23.0.50; catching C-x 3 in yes-or-no-p

23.0.50; catching C-x 3 in yes-or-no-p

[Lennart Borgman (gmail)]

The error raised when doing C-x 3 when yes-or-no-p is active can not be 
handled.

To see this start from

    emacs -Q

and eval this function in the *scratch* buffer

   (defun protected-yes-or-no-p ()
     (condition-case err
         (yes-or-no-p "Prompt ")
       (error
       (lwarn 'got-error :warning "%s" err))))

and call it. When the prompt is visible type

   C-x 3


In GNU Emacs 23.0.50.1 (i386-mingw-nt5.1.2600)
  of 2008-01-13

Re: 23.0.50; catching C-x 3 in yes-or-no-p

[Richard Stallman]

    and eval this function in the *scratch* buffer

       (defun protected-yes-or-no-p ()
	 (condition-case err
	     (yes-or-no-p "Prompt ")
	   (error
	   (lwarn 'got-error :warning "%s" err))))

    and call it. When the prompt is visible type

       C-x 3

I think I figured out what happened.
I suspect that you called it with M-:, right?
That binds debug-on-error to t.

yes-or-no-p starts a recursive editing loop, and when there are no
handlers _inside_ the recursive editing loop and debug-on-error is t,
errors invoke the debugger.  So this error invokes the debugger.

I think that qualifies as a bug.  Perhaps the right fix is that
recursive editin levels should bind debug-on-error to nil.
Does anyone see a problem in that fix?