Toio little error information from widgets

Toio little error information from widgets

[Lennart Borgman (gmail)]

The following code has an error. This error is however very hard to 
detect. I do not get a traceback, it just behaves very strange.

Try the following:

   emacs -Q
   (eval the code below)
   M-x customize-option RET temp-cust2 RET

Then click INS. It does not work as I expect. (To get it working 
uncomment the line

   ;;(or (eq value 'fundamental-mode)

and the corresponding ")" in the code.

What could be done about this?

Here is the code:

(defun major-modep(value)
   (let ((sym-name (symbol-name value)))
     ;; Do some reasonable test to find out if it is a major mode.
     ;; Load autoloaded mode functions.
     ;;
     ;; Fix-me: Maybe test for minor modes? How was that done?
     (when (and (fboundp value)
                (< 5 (length sym-name))
                (string= "-mode" (substring sym-name (- (length 
sym-name) 5)))
                (if (and (listp (symbol-function value))
                         (eq 'autoload (car (symbol-function value))))
                    (progn
                      (message "loading ")
                      (load (cadr (symbol-function value)) t t))
                  t)
                ;;(or (eq value 'fundamental-mode)
                    (intern-soft (concat sym-name "-hook"))
                    (boundp (intern-soft (concat sym-name "-hook"))))
                ;;)
       t)))

(define-widget 'major-mode-function2 'function
   "A major mode lisp function."
   :complete-function (lambda ()
		       (interactive)
		       (lisp-complete-symbol 'major-modep))
   :prompt-match 'major-modep
   :prompt-history 'widget-function-prompt-value-history
   :match-alternatives '(major-modep)
   :validate (lambda (widget)
	      (unless (major-modep (widget-value widget))
		(widget-put widget :error (format "Invalid function: %S"
						  (widget-value widget)))
		widget))
   :value 'fundamental-mode
   :tag "Major mode function")

(defcustom temp-cust2 nil
   "doc"
   :type '(alist :key-type major-mode-function2
                 :value-type (set
                              (list :tag "Highlighting on" (const hion) 
boolean)
                              (list :tag "Highlighting" (const hili) 
function)
                              (list :tag "Goto" (const goto) function)
                              (list :tag "Next" (const next) function)
                              (list :tag "Prev" (const next) function)
                              )))

Re: Toio little error information from widgets

[Daniel Brockman]

"Lennart Borgman (gmail)" <lennart.borgman@gmail.com> writes:

>                ;;(or (eq value 'fundamental-mode)
>                    (intern-soft (concat sym-name "-hook"))
>                    (boundp (intern-soft (concat sym-name "-hook"))))
>                ;;)

This part does not make sense:

    (or (intern-soft (concat sym-name "-hook"))
        (boundp (intern-soft (boncat sym-name "-hook"))))

In general, nothing that looks like this can make sense,

    (or FOO (boundp FOO))

because `boundp' will only ever be called if FOO is nil.

-- 
Daniel Brockman <daniel@brockman.se>

Re: Toio little error information from widgets

[Lennart Borgman (gmail)]

Daniel Brockman wrote:
> "Lennart Borgman (gmail)" <lennart.borgman@gmail.com> writes:
> 
>>                ;;(or (eq value 'fundamental-mode)
>>                    (intern-soft (concat sym-name "-hook"))
>>                    (boundp (intern-soft (concat sym-name "-hook"))))
>>                ;;)
> 
> This part does not make sense:
> 
>     (or (intern-soft (concat sym-name "-hook"))
>         (boundp (intern-soft (boncat sym-name "-hook"))))
> 
> In general, nothing that looks like this can make sense,
> 
>     (or FOO (boundp FOO))
> 
> because `boundp' will only ever be called if FOO is nil.
> 

Thamnks. Sorry, I just added the "fundamental-mode" line to make it more 
clear when I posted. I  missed to put and "add" around the following two 
lines.

It should be
                ;;(or (eq value 'fundamental-mode)
                ;; (and
                    (intern-soft (concat sym-name "-hook"))
                    (boundp (intern-soft (concat sym-name "-hook"))))
                ;;))

Both the "fundamental-line" and the "and" line must be uncommented to 
get it working.

Re: Toio little error information from widgets

[Lennart Borgman (gmail)]

Lennart Borgman (gmail) wrote:
> Daniel Brockman wrote:
>> "Lennart Borgman (gmail)" <lennart.borgman@gmail.com> writes:
>>
>>>                ;;(or (eq value 'fundamental-mode)
>>>                    (intern-soft (concat sym-name "-hook"))
>>>                    (boundp (intern-soft (concat sym-name "-hook"))))
>>>                ;;)
>>
>> This part does not make sense:
>>
>>     (or (intern-soft (concat sym-name "-hook"))
>>         (boundp (intern-soft (boncat sym-name "-hook"))))
>>
>> In general, nothing that looks like this can make sense,
>>
>>     (or FOO (boundp FOO))
>>
>> because `boundp' will only ever be called if FOO is nil.
>>
> 
> Thamnks. Sorry, I just added the "fundamental-mode" line to make it more 
> clear when I posted. I  missed to put and "add" around the following two 
> lines.
> 
> It should be
>                ;;(or (eq value 'fundamental-mode)
>                ;; (and
>                    (intern-soft (concat sym-name "-hook"))
>                    (boundp (intern-soft (concat sym-name "-hook"))))
>                ;;))
> 
> Both the "fundamental-line" and the "and" line must be uncommented to 
> get it working.


I looked a little bit further. The error (which a bit surprisingly is 
"End of file during parsing") happens in `widget-apply' which is called 
from `widget-insert-button-action'.

`widget-apply' internally calls Fapply, which is `apply'.

The message buffer contains

   Debug on Error enabled globally
   End of file during parsing
   Back to top level.

There is no problem just calling a function which gets an error during 
apply, something like this

  (defun temp-bad-div(x)
    (interactive "nNumber: ")
    (message "%s" (apply '/ 100 (list x))))

This gives the trace-back I expect if called with x=0.

`widget-apply' is very short and the crucial part looks like

   GCPRO2 (newargs[0], newargs[2]);
   result = Fapply (3, newargs);
   UNGCPRO;

However i have not much idea about what GCPRO2 does so maybe someone who 
knows that can look a bit further? Why does not the trace-back appear here?