Re: using flet to suppress meta generation in html export?

[Matt Price <moptop99@gmail.com>]

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AH, THISI S SUPER-HELPFUL, aARON. MANY THANK.  i'M HOPING THAT BY THE TIME
i RETIRE i WILL BEGIN TO UNDERSTAND LEXICAL SCOPING IN LISP...


On Tue, Nov 6, 2018 at 10:35 AM Aaron Ecay <aaronecay@gmail.com> wrote:

> Hi Matt,
>
> 2018ko azaroak 6an, Matt Price-ek idatzi zuen:
> >
> > Hi,
> >
> > I was writing a function to quickly post the ocntents of subtrees to the
> > Canvas Learning Management System.  I was trying to strip down the
> exported
> > HTML to an absolute minimum and had forgotten about the body-only
> paramter
> > to org-export-as (!!). So, my solution was to try to rebind
> > 'org-html--build-meta-info to always just return "".   However, I can't
> > seem to do it properly and I'm wondering if someone can help me figure
> out
> > what's wrong. It's my first time using cl-flet! And I know there are
> > various approaches, but I odn't understnad whyt this is notworking, when
> > for instance, this does work for me:
> >
> > (cl-flet ((+
> >            (lambda (&rest args) (message "no plus!"))))
> >   (+ "whoops"))
> > ;; "no plus!"
> >
> > Meanwhile, here's my  non-functional code:
>
> Quoting from the info page (info "(cl) Function Bindings"):
>
>      The bindings are lexical in scope.  This means that all references
>      to the named functions must appear physically within FORMS.
>
> I believe that you can accomplish what you are trying to do with:
>
> (cl-letf (((symbol-function 'org-html--build-meta-info)
>            (lambda (&rest args) "")))
>   your-code-here)
>
> You could also do something like:
>
> (let ((my-advice (lambda (&rest _) "")))
>   (advice-add 'org-html--build-meta-info :override my-advice)
>   (unwind-protect
>       (progn
>         your-code-here)
>     (advice-remove 'org-html--build-meta-info my-advice)))
>
> (Why do I think this is better, despite being more verbose?  Advice-add
> is specifically designed to change the binding of functions at runtime,
> and so it does some specialized things that cl-letf doesnʼt do.  This in
> turn means that it should be a more robust way of accomplishing the
> desired outcome.)
>
> --
> Aaron Ecay
>

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