UTF-7 codec decodes ill-formed sequences starting with "+"

[jwilk]

BPO	22602
Nosy	@malemburg, @loewis, @vstinner, @jwilk, @ezio-melotti, @serhiy-storchaka, @ZackerySpytz
PRs	bpo-22602: Raise an exception in the UTF-7 decoder for ill-formed sequences starting with "+" #8741

^{Note: these values reflect the state of the issue at the time it was migrated and might not reflect the current state.}

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GitHub fields:

assignee = None
closed_at = <Date 2018-08-19.04:44:28.301>
created_at = <Date 2014-10-10.12:44:43.923>
labels = ['interpreter-core', 'type-bug', '3.8', 'expert-unicode']
title = 'UTF-7 codec decodes ill-formed sequences starting with "+"'
updated_at = <Date 2018-08-19.04:44:28.300>
user = 'https://github.com/jwilk'

bugs.python.org fields:

activity = <Date 2018-08-19.04:44:28.300>
actor = 'serhiy.storchaka'
assignee = 'none'
closed = True
closed_date = <Date 2018-08-19.04:44:28.301>
closer = 'serhiy.storchaka'
components = ['Interpreter Core', 'Unicode']
creation = <Date 2014-10-10.12:44:43.923>
creator = 'jwilk'
dependencies = []
files = []
hgrepos = []
issue_num = 22602
keywords = ['patch']
message_count = 5.0
messages = ['228996', '323431', '323444', '323742', '323743']
nosy_count = 7.0
nosy_names = ['lemburg', 'loewis', 'vstinner', 'jwilk', 'ezio.melotti', 'serhiy.storchaka', 'ZackerySpytz']
pr_nums = ['8741']
priority = 'normal'
resolution = 'fixed'
stage = 'resolved'
status = 'closed'
superseder = None
type = 'behavior'
url = 'https://bugs.python.org/issue22602'
versions = ['Python 3.8']

[jwilk]

RFC 2152 reads:

A "+" character followed immediately by any character other than
members of set B or "-" is an ill-formed sequence.

"@" is not a member of B, so I would expect this to raise UnicodeDecodeError:

>>> b'+@'.decode('UTF-7')
'@'

[ZackerySpytz]

This was also mentioned in bpo-24848.

[serhiy-storchaka]

What about a "+" character followed immediately by the end of the bytestring?

>>> b'+'.decode('utf-7')
''

[serhiy-storchaka]

New changeset e349bf2 by Serhiy Storchaka (Zackery Spytz) in branch 'master':
bpo-22602: Raise an exception in the UTF-7 decoder for ill-formed sequences starting with "+". (GH-8741)
e349bf2

[serhiy-storchaka]

Thank you for your PR Zackery.