Re: /srv/bzr/emacs/trunk r100059: (bug-reference-url-format): Mark as `safe-local-variable' if the value

[Davis Herring]

> (put 'bug-reference-url-format 'safe-local-variable
>   (let ((f (get 'bug-reference-url-format 'safe-local-variable)))
>    (lambda (s) (or (funcall f s) (eq s
> 'clisp-bug-reference-url-format)))))

That won't work if the existing value is not a function (e.g. if it is t
(which would be foolish, of course) or nil).  Moreover, you need to use
backquotes: (let ((f ...)) `(lambda (s) (or (funcall ,f s) ...))) (this is
one of the reasons people want lexbind).

> so that if others do that too, I will not override them.
> in fact, maybe the above should be a standard function
> (add-safe-value variable symbol)

I don't know how often it is useful to be able to add many individual safe
values for a variable; perhaps instead there should be another variable
whose file-local value can be a string s from which
`bug-reference-url-format' is calculated as (intern (concat s
"-url-format")).  Then only functions intended for the purpose could be
selected by the file.

Or, more generally, perhaps there should be a symbol property
`safe-file-function' placed on symbols whose values as functions were safe
to call regardless of context, so that we could then allow precisely those
symbols as the values of certain function-valued file locals:

(put 'clisp-bug-reference-url-format 'safe-file-function t)
(defun safe-file-function-p (f)
  (and (symbolp f) (get f 'safe-file-function))
(put 'bug-reference-url-format 'safe-local-variable 'safe-file-function-p)

Davis

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