generated email message exceeds RFC-mandated limit of 998 characters

[ivyl]

BPO	40597
Nosy	@warsaw, @msapiro, @bitdancer, @maxking, @miss-islington, @ivyl
PRs	bpo-40597: email: Don't shy from using CTE for US-ASCII-only emails #20038 [3.8] bpo-40597: email: Use CTE if lines are longer than max_line_length consistently (gh-20038) #20084 bpo-40597: Allow email.contextmanager set_content() to set a null string. #20542 [3.9] bpo-40597: Allow email.contextmanager set_content() to set a null string. (GH-20542) #21404 [3.8] bpo-40597: Allow email.contextmanager set_content() to set a null string. (GH-20542) #21405

^{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 2020-07-09.00:18:35.262>
created_at = <Date 2020-05-11.19:00:19.898>
labels = ['type-bug', '3.8', 'expert-email', '3.9']
title = 'generated email message exceeds RFC-mandated limit of 998 characters'
updated_at = <Date 2020-07-09.00:19:01.131>
user = 'https://github.com/ivyl'

bugs.python.org fields:

activity = <Date 2020-07-09.00:19:01.131>
actor = 'maxking'
assignee = 'none'
closed = True
closed_date = <Date 2020-07-09.00:18:35.262>
closer = 'maxking'
components = ['email']
creation = <Date 2020-05-11.19:00:19.898>
creator = 'ivyl'
dependencies = []
files = []
hgrepos = []
issue_num = 40597
keywords = ['patch']
message_count = 11.0
messages = ['368641', '368646', '368810', '368811', '369157', '370395', '373350', '373353', '373354', '373362', '373363']
nosy_count = 6.0
nosy_names = ['barry', 'msapiro', 'r.david.murray', 'maxking', 'miss-islington', 'ivyl']
pr_nums = ['20038', '20084', '20542', '21404', '21405']
priority = 'normal'
resolution = 'fixed'
stage = 'resolved'
status = 'closed'
superseder = None
type = 'behavior'
url = 'https://bugs.python.org/issue40597'
versions = ['Python 3.8', 'Python 3.9']

[ivyl]

RFC53220 in section 2.1.1 mandates that the line cannot be longer than 998 characters and should not be longer than 78 characters (excluding CRLF). When we use raw_data_manager (default for EmailPolicy, EmailMessage) it does the correct thing as long as the message contains characters outside of 7bit US-ASCII set - base64 or qp Content-Transfer-Encoding which respects the line wrapping at 78 characters.

However if our message is limited the characters from the 7bit US-ASCII set no transfer encoding is applied, and such messages can easily go beyond 78 or even 998 characters.

[bitdancer]

The PR looks good to me, but I describe the change differently. I'm not sure how I missed this in the original implementation, since I obviously checked it for the 8bit case. Too long ago to remember :)

[bitdancer]

New changeset 6f2f475 by Arkadiusz Hiler in branch 'master':
bpo-40597: email: Use CTE if lines are longer than max_line_length consistently (gh-20038)
6f2f475

[bitdancer]

Thanks, Arkadiusz.