Displaying errors during startup

Displaying errors during startup

[Lennart Borgman]

After the recent discussion about error messages at startup (this time 
it was about pure-space-overflow) it came to my mind I often tend to 
miss errors at startup. You can not see them because of the splash 
screen for example. I just started testing `lwarn' because of this. I 
did something like this:

    (condition-case err
        (require 'something-bad)
      (error
       (lwarn '(.emacs) :error "%s" (error-message-string err))))

This displays the error in a nice way even during startup. Looking a bit 
closer at it it seems to be some trouble with using `pop-to-buffer' in 
startup.el when loading .emacs. I therefore suggest using 
`display-buffer' instead like lwarn does. It would also be nice to have 
a more visible face when putting this in the message buffer. I therefore 
suggest using something like the code below in startup.el (around line 905):

  (if init-file-debug
      (load inner)
    (condition-case error
        (load inner)
      (error
       (let ((message-log-max nil))
         (save-excursion
           (set-buffer (get-buffer-create "*Messages*"))
           (let ((s
                  (concat
                   "\n\n"
                   (format "An error has occurred while loading `%s':\n\n"
                           user-init-file)
                   (format "%s%s%s"
                           (get (car error) 'error-message)
                           (if (cdr error) ": " "")
                           (mapconcat (lambda (s) (prin1-to-string s t)) 
(cdr error) ", "))
                   "\n\n"
                   "To ensure normal operation, you should investigate 
and remove the\n"
                   "cause of the error in your initialization file.  
Start Emacs with\n"
                   "the `--debug-init' option to view a complete error 
backtrace.\n\n")))
             (put-text-property
              0 (length s)
              'face 'font-lock-warning-face
              s)
             (insert s)
             (insert "\n") ;; Needed to get normal face again.
             (message "Error in init file: %s%s%s"
                      (get (car error) 'error-message)
                      (if (cdr error) ": " "")
                      (mapconcat 'prin1-to-string (cdr error) ", "))
             ;;(let ((pop-up-windows nil))
             ;;  (pop-to-buffer "*Messages*"))
             (display-buffer "*Messages*") ;; display-buffer does the job.
             (sit-for 10) ;; sit-for is necessary to display the info at 
once.
             (setq init-file-had-error t)))))))

Maybe this would be good to do before the release because it makes it 
somewhat easier to trap errors.

Re: Displaying errors during startup

[Kevin Rodgers]

Lennart Borgman wrote:
> After the recent discussion about error messages at startup (this time 
> it was about pure-space-overflow) it came to my mind I often tend to 
> miss errors at startup. You can not see them because of the splash 
> screen for example. I just started testing `lwarn' because of this. I 
> did something like this:
> 
>    (condition-case err
>        (require 'something-bad)
>      (error
>       (lwarn '(.emacs) :error "%s" (error-message-string err))))

I wasn't aware of lwarn, so I checked it's doc string and found a
really minor error: the first period in the description of the
TYPE argument should either be deleted or replaced by a comma:

,----[ C-h f lwarn RET ]
| lwarn is an autoloaded Lisp function in `warnings'.
| (lwarn TYPE LEVEL MESSAGE &rest ARGS)
|
| Display a warning message made from (format MESSAGE ARGS...).
| Aside from generating the message with `format',
| this is equivalent to `display-warning'.
|
| TYPE is the warning type: either a custom group name (a symbol).
| or a list of symbols whose first element is a custom group name.
| (The rest of the symbols represent subcategories and
| can be whatever you like.)
|
| LEVEL should be either :debug, :warning, :error, or :emergency
| (but see `warning-minimum-level' and `warning-minimum-log-level').
|
| :emergency -- a problem that will seriously impair Emacs operation soon
| 	      if you do not attend to it promptly.
| :error     -- invalid data or circumstances.
| :warning   -- suspicious data or circumstances.
| :debug     -- info for debugging only.
|
| [back]
`----

-- 
Kevin Rodgers
Sr. Software Engineer, IHS

Re: Displaying errors during startup

[Richard Stallman]

Your idea seems like a good one, but

		 ;;(let ((pop-up-windows nil))
		 ;;  (pop-to-buffer "*Messages*"))
		 (display-buffer "*Messages*") ;; display-buffer does the job.
		 (sit-for 10) ;; sit-for is necessary to display the info at 
    once.

if the idea is to display both buffers, why is the sit-for needed?

Re: Displaying errors during startup

[Lennart Borgman]

Richard Stallman wrote:
> Your idea seems like a good one, but
>
> 		 ;;(let ((pop-up-windows nil))
> 		 ;;  (pop-to-buffer "*Messages*"))
> 		 (display-buffer "*Messages*") ;; display-buffer does the job.
> 		 (sit-for 10) ;; sit-for is necessary to display the info at 
>     once.
>
> if the idea is to display both buffers, why is the sit-for needed?
>   
Only a (sit-for 0) is necessary to update the screen I believe.