Incorrect iteration of Manager.dict() method of the multiprocessing module.

[deltaclock]

BPO	34610
Nosy	@pitrou, @benjaminp, @serhiy-storchaka, @applio, @miss-islington, @deltaclock
PRs	bpo-34610: Fixed iterator of multiprocessing.managers.DictProxy. #9113 [3.7] bpo-34610: Fixed iterator of multiprocessing.managers.DictProxy. (GH-9113) #9349 [3.6] bpo-34610: Fixed iterator of multiprocessing.managers.DictProxy. (GH-9113) #9350 [2.7] bpo-34610: Fixed iterator of multiprocessing.managers.DictProxy (GH-9113). #9500
Files	test.py: Proof of concept code.

^{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 2018-09-22.18:35:26.970>
created_at = <Date 2018-09-07.23:43:37.917>
labels = ['3.7', '3.8', 'type-bug', 'library']
title = 'Incorrect iteration of Manager.dict() method of the multiprocessing module.'
updated_at = <Date 2018-09-22.18:35:26.969>
user = 'https://github.com/deltaclock'

bugs.python.org fields:

activity = <Date 2018-09-22.18:35:26.969>
actor = 'serhiy.storchaka'
assignee = 'none'
closed = True
closed_date = <Date 2018-09-22.18:35:26.970>
closer = 'serhiy.storchaka'
components = ['Library (Lib)']
creation = <Date 2018-09-07.23:43:37.917>
creator = 'deltaclock'
dependencies = []
files = ['47792']
hgrepos = []
issue_num = 34610
keywords = ['patch']
message_count = 6.0
messages = ['324813', '324820', '325522', '325528', '325529', '326107']
nosy_count = 6.0
nosy_names = ['pitrou', 'benjamin.peterson', 'serhiy.storchaka', 'davin', 'miss-islington', 'deltaclock']
pr_nums = ['9113', '9349', '9350', '9500']
priority = 'normal'
resolution = 'fixed'
stage = 'resolved'
status = 'closed'
superseder = None
type = 'behavior'
url = 'https://bugs.python.org/issue34610'
versions = ['Python 2.7', 'Python 3.6', 'Python 3.7', 'Python 3.8']

[deltaclock]

The manager class of the multiprocessing module doesnt implement __next__ or __iter__ on its dictionary method and relies on using __getitem__.

This results in an unexpected functionality of an object that is supposed to act like a dict, and instead of looping over the dictionary keys it loops over its values.

The user needs to call dict() on this object in order to loop over it correctly, which is not that obvious.

The problem originates from there https://github.com/python/cpython/blob/master/Lib/multiprocessing/managers.py#L1136

Poc link: https://hastebin.com/codoqihowi.py

[serhiy-storchaka]

DictProxy needs to provide the __iter__() method. And perhaps methods keys(), values() and items() need to be reworked in Python 3. has_key() is unneeded in Python 3.

It is worth to test also other special and new in Python 3 methods.

[serhiy-storchaka]

New changeset e0e5065 by Serhiy Storchaka in branch 'master':
bpo-34610: Fixed iterator of multiprocessing.managers.DictProxy. (GH-9113)
e0e5065

[miss-islington]

New changeset 1d30788 by Miss Islington (bot) in branch '3.7':
bpo-34610: Fixed iterator of multiprocessing.managers.DictProxy. (GH-9113)
1d30788

[miss-islington]

New changeset f35e4d5 by Miss Islington (bot) in branch '3.6':
bpo-34610: Fixed iterator of multiprocessing.managers.DictProxy. (GH-9113)
f35e4d5

[serhiy-storchaka]

New changeset 69d0bc1 by Serhiy Storchaka in branch '2.7':
[2.7] bpo-34610: Fixed iterator of multiprocessing.managers.DictProxy. (GH-9113). (GH-9500)
69d0bc1