Re: Removing unloaded functions from auto-mode-alist.

[Lute Kamstra <Lute.Kamstra.lists@xs4all.nl>]

Stefan Monnier <monnier@iro.umontreal.ca> writes:

[...]

> if I have function FOO autoloaded and (require 'blabla) replaces
> that with some other definition, than an immediately following
> (unload-feature 'blabla) should restore the autoload, no matter
> whether the autoload was pointing to blabla.el or not.

I have thought about this some more and there's more to it than just
autoloads.

What currently happens when you do (require 'blabla) and then
(unload-feature 'blabla) is that all functions that "blabla" defined
are unbound.  Maybe not the right thing to do, but quite consistent.

(There is only one case where (unload-feature 'blabla) will do
anything else then fmakunbound a function that "blabla" defined and
that is when a function was autoloaded and that function was defined
when do_autoload loaded "blabla".)

Consider the following situation:

function 'a is autoloaded: (autoload "blabla" ...).
function 'b is autoloaded: (autoload "other" ...).
function 'c is defined.
function 'd is unbound.

"blabla" defines 'a, 'b, 'c, and 'd as functions.

Do (require 'blabla) and then (unload-feature 'blabla).

Currently, all four functions will be unbound by unload-feature.  You
propose to let unload-feature restore both 'a and 'b to their previous
autoloads [1].  But what should be done with 'c?

I think restoring 'c to its previous definition would be the right
thing to do.  But that would be quite a substantial change.  It's
probably best to leave this alone until after the release.

Lute.



[1] I have actually implemented this for Frequire; it's quite simple:

Index: src/fns.c
===================================================================
RCS file: /cvsroot/emacs/emacs/src/fns.c,v
retrieving revision 1.389
diff -c -r1.389 fns.c
*** src/fns.c	22 Apr 2005 07:11:08 -0000	1.389
--- src/fns.c	24 Apr 2005 20:06:44 -0000
***************
*** 3482,3487 ****
--- 3482,3488 ----
  
    if (NILP (tem))
      {
+       Lisp_Object first, second;
        int count = SPECPDL_INDEX ();
        int nesting = 0;
  
***************
*** 3528,3533 ****
--- 3529,3551 ----
  	error ("Required feature `%s' was not provided",
  	       SDATA (SYMBOL_NAME (feature)));
  
+       /* Save the old autoloads, in case we ever do an unload.  */
+       tem = Vautoload_queue;
+       while (CONSP (tem))
+ 	{
+ 	  first = XCAR (tem);
+ 	  second = Fcdr (first);
+ 	  first = Fcar (first);
+ 	  
+ 	  /* Note: This test is subtle.  The cdr of an autoload-queue entry
+ 	     may be an atom if the autoload entry was generated by a defalias
+ 	     or fset.  */
+ 	  if (CONSP (second))
+ 	    Fput (first, Qautoload, (XCDR (second)));
+ 
+ 	  tem = XCDR (tem);
+ 	}
+ 
        /* Once loading finishes, don't undo it.  */
        Vautoload_queue = Qt;
        feature = unbind_to (count, feature);