Re: Failing to advice `require'

[Barry Margolin]

In article <80r4r18ttc.fsf@somewhere.org>,
 "Sebastien Vauban" <wxhgmqzgwmuf@spammotel.com> wrote:

> Hello,
> 
> I tried to advice the require function, in order to get:
> 
> - performance information (load time)
> - call graph of `require'
> 
> with the following code:
> 
> --8<---------------cut here---------------start------------->8---
>   (defvar my/require-depth 0)
> 
>   (defadvice require (around require-around activate)
>     "Leave a trace of packages being loaded."
>     (let ((feature (ad-get-arg 0))
>           (filename (ad-get-arg 1))
>           (noerror (ad-get-arg 2))

You never use filename or noerror, why do you bother binding them?

>           (prefix (concat (make-string (* 2 my/require-depth) ? ) "+-> ")))
>       (setq my/require-depth (1+ my/require-depth))

You should bind my/require-depth in your 'let'. Then you don't need to 
restore it at the end, it will happen automatically (including if 
there's an error that aborts out).

>       (cond ((featurep feature)
>              (message "(info) %sRequiring `%s'... already loaded"
>                       prefix feature)
>              )
>             (t
>              (let ((my/time-start))
>                (message "(info) %sRequiring `%s'..." prefix feature)
>                (setq my/time-start (float-time))
>                ad-do-it
>                (message "(info) %sRequiring `%s'... %s (loaded in %.2f s)"
>                         prefix feature
>                         (locate-library (symbol-name feature))
>                         (- (float-time) my/time-start))
>                )))
>       (setq my/require-depth (1- my/require-depth))))
> --8<---------------cut here---------------end--------------->8---

> 
> It works quite well, except for the following case:
> 
> --8<---------------cut here---------------start------------->8---
> ;; Requiring `auth-source'...
> ;; (info)  +-> Requiring `password-cache'... 
> d:/home/sva/Downloads/emacs/site-lisp/gnus/lisp/password-cache.elc (loaded in 
> 0.11 s)
> ;; (info)  +-> Requiring `mm-util'... already loaded
> ;; (info)  +-> Requiring `gnus-util'... already loaded
> ;; (info)  +-> Requiring `eieio'... already loaded [2 times]
> ;; byte-code: eieio not found in `load-path' or gnus-fallback-lib/ directory.
> --8<---------------cut here---------------end--------------->8---
> 
> Guess what? `eieio' is in my default load path, in my GNU Emacs 24.1.1
> (i386-mingw-nt5.1.2600) of 2012-06-02 on MARVIN on Windows XP.
> 
> Do you have any idea why it's failing?

The real require returns the feature name, or nil if the package is not 
found and noerror is set, yours returns various other things. You need 
to ensure that you return the correct thing; 'prog1' is useful for this:

(prog1 ad-do-it
       (message ...))

-- 
Barry Margolin, barmar@alum.mit.edu
Arlington, MA
*** PLEASE post questions in newsgroups, not directly to me ***