How should contextmanager/ContextDecorator work with generators?

GitHub fields:

assignee = None
closed_at = None
created_at = <Date 2019-08-01.23:33:04.730>
labels = ['3.8', 'docs']
title = 'How should contextmanager/ContextDecorator work with generators?'
updated_at = <Date 2019-09-03.10:21:10.928>
user = 'https://github.com/anntzer'

bugs.python.org fields:

activity = <Date 2019-09-03.10:21:10.928>
actor = 'Antony.Lee'
assignee = 'none'
closed = False
closed_date = None
closer = None
components = ['Documentation']
creation = <Date 2019-08-01.23:33:04.730>
creator = 'Antony.Lee'
dependencies = []
files = []
hgrepos = []
issue_num = 37743
keywords = []
message_count = 2.0
messages = ['348878', '351074']
nosy_count = 1.0
nosy_names = ['ncoghlan']
pr_nums = []
priority = 'normal'
resolution = None
stage = None
status = 'open'
superseder = None
type = None
url = 'https://bugs.python.org/issue37743'
versions = ['Python 3.8']