1"""
2For the ``future`` package.
3
4Adds this import line:
5
6    from past.builtins import str as oldstr
7
8at the top and wraps any unadorned string literals 'abc' or explicit byte-string
9literals b'abc' in oldstr() calls so the code has the same behaviour on Py3 as
10on Py2.6/2.7.
11"""
12
13from __future__ import unicode_literals
14import re
15from lib2to3 import fixer_base
16from lib2to3.pgen2 import token
17from lib2to3.fixer_util import syms
18from libfuturize.fixer_util import (future_import, touch_import_top,
19                                    wrap_in_fn_call)
20
21
22_literal_re = re.compile(r"[^uUrR]?[\'\"]")
23
24
25class FixOldstrWrap(fixer_base.BaseFix):
26    BM_compatible = True
27    PATTERN = "STRING"
28
29    def transform(self, node, results):
30        if node.type == token.STRING:
31            touch_import_top(u'past.types', u'oldstr', node)
32            if _literal_re.match(node.value):
33                new = node.clone()
34                # Strip any leading space or comments:
35                # TODO: check: do we really want to do this?
36                new.prefix = u''
37                new.value = u'b' + new.value
38                wrapped = wrap_in_fn_call("oldstr", [new], prefix=node.prefix)
39                return wrapped
40