`UnboundLocalError` in `email.message.Message.get_payload`

[thib-d]

Bug report

Bug description:

    html_body = part.get_payload(decode=True).decode()
  File "/usr/local/lib/python3.8/email/message.py", line 282, in get_payload
    return quopri.decodestring(bpayload)

CPython versions tested on:

CPython main branch

Operating systems tested on:

Linux

Linked PRs

• gh-134759: UnboundLocalError in email.message.Message.get_payload #136071

[picnixz]

The error is here:

cpython/Lib/email/message.py

Lines 316 to 317 in 96905bd

	if cte == 'quoted-printable':
	return quopri.decodestring(bpayload)

cc @bitdancer

[makridenko]

hi, can i work on this?

[skv0zsneg]

Hello! I would like to work on it but did not work with CPython at all. Will it be a problem? If not where I should start with?

[sobolevn]

Hi, @skv0zsneg and @makridenko! Thanks a lot for your interest.

@makridenko since you were first, you can surely work on this. Because it looks like that no one else has started yet.

@skv0zsneg we value new contributors, please, don't feel left out :) You can pick any other issue from the opened ones 🤝

[skv0zsneg]

Hey everyone!

Trying to reproduce this bug UnboundLocalError but it want falling.

What I'm doing in REPL:

>>> raw_email = """Content-Type: text/plain; charset="utf-8"
... Content-Transfer-Encoding: quoted-printable
... 
... Hey!"""
>>> from email import message_from_string
>>> msg = message_from_string(raw_email)
>>> msg.get_payload(decode=True).decode()
'Hey!'
>>> msg._headers
[('Content-Type', 'text/plain; charset="utf-8"'), ('Content-Transfer-Encoding', 'quoted-printable')]

As mentioned by @picnixz, the error must be on line 317. To get here I use email message with quoted-printable encoding and body message surely get into quopri.decodestring but (luckly?) it does not fall. Am I miss something?

OS: Linux (Ubuntu 24.04.2 LTS)
Python: Python 3.15.0a0

[picnixz]

The "bad" code path is only taken when payload is not a string, cte == 'quoted-printable' and decode is True. Considering there is

        if i is not None and not isinstance(self._payload, list):

We can't just use a list because if is_multipart() would return true and we would early exit. So we need to use a bytes payload with decode = True (I think).