On Mon, 21 Jul 2025 11:51:38 +0200 Manuel Giraud <manuel@ledu-giraud.fr> wrote:

> Manuel Giraud <manuel@ledu-giraud.fr> writes:
>
>> Hi,
>>
>>From a current build, I can't call `async-shell-command' anymore.  Here
>> is my recipe:
>>
>>   - emacs -Q
>>   - M-& ls <RET>
>>
>> I get the following error:
>>
>> shell-command: Asynchronous shell commands cannot output to current
>> buffer
>
> I'm not quite sure about the logic at play here but the following patch
> fixes my issue:
>
> diff --git a/lisp/simple.el b/lisp/simple.el
> index 88886de05c4..f7f059793ca 100644
> --- a/lisp/simple.el
> +++ b/lisp/simple.el
> @@ -4715,7 +4715,8 @@ shell-command
>  	;; Output goes in a separate buffer.
>  	(if (string-match "[ \t]*&[ \t]*\\'" command)
>  	    ;; Command ending with ampersand means asynchronous.
> -            (let* ((_ (or (bufferp output-buffer)
> +            (let* ((_ (or (null output-buffer)
> +                          (bufferp output-buffer)
>                            (stringp output-buffer)
>                            (error "Asynchronous shell commands cannot output to current buffer")))
>                     (buffer (get-buffer-create

The commit message of 852009b4f1c9, which added the bufferp and stringp
checks and the error message, says 'Improve error message for "C-u M-!
something &"'.  An alternative is to ignore the prefix argument when the
command is asynchronous, just like `async-shell-command' ignores the
prefix argument: