email.utils.getaddresses does not handle Header objects

[frispete]

BPO	27513
Nosy	@warsaw, @bitdancer, @ambv, @ZackerySpytz, @miss-islington, @tirkarthi, @websurfer5
PRs	bpo-27513: email.utils.getaddresses() now handles Header objects #13797 [3.10] bpo-27513: email.utils.getaddresses() now handles Header objects (GH-13797) #27242 [3.9] bpo-27513: email.utils.getaddresses() now handles Header objects (GH-13797) #27245
Files	iso-8859-1-encoded-from-header.mail: test mail decode_from_header.py: test program, that demonstrates the problem

^{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 2021-07-19.16:55:54.871>
created_at = <Date 2016-07-14.10:50:10.937>
labels = ['type-bug', 'expert-email', '3.10', '3.11']
title = 'email.utils.getaddresses does not handle Header objects'
updated_at = <Date 2021-07-19.17:28:59.779>
user = 'https://bugs.python.org/frispete'

bugs.python.org fields:

activity = <Date 2021-07-19.17:28:59.779>
actor = 'lukasz.langa'
assignee = 'none'
closed = True
closed_date = <Date 2021-07-19.16:55:54.871>
closer = 'lukasz.langa'
components = ['email']
creation = <Date 2016-07-14.10:50:10.937>
creator = 'frispete'
dependencies = []
files = ['43714', '43715']
hgrepos = []
issue_num = 27513
keywords = ['patch']
message_count = 6.0
messages = ['270399', '270401', '270425', '397812', '397815', '397820']
nosy_count = 8.0
nosy_names = ['barry', 'frispete', 'r.david.murray', 'lukasz.langa', 'ZackerySpytz', 'miss-islington', 'xtreak', 'Jeffrey.Kintscher']
pr_nums = ['13797', '27242', '27245']
priority = 'normal'
resolution = 'fixed'
stage = 'resolved'
status = 'closed'
superseder = None
type = 'behavior'
url = 'https://bugs.python.org/issue27513'
versions = ['Python 3.10', 'Python 3.11']

[frispete]

An unfortunate combination of get_all and getaddresses results in a Traceback:

Traceback (most recent call last):
  File "misc/decode_from_header.py", line 17, in <module>
    print('From: %s' % email.utils.getaddresses(val))
  File "/usr/lib64/python3.4/email/utils.py", line 112, in getaddresses
    all = COMMASPACE.join(fieldvalues)
TypeError: sequence item 0: expected str instance, Header found

Here's the relevant part of it:
Content-type: text/html;charset=iso-8859-1
From: Itaú Uniclass. <comunicado.com.br@atendimento.gotdns.ch>

Obviously, the From header is iso-8859-1 encoded as well, and violates RFC 2822 as such. But making it crash in the usual combination of

    val = msg.get('from')
    email.utils.getaddresses([val])

isn't the real McCoy either..

[frispete]

message.get cannot decode the header correctly, and returns a Header instance instead, which makes email.utils.getaddresses stumble upon...

A much better behavior for getaddresses in this case would be returning the perfectly valid address, and ignoring the invalid dtext part.

[bitdancer]

This appears to be something that was overlooked when btyes support was added in 3.2. getaddresses should indeed be able to handle a Header object if handed one.

[ambv]

New changeset 89f4c34 by Zackery Spytz in branch 'main':
bpo-27513: email.utils.getaddresses() now handles Header objects (bpo-13797)
89f4c34

[ambv]

New changeset 8c43bf1 by Miss Islington (bot) in branch '3.10':
bpo-27513: email.utils.getaddresses() now handles Header objects (GH-13797) (GH-27242)
8c43bf1