trailing_wsp = to_encode[-1]

to_encode = to_encode[:-1]

new_last_ew = len(lines[-1]) if last_ew is None else last_ew

encode_as = 'utf-8' if charset == 'us-ascii' else charset

# The RFC2047 chrome takes up 7 characters plus the length

# of the charset name.

chrome_len = len(encode_as) + 7

if (chrome_len + 1) >= maxlen:

raise errors.HeaderParseError(

"max_line_length is too small to fit an encoded word")

while to_encode:

remaining_space = maxlen - len(lines[-1])

# The RFC2047 chrome takes up 7 characters plus the length

# of the charset name.

encode_as = 'utf-8' if charset == 'us-ascii' else charset

text_space = remaining_space - len(encode_as) - 7

text_space = remaining_space - chrome_len

if text_space <= 0:

lines.append(' ')

# XXX We'll get an infinite loop here if maxlen is <= 7

continue

to_encode_word = to_encode[:text_space]

from email._policybase import compat32

class Parser:

def __init__(self, _class=None, *, policy=compat32):

"""Parser of RFC 2822 and MIME email messages.

import types

import textwrap

import unittest

import email.errors

import email.policy

import email.parser

import email.generator

'Subject: \n' +

12 * ' =?utf-8?q?=C4=85?=\n')

def test_short_maxlen_error(self):

# RFC 2047 chrome takes up 7 characters, plus the length of the charset

# name, so folding should fail if maxlen is lower than the minimum

# required length for a line.

# Note: This is only triggered when there is a single word longer than

# max_line_length, hence the 1234567890 at the end of this whimsical

# subject. This is because when we encounter a word longer than

# max_line_length, it is broken down into encoded words to fit

# max_line_length. If the max_line_length isn't large enough to even

# contain the RFC 2047 chrome (`?=<charset>?q??=`), we fail.

subject = "Melt away the pounds with this one simple trick! 1234567890"

for maxlen in [3, 7, 9]:

with self.subTest(maxlen=maxlen):

policy = email.policy.default.clone(max_line_length=maxlen)

with self.assertRaises(email.errors.HeaderParseError):

policy.fold("Subject", subject)

# XXX: Need subclassing tests.

# For adding subclassed objects, make sure the usual rules apply (subclass

# wins), but that the order still works (right overrides left).

Fix infinite loop in email header folding logic that would be triggered when

an email policy's max_line_length is not long enough to include the required

markup and any values in the message. Patch by Paul Ganssle