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for child in assign.children:

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if child.type == token.EQUAL:

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return False

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elif is_subtree(child, node):

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return True

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return False

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def find_assign(node):

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if node.type == syms.expr_stmt:

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return node

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if node.type == syms.simple_stmt or node.parent is None:

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return None

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return find_assign(node.parent)

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def is_subtree(root, node):

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if root == node:

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return True

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return any(is_subtree(c, node) for c in root.children)

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