Re: Dealing with obsoletion warnings in non-core code

[Gregory Heytings via "Emacs development discussions." <emacs-devel@gnu.org>]

Hi Stefan,

I gave the two macros a better name, they are now:

(defmacro funcall-no-warn (fun &rest args) `(funcall (intern (symbol-name ,fun)) ,@args))
(defmacro set-no-warn (var val) `(set (intern (symbol-name ,var)) ,val))

and should be used as follows:

(if (fboundp 'new-function)
     (funcall-no-warn 'new-function arg ...)
   (funcall-no-warn 'old-function arg ...))

(if (boundp 'new-variable)
     (set-no-warn 'new-variable value)
   (set-no-warn 'old-variable value))

>
> That's just obfuscating the code
>

You probably meant: Indeed, that Just Works^TM, congratulations! ;-)

>
> (which will prevent the compiler from detecting some real errors such as 
> when you have a typo in the function's name or when you don't provide 
> the right number of args)
>

Indeed.  If there's another way to do this while detecting errors at 
compilation time, that would be even better.  OTOH, this will quickly 
raise a runtime error in case of typos or wrong number of arguments, which 
is unlikely to get unnoticed by the maintainer.  Of course I'm not 
advocating to use this everywhere.

>
> and might be defeated by compiler optimizations.
>

It might be, but AFAICS it is not.  I forgot to mention that I tested the 
above macros on Emacs 21, 22, 23, 24, 25, 26, 27 and 28.  As I said, it 
Just Works^TM.

>
> I think the OP's question was how to "do it right", rather than how to 
> work around the problem.
>

I don't know.  It's just my proposed solution.  OTOH, I don't see how he 
could "do it right" when his problem statement mentions that he wants to 
support old Emacs versions, which by definition nobody can improve 
anymore.

Your idea of of a database of replacements might work, but it has to be 
implemented, and for the use case the OP has in mind it will not be useful 
before Emacs 3X.

Gregory