Subject: Re: bug#25270: eshell -- programmatically send input -- feature request

From: Jim Porter <[email-masked]>
Date: Sun, 15 May 2022 22:46:47 -0700

On 5/13/2022 7:02 AM, Lars Ingebrigtsen wrote:
> Keith David Bershatsky <[email-masked]> writes:
> 
>> As far as I am aware, users of eshell have been limited to sending
>> input programmatically by inserting the command into the eshell buffer
>> (at the command prompt) and then executing `eshell-send-input`.  Some
>> users (like myself) may feel that such a solution is lo-tech -- i.e.,
>> not very eloquent.
> 
> [...]
> 
>> The following is an example of how this new feature might be implemented:
>>
>> SAMPLE USAGE:  (eshell-send-input nil nil nil "ls -la /")
>>
>> (require 'eshell)
>>
>> (defun eshell-send-input (&optional use-region queue-p no-newline input-string-a)
> 
> (I'm going through old bug reports that unfortunately weren't resolved
> at the time.)
> 
> I think this makes sense, but I'm not very familiar with eshell
> internals, so I've added Jim to the CCs; perhaps he has some comments.

Hm, I think it's reasonable to have something similar to 
`comint-send-string' for Eshell, but I'm not quite sure what the best 
way to do this would be. I think a separate function, like 
`eshell-send-string', would probably be a nicer API, since it could be 
called like `comint-send-string'.

Also, for the code posted in the original message, I'm not sure the 
changes to `eshell-parse-command' are needed. It should already let you 
pass a command string to it. Maybe this is because there's an issue with 
how `eshell-parse-command' temporarily inserts COMMAND into the buffer 
(see the FIXME comment in the code in the original message)? If there 
is, we'd probably have to think quite a bit more about how to resolve it.

Some background: I think it would be pretty risky to try to perform 
Eshell argument parsing anywhere *but* in the contents of the current 
Eshell buffer, as in `eshell-parse-arguments--temp-buffer' in the 
original message. See `eshell-with-temp-command' in Emacs 29 (which is 
what the FIXME comment morphed into), in particular this part:

          ;; Since parsing relies partly on buffer-local state
          ;; (e.g. that of `eshell-parse-argument-hook'), we need to
          ;; perform the parsing in the Eshell buffer.

Basically, Eshell is extremely flexible, and argument parsing is handled 
by `eshell-parse-argument-hook', which can do all sorts of things to 
change how arguments are parsed, and may even be buffer-local to a 
particular Eshell instance. Parsing Eshell arguments anywhere but the 
"target" Eshell buffer is asking for trouble.

I'll see if I can put together a patch along the above line in the next 
couple weeks.