Re: Improving representation of EIEIO objects in backtraces/error messages

[Eric Ludlam <eric@siege-engine.com>]

On 12/29/2016 02:02 PM, Eric Abrahamsen wrote:
> I can't be the first one to be bitten by this...
>
> When developing using EIEIO objects, backtraces and edebug messages
> can be very difficult to use. In edebug, if you're lucky, you get the
> #<object-class I'm an object> representation, but if you're unlucky,
> you get the vector. In backtraces, you always get the vector.
>
> For large objects, or those involving recursive data structures, this
> makes error reporting frustrating, to put it delicately. It can take
> the printer a good couple seconds to barf up the representation of an
> object, and when it does it makes a huge mess of the minibuffer
> and/or *Message* buffer.

Hi Eric,

CEDET includes a 'data-debug' package.  If you enable that it provides a
way to navigate giant data structures as you might get with EIEIO.  It
is also a part of Emacs now, though I'm not that familiar with how it 
all was merged.

I have this in my .emacs file to take advantage of it:

(require 'data-debug)
(global-set-key "\M-:" 'data-debug-eval-expression)

I also include this for eieio:

(add-hook 'edebug-setup-hook
	  (lambda ()
	    (defalias 'edebug-prin1-to-string 'eieio-edebug-prin1-to-string)))

though I'm not sure if something equivalent is enabled by default during 
the EIEIO merge.

In the CEDET repository, you can get cedet-edebug.el.  It includes these 
two snippets that bind "A" to data debug.

;;;###autoload
(add-hook 'edebug-setup-hook
	  (lambda ()
	    (require 'cedet-edebug)
	    ;; I suspect this isn't the best way to do this, but when
	    ;; cust-print was used on my system all my objects
	    ;; appeared as "#1 =" which was not useful.  This allows
	    ;; edebug to print my objects in the nice way they were
	    ;; meant to with `object-print' and `class-name'
	    (defalias 'edebug-prin1-to-string 'cedet-edebug-prin1-to-string)
	    ;; Add a fancy binding into EDEBUG's keymap for ADEBUG.
	    (define-key edebug-mode-map "A" 'data-debug-edebug-expr)
	    ))

;;; DEBUG MODE TOO
;; This seems like as good a place as any to stick this hack.
;;;###autoload
(add-hook 'debugger-mode-hook
	  (lambda ()
	    (require 'cedet-edebug)
	    ;; Add a fancy binding into the debug mode map for ADEBUG.
	    (define-key debugger-mode-map "A" 'data-debug-edebug-expr)
	    ))


Eric