Comment #5 on issue 31 by joaotavora: Executing lisp code after TAB
http://code.google.com/p/yasnippet/issues/detail?id=31

Won't take action on this enhancement issue until further feedback.

In issue 100 nearly the same task is discussed. Mine is different to
this because I want to call the function after i filled out a field
and reftex-label uses this filed as input. #100 calls the function
immediately after expansion.

I tried to combine your answer and the answer to #100, but it does not
work yet:

I try:

\section{${1:Titel der Tour?}}%
\index{${1:$(if (eq yas/moving-away-p t) (reftex-label nil 'dont-
insert))}}%

$1 is mirrored but reftex is not called. it jumpes directly to next
field.

Secondly I tried:

\section{${1:Titel der Tour?}}%
\index{$1}%
\index{${2:$$(if (eq yas/moving-away-p t) (reftex-label nil 'dont-
insert))}}%
%
$2 is only a dummy, I press TAB. reftex-label is called indeed,
suggests the label. I press enter to accept, but noting is inserted
and yas jumps to the next input field

Maybe you have another idea?

Thanks, Peter

On 5 Sep., 14:07, codesite-nore...@google.com wrote:

Mirror transformations are basically functions of the text (text or  
yas/text variable) that is present on the field they mirror. YASnippet  
wasn't designed to handle stuff such as side effects, which is one of  
the things that might make your intention work.

Consider the following *workaround*, check if it works

`(progn (setq my-reftex-cache nil) "")`
\section{${1:"Titel der Tour"$(if yas/moving-away-p
                    (progn (setq my-reftex-cache (reftex-label nil  
'dont-insert))
                           (yas/update-mirrors snippet))
                  (setq my-reftex-cache nil))}}%
\index{${1:$(or my-reftex-cache
                 "waiting...")}}%

The my-reftex-cache variable implements the side-effect communication  
between the field and the mirror. Then you need the first progn line  
to initialize the variable. Then you need a **really** dirty hack  
where you force a mirror update. This is not guaranteed to work in the  
future (or in the present, for that matter), since it uses internal  
yasnippet workings which might change in the future.

But I ask you if you'd rather not use this:

\section{${1:"Titel der Tour"}}%
\index{${2:"waiting..."$(unless yas/modified-p (reftex-label nil 'dont-
insert))}}%

The only *inconvenient * here is that you get a chance to change the  
value inserted by reftex-label. Other than that, it's much cleaner,  
and is the "recommended" way.

Naturally, I didn't think of your scenario when I designed this  
feature. Its possible to make the first alternative cleaner in the  
future, I'll leave the issue open, maybe retitle it.

Comment #6 on issue 31 by joaotavora: Executing lisp code after TAB
http://code.google.com/p/yasnippet/issues/detail?id=31

See thread  
http://groups.google.com/group/smart-snippet/browse_thread/thread/282....

Additionally, the following snippet can help the drawback of the second  
alternative:

\section{${1:"Titel der Tour"}}%
\index{${2:"waiting..."$(unless yas/modified-p (prog1 (reftex-label  
nil 'dont-insert)

(yas/schedule-field-skip)))}}%
$0

and some supporting elisp code...

(defun yas/schedule-field-skip ()
   (add-hook 'post-command-hook 'yas/field-skip-once 'append 'local))

(defun yas/field-skip-once ()
   (condition-case err
       (yas/next-field)
     (error nil))
   (remove-hook 'post-command-hook 'yas/field-skip-once 'local))

thank you very much! I can now completely substitute msf abbrev with
yasnippet.

The version 2 works, and with the additional code it is perfect, the
same behaviour as in msf.

For the record: The snippet has to be slightly modified, because
reftex-label with parameter dont-insert does not write the \label{}.
So the complete snippet is:

\section{${1:Title}}%
\index{$1}%
\label{${2:"waiting..."$(unless yas/modified-p (prog1 (reftex-label
nil 'dont-insert)
(yas/schedule-field-skip)))}}%

On 13 Sep., 17:01, codesite-nore...@google.com wrote: