Subject: bug#18096: 24.3.92; async shell command and a busy buffer leads to error

From: Juri Linkov <[email-masked]>
Date: Mon, 28 Jul 2014 02:53:00 +0300

> --- a/lisp/simple.el
> +++ b/lisp/simple.el
> @@ -2904,7 +2904,8 @@ the use of a shell (with its need to quote arguments)."
>  		      (error "Shell command in progress")))
>  		   ((eq async-shell-command-buffer 'confirm-new-buffer)
>  		    ;; If will create a new buffer, query first.
> -		    (if (yes-or-no-p "A command is running in the default buffer.  Use a new buffer? ")
> +		    (if (and (stringp output-buffer)
> +                             (yes-or-no-p "A command is running in the default buffer.  Use a new buffer? "))
>  			(setq buffer (generate-new-buffer
>  				      (or output-buffer "*Async Shell Command*")))
>  		      (error "Shell command in progress")))

This will ignore the user customization in `async-shell-command-buffer'
if the user want it to ask a question whether to create a new buffer.
More tolerating would be trying to get a new buffer name even when
the given argument is a buffer:

=== modified file 'lisp/simple.el'
--- lisp/simple.el	2014-07-08 08:27:45 +0000
+++ lisp/simple.el	2014-07-27 23:44:20 +0000
@@ -2986,12 +2986,14 @@ (defun shell-command (command &optional
 		    ;; If will create a new buffer, query first.
 		    (if (yes-or-no-p "A command is running in the default buffer.  Use a new buffer? ")
 			(setq buffer (generate-new-buffer
-				      (or output-buffer "*Async Shell Command*")))
+				      (or (and (bufferp output-buffer) (buffer-name output-buffer))
+					  output-buffer "*Async Shell Command*")))
 		      (error "Shell command in progress")))
 		   ((eq async-shell-command-buffer 'new-buffer)
 		    ;; It will create a new buffer.
 		    (setq buffer (generate-new-buffer
-				  (or output-buffer "*Async Shell Command*"))))
+				  (or (and (bufferp output-buffer) (buffer-name output-buffer))
+				      output-buffer "*Async Shell Command*"))))
 		   ((eq async-shell-command-buffer 'confirm-rename-buffer)
 		    ;; If will rename the buffer, query first.
 		    (if (yes-or-no-p "A command is running in the default buffer.  Rename it? ")