Infinite loop in `email._header_value_parser._fold_mime_parameters` when parameter names are too long

Bug report

Bug description:

Tested with 3.6 and 3.13.1

>>> import email.message
>>> message = email.message.EmailMessage()
...
>>> message.add_attachment('Hello World!', filename='hello.txt', params={130 * 'A': 'too long parameter name'})
None
>>> message.defects
[]
>>> message
<email.message.EmailMessage object at 0x7fe78ec74ec0>
>>> message.as_string()

130 characters for a media type parameter name is (a bit) more than https://datatracker.ietf.org/doc/html/rfc6838#section-4.3 allows but I didn't expect it to lead into an infinite loop. I wanted to check if the email module would catch that defect, which apparently it doesn't.

Distribution is openSUSE Leap 15.6, python 3.13.1 was installed from pyenv, 3.6 is from the distribution. The python3.11 binary from the distribution exhibits the same behaviour.

CPython versions tested on:

3.13

Operating systems tested on:

Linux

Linked PRs

• gh-138226
• gh-138227
• gh-138231

Reproduisez le problème avec email.message.EmailMessage.add_attachment et un nom de paramètre de 130 caractères, puis examinez email._header_value_parser._fold_mime_parameters. Consultez la discussion sur l’issue associée et les PRs liés avant de poursuivre. Le travail est terminé lorsque l’entrée ne boucle plus indéfiniment et que la couverture de régression vérifie le comportement obtenu.