Issue 33524: non-ascii characters in headers causes TypeError on email.policy.Policy.fold (original) (raw)

Python 3.6.5 has trouble on folding email messages:

Traceback (most recent call last): File "emailtest.py", line 7, in policy.fold("Subject", msg["Subject"]) File "/usr/lib/python3.6/email/policy.py", line 183, in fold return self._fold(name, value, refold_binary=True) File "/usr/lib/python3.6/email/policy.py", line 205, in _fold return value.fold(policy=self) File "/usr/lib/python3.6/email/headerregistry.py", line 258, in fold return header.fold(policy=policy) File "/usr/lib/python3.6/email/_header_value_parser.py", line 144, in fold return _refold_parse_tree(self, policy=policy) File "/usr/lib/python3.6/email/_header_value_parser.py", line 2651, in _refold_parse_tree part.ew_combine_allowed, charset) File "/usr/lib/python3.6/email/_header_value_parser.py", line 2728, in _fold_as_ew first_part = to_encode[:text_space] TypeError: slice indices must be integers or None or have an index method

The message has non-ascii characters in header and set max_line_length=0, regardless length of the header. Here is the code to reproduce.

from email.message import EmailMessage from email.policy import default

policy = default.clone(max_line_length=0) msg = EmailMessage() msg["Subject"] = "á" policy.fold("Subject", msg["Subject"])

I first found this issue on Maildir.add, which saves the message to a file without word wrap.

Oh, interesting.

I could argue that that's a missing feature in Python's slice handling. The value of text_space at that point is '+inf', and I obviously incorrectly assumed that slicing would treat that as if it were [:]. The counter argument, of course, is that inf is a float not an integer. I suppose we'll have to use sys.maxsize instead.