* How to reject visiting a file
@ 2014-12-12 1:46 Óscar Fuentes
2014-12-12 8:01 ` Eli Zaretskii
0 siblings, 1 reply; 7+ messages in thread
From: Óscar Fuentes @ 2014-12-12 1:46 UTC (permalink / raw
To: help-gnu-emacs
Is there a way to error-out when Emacs tries to visit certain file
before the file is loaded? I'll like to use a hook that receives the
file name and be able to throw an error from there that aborts the
operation.
^ permalink raw reply [flat|nested] 7+ messages in thread
* Re: How to reject visiting a file
2014-12-12 1:46 How to reject visiting a file Óscar Fuentes
@ 2014-12-12 8:01 ` Eli Zaretskii
2014-12-12 15:19 ` Óscar Fuentes
0 siblings, 1 reply; 7+ messages in thread
From: Eli Zaretskii @ 2014-12-12 8:01 UTC (permalink / raw
To: help-gnu-emacs
> From: Óscar Fuentes <ofv@wanadoo.es>
> Date: Fri, 12 Dec 2014 02:46:23 +0100
>
> Is there a way to error-out when Emacs tries to visit certain file
> before the file is loaded? I'll like to use a hook that receives the
> file name and be able to throw an error from there that aborts the
> operation.
You could define a file-handler for these files.
^ permalink raw reply [flat|nested] 7+ messages in thread
* Re: How to reject visiting a file
2014-12-12 8:01 ` Eli Zaretskii
@ 2014-12-12 15:19 ` Óscar Fuentes
2014-12-12 15:31 ` Stefan Monnier
0 siblings, 1 reply; 7+ messages in thread
From: Óscar Fuentes @ 2014-12-12 15:19 UTC (permalink / raw
To: help-gnu-emacs
Eli Zaretskii <eliz@gnu.org> writes:
>> Is there a way to error-out when Emacs tries to visit certain file
>> before the file is loaded? I'll like to use a hook that receives the
>> file name and be able to throw an error from there that aborts the
>> operation.
>
> You could define a file-handler for these files.
Yes, that looks like a solution.
For the record, the relevant info is in the Elisp manual:
Making Certain File Names “Magic”
Thanks.
^ permalink raw reply [flat|nested] 7+ messages in thread
* Re: How to reject visiting a file
2014-12-12 15:19 ` Óscar Fuentes
@ 2014-12-12 15:31 ` Stefan Monnier
2014-12-12 15:47 ` Óscar Fuentes
0 siblings, 1 reply; 7+ messages in thread
From: Stefan Monnier @ 2014-12-12 15:31 UTC (permalink / raw
To: help-gnu-emacs
>>> Is there a way to error-out when Emacs tries to visit certain file
>>> before the file is loaded? I'll like to use a hook that receives the
>>> file name and be able to throw an error from there that aborts the
>>> operation.
>> You could define a file-handler for these files.
> Yes, that looks like a solution.
> For the record, the relevant info is in the Elisp manual:
> Making Certain File Names “Magic”
I think that's going to be pretty heavyweight.
A simpler approach is something like
(defun sm-prevent-visiting-files (filename &rest _)
(if (string-match "nasty-file-name" filename)
(error "Bad! Bad file name! Bad!")))
(advice-add 'find-file-noselect :before #'sm-prevent-visiting-files)
-- Stefan
^ permalink raw reply [flat|nested] 7+ messages in thread
* Re: How to reject visiting a file
2014-12-12 15:31 ` Stefan Monnier
@ 2014-12-12 15:47 ` Óscar Fuentes
2014-12-12 15:56 ` Stefan Monnier
0 siblings, 1 reply; 7+ messages in thread
From: Óscar Fuentes @ 2014-12-12 15:47 UTC (permalink / raw
To: help-gnu-emacs
Stefan Monnier <monnier@iro.umontreal.ca> writes:
>>>> Is there a way to error-out when Emacs tries to visit certain file
>>>> before the file is loaded? I'll like to use a hook that receives the
>>>> file name and be able to throw an error from there that aborts the
>>>> operation.
>>> You could define a file-handler for these files.
>> Yes, that looks like a solution.
>> For the record, the relevant info is in the Elisp manual:
>> Making Certain File Names “Magic”
>
> I think that's going to be pretty heavyweight.
I hope not. The function will inspect the file name (possibly the
primitive too) and either throw an error or delegate to
file-name-non-special.
> A simpler approach is something like
>
> (defun sm-prevent-visiting-files (filename &rest _)
> (if (string-match "nasty-file-name" filename)
> (error "Bad! Bad file name! Bad!")))
> (advice-add 'find-file-noselect :before #'sm-prevent-visiting-files)
That was my first idea, but it was discarded because I'm not sure about
its coverage. I don't know the method a given package can use to
visit/load/read a file.
^ permalink raw reply [flat|nested] 7+ messages in thread
* Re: How to reject visiting a file
2014-12-12 15:47 ` Óscar Fuentes
@ 2014-12-12 15:56 ` Stefan Monnier
2014-12-12 16:35 ` Óscar Fuentes
0 siblings, 1 reply; 7+ messages in thread
From: Stefan Monnier @ 2014-12-12 15:56 UTC (permalink / raw
To: help-gnu-emacs
>> (defun sm-prevent-visiting-files (filename &rest _)
>> (if (string-match "nasty-file-name" filename)
>> (error "Bad! Bad file name! Bad!")))
>> (advice-add 'find-file-noselect :before #'sm-prevent-visiting-files)
> That was my first idea, but it was discarded because I'm not sure about
> its coverage. I don't know the method a given package can use to
> visit/load/read a file.
find-file-noselect is the "single entry" used normally to visit a file
in a normal file buffer, no matter how this is triggered (find-file,
find-file-other-window, clinking on an error in a *compile* buffer, ...)
so it should have excellent coverage.
This advice doesn't prevent Emacs from accessing the file (e.g. you can
still use insert-file-contents to read the file and put it in some
buffer and you can still use M-x insert-file as well), but it would be
*very* weird for a package to use such an approach over just calling
find-file-noselect.
I'll let you judge if it's good enough for your use case.
Stefan
^ permalink raw reply [flat|nested] 7+ messages in thread
* Re: How to reject visiting a file
2014-12-12 15:56 ` Stefan Monnier
@ 2014-12-12 16:35 ` Óscar Fuentes
0 siblings, 0 replies; 7+ messages in thread
From: Óscar Fuentes @ 2014-12-12 16:35 UTC (permalink / raw
To: help-gnu-emacs
Stefan Monnier <monnier@iro.umontreal.ca> writes:
>>> (defun sm-prevent-visiting-files (filename &rest _)
>>> (if (string-match "nasty-file-name" filename)
>>> (error "Bad! Bad file name! Bad!")))
>>> (advice-add 'find-file-noselect :before #'sm-prevent-visiting-files)
>> That was my first idea, but it was discarded because I'm not sure about
>> its coverage. I don't know the method a given package can use to
>> visit/load/read a file.
>
> find-file-noselect is the "single entry" used normally to visit a file
> in a normal file buffer, no matter how this is triggered (find-file,
> find-file-other-window, clinking on an error in a *compile* buffer, ...)
> so it should have excellent coverage.
>
> This advice doesn't prevent Emacs from accessing the file (e.g. you can
> still use insert-file-contents to read the file and put it in some
> buffer and you can still use M-x insert-file as well), but it would be
> *very* weird for a package to use such an approach over just calling
> find-file-noselect.
>
> I'll let you judge if it's good enough for your use case.
I wish to stop Emacs from loading pdf files unless a given feature is
present. IMO pdf-tools [1] is an usable Emacs PDF viewer but, when it is
absent, Emacs defaults to doc-view (with terrible consecuences) or to
visiting the pdf file as if it were a regular one (and you end with a
garbage-filled buffer.)
Advising find-file-noselect would prevent the later, but I was not so
sure about the former case. A quick experiment shows that it works. Now
only remains my dislike for advising as the only reason for using Eli's
suggestion.
1. https://github.com/politza/pdf-tools
^ permalink raw reply [flat|nested] 7+ messages in thread
end of thread, other threads:[~2014-12-12 16:35 UTC | newest]
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-- links below jump to the message on this page --
2014-12-12 1:46 How to reject visiting a file Óscar Fuentes
2014-12-12 8:01 ` Eli Zaretskii
2014-12-12 15:19 ` Óscar Fuentes
2014-12-12 15:31 ` Stefan Monnier
2014-12-12 15:47 ` Óscar Fuentes
2014-12-12 15:56 ` Stefan Monnier
2014-12-12 16:35 ` Óscar Fuentes
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