"""
Based on fix_next.py by Collin Winter.
Replaces it.next() -> next(it), per PEP 3114.
Unlike fix_next.py, this fixer doesn't replace the name of a next method with __next__,
which would break Python 2 compatibility without further help from fixers in
stage 2.
"""
# Local imports
from lib2to3.pgen2 import token
from lib2to3.pygram import python_symbols as syms
from lib2to3 import fixer_base
from lib2to3.fixer_util import Name, Call, find_binding
bind_warning = "Calls to builtin next() possibly shadowed by global binding"
class FixNextCall(fixer_base.BaseFix):
BM_compatible = True
PATTERN = """
power< base=any+ trailer< '.' attr='next' > trailer< '(' ')' > >
|
power< head=any+ trailer< '.' attr='next' > not trailer< '(' ')' > >
|
global=global_stmt< 'global' any* 'next' any* >
"""
order = "pre" # Pre-order tree traversal
def start_tree(self, tree, filename):
super(FixNextCall, self).start_tree(tree, filename)
n = find_binding('next', tree)
if n:
self.warning(n, bind_warning)
self.shadowed_next = True
else:
self.shadowed_next = False
def transform(self, node, results):
assert results
base = results.get("base")
attr = results.get("attr")
name = results.get("name")
if base:
if self.shadowed_next:
# Omit this:
# attr.replace(Name("__next__", prefix=attr.prefix))
pass
else:
base = [n.clone() for n in base]
base[0].prefix = ""
node.replace(Call(Name("next", prefix=node.prefix), base))
elif name:
# Omit this:
# n = Name("__next__", prefix=name.prefix)
# name.replace(n)
pass
elif attr:
# We don't do this transformation if we're assigning to "x.next".
# Unfortunately, it doesn't seem possible to do this in PATTERN,
# so it's being done here.
if is_assign_target(node):
head = results["head"]
if "".join([str(n) for n in head]).strip() == '__builtin__':
self.warning(node, bind_warning)
return
# Omit this:
# attr.replace(Name("__next__"))
elif "global" in results:
self.warning(node, bind_warning)
self.shadowed_next = True
### The following functions help test if node is part of an assignment
### target.
def is_assign_target(node):
assign = find_assign(node)
if assign is None:
return False
for child in assign.children:
if child.type == token.EQUAL:
return False
elif is_subtree(child, node):
return True
return False
def find_assign(node):
if node.type == syms.expr_stmt:
return node
if node.type == syms.simple_stmt or node.parent is None:
return None
return find_assign(node.parent)
def is_subtree(root, node):
if root == node:
return True
return any(is_subtree(c, node) for c in root.children)
