imaplib cannot handle mailboxes with ACL: lrs

[chaoflow]

BPO	1749512
Nosy	@warsaw, @bitdancer
Files	python-imaplib.patch

^{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 = None
created_at = <Date 2007-07-07.07:52:44.000>
labels = ['type-bug', 'library', 'expert-email']
title = 'imaplib cannot handle mailboxes with ACL: lrs'
updated_at = <Date 2015-10-24.14:59:22.536>
user = 'https://bugs.python.org/chaoflow'

bugs.python.org fields:

activity = <Date 2015-10-24.14:59:22.536>
actor = 'serhiy.storchaka'
assignee = 'none'
closed = False
closed_date = None
closer = None
components = ['Library (Lib)', 'email']
creation = <Date 2007-07-07.07:52:44.000>
creator = 'chaoflow'
dependencies = []
files = ['2417']
hgrepos = []
issue_num = 1749512
keywords = ['patch']
message_count = 2.0
messages = ['32455', '116701']
nosy_count = 3.0
nosy_names = ['barry', 'chaoflow', 'r.david.murray']
pr_nums = []
priority = 'normal'
resolution = None
stage = 'test needed'
status = 'open'
superseder = None
type = 'behavior'
url = 'https://bugs.python.org/issue1749512'
versions = ['Python 2.7', 'Python 3.4', 'Python 3.5', 'Python 3.6']

Linked PRs

• gh-45154: Fix imaplib handling of READ-ONLY mailboxes #141709

[chaoflow]

The imaplib in python 2.4 and 2.5 is not able to handle a mailbox with ACL set to lrs correctly, as it treats it the same as a mailbox opened with EXAMINE. A mailbox with lrs can save \Seen flags, a mailbox opened with EXAMINE cannot.

The attached patch is giving a proposal on how to fix it.

The current select raises an exception, in case the server tells READ-ONLY in a response. However, for lrs this is the case, but nevertheless, it is possible to save per-use state information.

With the patch this is not the case anymore. A readonly exception is only raised in case of an lr mailbox, as that is an equivalent to a mailbox opened with EXAMINE, i.e. select(..., readonly=True). A READ-ONLY in the response to a select is saved in self.is_readonly. Programs who relied on an exception being raised during select, would now need to query that variable.

In case the state was not READ-ONLY during select, but becomes at some later point during command execution, still a readonly exception is raised.

The patched imaplib was tested successfully with a slightly adapted offlineimap.

[BreamoreBoy]

@florian this won't go anywhere unles the patch includes doc and unit test changes.