bug#70691: 30.0.50; [PATCH] Eshell's TERM env varible use eshell-term-name as default

[Jim Porter <jporterbugs@gmail.com>]

On 5/1/2024 5:15 AM, Eli Zaretskii wrote:
>> From: Lin Sun <sunlin7.mail@gmail.com>
>> Date: Wed, 1 May 2024 06:40:25 +0000
>>
>> Since emacs-29 the Eshell has been enhanced for the ansi-color a lot.
[snip]
>>
>> So we can safely export eshell's "TERM" with `eshell-term-name` to
>> support executables with colors.
>> I attached the patch, please help review it. Thanks.
> 
> The fact that we can safely do that does not yet mean we _should_ do
> it.  In my book, setting TERM is a user preference, more or less.
> IOW, this is a change in the default behavior.
> 
> Jim, WDYT?

Unfortunately, I don't think this is the right way to do things (or else 
I'm just not understanding some part of it). The docstring for 
'eshell-term-name' says, "Name to use for the TERM variable when running 
visual commands," and its value defaults to 'term-term-name'. For visual 
commands (which use term.el), the terminal can do a lot more than just 
setting colors, such as moving the cursor around. "Normal", non-visual 
Eshell can't do that, so I think using the same setting for $TERM would 
be wrong.

We could make Eshell set $TERM to "dumb-emacs-ansi", which should have 
the correct terminal settings. I believe that terminfo has been 
upstreamed into ncurses.

However, I think if you want colors, it's best to change 
'comint-terminfo-terminal' instead to "dumb-emacs-ansi" (and then Eshell 
will use that setting automatically). I *don't* think we should change 
'comint-terminfo-terminal' by default though; that would be pretty 
invasive. Maybe we could use the Customize interface to make selecting 
"dumb-emacs-ansi" a matter of just checking a box, instead of typing it 
out by hand?