mailbox Babyl support can't cope with messages that have no body

[jikamens]

Bug report

Bug description:

The Babyl message file format allows messages to have a header only, no body. In this case there is just a message header between the *** EOOH *** and ^_^L, with no blank lines at the end. The Python module crashes with an assertion failure when it encounters this. It even crashes if you add a blank line; you have to add two blank lines, one representing the separator between the header and the body, and one representing body content (i.e., it can't cope with an empty body), to make the assertion failure go away.

The module should allow a header-only message with no separator or body.

CPython versions tested on:

3.12

Operating systems tested on:

Linux

[serhiy-storchaka]

Thank you for your report @jikamens. Are you interesting in creating a PR? If not, I'll do this myself, but I want to ask you first.

BTW, do you have a reference to the Babyl message file format specification?

[jikamens]

Thank you for your report @jikamens. Are you interesting in creating a PR? If not, I'll do this myself, but I want to ask you first.

I will put it on my to-do list, but my to-do list is very long so I honestly can't say when I will get to it.

BTW, do you have a reference to the Babyl message file format specification?

I don't think there is a reference for the Babyl message file format. I looked and could not find one. I think the only reference is how Emacs interprets Babyl files. Having used Emacs Rmail (which uses Babyl files under the hood) for many years—though I don't anymore, which is why I was converting files and discovered this issue and the other one I filed—I'm pretty confident that I'm right about these two issues, because I know Emacs handled my Babyl files properly and they had both of these issues when I ran them through Python.

[serhiy-storchaka]

The closest to the specification that I found is:
https://home.cs.colorado.edu/~main/cs1300-old/emacs/etc/BABYL

But it is still not clear whether message can omit a body and a newline between headers and an empty body.