"""
For the ``future`` package.
Adds this import line:
from past.builtins import str as oldstr
at the top and wraps any unadorned string literals 'abc' or explicit byte-string
literals b'abc' in oldstr() calls so the code has the same behaviour on Py3 as
on Py2.6/2.7.
"""
from __future__ import unicode_literals
import re
from lib2to3 import fixer_base
from lib2to3.pgen2 import token
from lib2to3.fixer_util import syms
from libfuturize.fixer_util import (future_import, touch_import_top,
wrap_in_fn_call)
_literal_re = re.compile(r"[^uUrR]?[\'\"]")
class FixOldstrWrap(fixer_base.BaseFix):
BM_compatible = True
PATTERN = "STRING"
def transform(self, node, results):
if node.type == token.STRING:
touch_import_top(u'past.types', u'oldstr', node)
if _literal_re.match(node.value):
new = node.clone()
# Strip any leading space or comments:
# TODO: check: do we really want to do this?
new.prefix = u''
new.value = u'b' + new.value
wrapped = wrap_in_fn_call("oldstr", [new], prefix=node.prefix)
return wrapped
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