Re: Interesting problem: eval-after-load and local variables

[Kevin Rodgers]

On 10/16/12 2:02 AM, Sebastien Vauban wrote:
> In order to speed up my Emacs startup, I've put many customizations in
> eval-after-load's, such as:
>
> --8<---------------cut here---------------start------------->8---
>    (eval-after-load "time-stamp"
>      '(progn
>         ;; format of the string inserted by `M-x time-stamp'
>         (setq time-stamp-format "%:y-%02m-%02d %3a %02H:%02M %u")))
> --8<---------------cut here---------------end--------------->8---
>
> in order to avoid the require itself in the .emacs file.

In general, it is not necessary to load a library before customizing its global
options.  You should get the desired effect with just:

(setq time-stamp-format "%:y-%02m-%02d %3a %02H:%02M %u")

> Now, this causes a problem, as my local variable customizations aren't
> respected anymore.
>
> For example, I have the following local vars in my file `common.sty' to set up
> the format of the time-stamp (à la LaTeX):
>
> --8<---------------cut here---------------start------------->8---
> %% common.sty -- LaTeX common commands and environments
>
> \NeedsTeXFormat{LaTeX2e}
> \ProvidesPackage{common}[2012/10/15 v1.0 Common stuff between documents and 
> presentations]
>
> % ...
>
> %% End of package
> \endinput % very last line
>
> % Local Variables:
> % time-stamp-format: "%:y/%02m/%02d"
> % time-stamp-start: "Provides\\(Class\\|Package\\){[a-zA-Z-]+}\\["
> % time-stamp-end: " "
> % End:
> --8<---------------cut here---------------end--------------->8---
>
> The problem is the following:
>
> - Upon opening the file, Emacs sees it needs to load time-stamp.

I don't see how, since those variables aren't autoloaded.  (Their autoload
cookies only result in the safe-local-variable property being dumped into the
emacs executable for each symbol.)  I suspect you have enabled time stamp as
documented in the Emacs manual:

   Then add the hook function `time-stamp' to the hook
`before-save-hook'; that hook function will automatically update the
time stamp, inserting the current date and time when you save the file.

(The function time-stamp is autoloaded.)

> - It does it (via the predefined autoloads), but the eval-after-load overrides
>    the local variables' value.

Yes, because the eval-after-load form is apparently evaluated while the
common.sty buffer is current, and the file local variable section has already
made each variable local to that buffer.

> - When saving the file, the time-stamp format provided in local vars is NOT
>    applied.

Actually, I think the file local variables are applied and then overridden by
the eval-after-load form (but only for the first file that you save).  Do other
files with time stamp templates work as intended?

> In a way, that's perfectly normal. In another, not at all: I would expect the
> local vars to win over the wide values, in any configuration (even if my setq
> were in an eval-after-load construct).
>
> What do you think?

I think you should either skip the eval-after-load boilerplate, or use
setq-default in the eval-after-load form as suggested by Michael.

--
Kevin Rodgers
Denver, Colorado, USA