bug#69738: [BUG] rmail-mail-new-frame doesn't delete the new frame after composing the message on Emacs 29.2

[Eli Zaretskii]

> Date: Mon, 11 Mar 2024 22:49:54 +0000
> From: rameiko87@posteo.net
> 
> For brevity I don't include the steps for C-c nor for C-s but only for 
> C-d and C-k; but I can assure you that the case of C-c would yield the 
> same result; I wonder what the desired result would be for C-s instead.
> 
> Steps to reproduce:
> 
> emacs -Q -nw
> M-: (setq rmail-mail-new-frame t)
> M-x rmail
> m
> C-c C-d
> 
> alternatively, use C-c C-k on the last line.
> 
> Expected result:
> The frame is deleted (as the manual specifies at the end of 34.10).
> 
> Actual result:
> The frame is not deleted.

It's a documentation bug: that frame is deleted only if certain
conditions are met.  One of those conditions is that there are
visible frames on display besides the frame where the message was
composed.  In the -nw session, that condition is not met.  See
rmail-mail-return for more details about what is actually being done
in each case.

IOW: this is a feature, and (IMO) a reasonable one at that, it just
needs a better documentation.