[debbugs-tracker] bug#18535: closed (tramp alters `vc-handled-backends')

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Your message dated Thu, 25 Sep 2014 09:07:40 -0400
with message-id <address@hidden>
and subject line Re: bug#18535: tramp alters `vc-handled-backends'
has caused the debbugs.gnu.org bug report #18535,
regarding tramp alters `vc-handled-backends'
to be marked as done.

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-- 
18535: http://debbugs.gnu.org/cgi/bugreport.cgi?bug=18535
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> --- Begin Message ---
>
>
>
> Subject: 
>
> tramp alters `vc-handled-backends'
>
>
>
>
> Date: 
>
> Tue, 23 Sep 2014 12:53:38 +0200
>
>
>
>
> `tramp-sh-handle-vc-registered' can permanently alter the value of
> `vc-handled-backends' causing Emacs to stop recognizing version
> controlled files as such.  This happened to me a couple of times after
> having pressed `C-g' while some `tramp' operation was apparently
> hanging.
>
> Here is a patch:
>
> === modified file 'lisp/ChangeLog'
> --- lisp/ChangeLog    2014-09-16 13:36:04 +0000
> +++ lisp/ChangeLog    2014-09-23 09:27:10 +0000
> @@ -1,4 +1,9 @@
> +2014-09-23  Emilio C. Lopes  <address@hidden>
> +
> +    * net/tramp-sh.el (tramp-sh-handle-vc-registered): use `unwind-protect'
> +    to avoid altering `vc-handled-backends' permanently.
> +
>  2014-09-22  Kan-Ru Chen  <address@hidden>
>
>     * window.el (fit-window-to-buffer): When counting buffer width,
>     count the whole visible buffer.  Correctly convert the body-height
> === modified file 'lisp/net/tramp-sh.el'
> --- lisp/net/tramp-sh.el    2014-09-08 15:52:04 +0000
> +++ lisp/net/tramp-sh.el    2014-09-23 09:27:10 +0000
> @@ -3456,30 +3456,33 @@
>      ;; calls shall be answered from the file cache.  We unset
>      ;; `process-file-side-effects' and `remote-file-name-inhibit-cache'
>      ;; in order to keep the cache.
> -    (let ((vc-handled-backends vc-handled-backends)
> +    (let ((vc-handled-backends-saved vc-handled-backends)
>            remote-file-name-inhibit-cache process-file-side-effects)
>        ;; Reduce `vc-handled-backends' in order to minimize process calls.
> -      (when (and (memq 'Bzr vc-handled-backends)
> -             (boundp 'vc-bzr-program)
> -             (not (with-tramp-connection-property v vc-bzr-program
> -                (tramp-find-executable
> -                 v vc-bzr-program (tramp-get-remote-path v)))))
> -        (setq vc-handled-backends (delq 'Bzr vc-handled-backends)))
> -      (when (and (memq 'Git vc-handled-backends)
> -             (boundp 'vc-git-program)
> -             (not (with-tramp-connection-property v vc-git-program
> -                (tramp-find-executable
> -                 v vc-git-program (tramp-get-remote-path v)))))
> -        (setq vc-handled-backends (delq 'Git vc-handled-backends)))
> -      (when (and (memq 'Hg vc-handled-backends)
> -             (boundp 'vc-hg-program)
> -             (not (with-tramp-connection-property v vc-hg-program
> -                (tramp-find-executable
> -                 v vc-hg-program (tramp-get-remote-path v)))))
> -        (setq vc-handled-backends (delq 'Hg vc-handled-backends)))
> -      ;; Run.
> -      (ignore-errors
> -        (tramp-run-real-handler 'vc-registered (list file))))))))
> +          (unwind-protect
> +              (progn
> +                (when (and (memq 'Bzr vc-handled-backends)
> +                           (boundp 'vc-bzr-program)
> +                           (not (with-tramp-connection-property v
> vc-bzr-program
> +                                  (tramp-find-executable
> +                                   v vc-bzr-program
> (tramp-get-remote-path v)))))
> +                  (setq vc-handled-backends (delq 'Bzr vc-handled-backends)))
> +                (when (and (memq 'Git vc-handled-backends)
> +                           (boundp 'vc-git-program)
> +                           (not (with-tramp-connection-property v
> vc-git-program
> +                                  (tramp-find-executable
> +                                   v vc-git-program
> (tramp-get-remote-path v)))))
> +                  (setq vc-handled-backends (delq 'Git vc-handled-backends)))
> +                (when (and (memq 'Hg vc-handled-backends)
> +                           (boundp 'vc-hg-program)
> +                           (not (with-tramp-connection-property v vc-hg-program
> +                                  (tramp-find-executable
> +                                   v vc-hg-program
> (tramp-get-remote-path v)))))
> +                  (setq vc-handled-backends (delq 'Hg vc-handled-backends)))
> +                ;; Run.
> +                (ignore-errors
> +                  (tramp-run-real-handler 'vc-registered (list file))))
> +            (setq vc-handled-backends vc-handled-backends-saved)))))))
>
>  ;;;###tramp-autoload
>  (defun tramp-sh-file-name-handler (operation &rest args)
>
>
>
> --- End Message ---
> --- Begin Message ---
>
>
>
> Subject: 
>
> Re: bug#18535: tramp alters `vc-handled-backends'
>
>
>
>
> Date: 
>
> Thu, 25 Sep 2014 09:07:40 -0400
>
>
>
>
> User-agent: 
>
> Gnus/5.13 (Gnus v5.13) Emacs/24.4.50 (gnu/linux)
>
>
>
>
> >> The current code uses a `let' binding, which uses the same mechanism as
> >> unwind-protect, so I don't think that's the source of a the problem.
> > Is this common behavior in Lisps?  I could not find any reference to
> > this in the Elisp manual.
>
> The Elisp manual's description is not in terms of implementation, so it
> doesn't say that, but it does document that behavior.  E.g.:
>
>    When that local binding is no longer in effect, the
>    previously shadowed value (or lack of one) comes back.
>
> >> The `delq' look dangerous on the other hand.  Shouldn't these be
> >> `remq' instead?
> > yes, this seems to solve the problem.
>
> Thanks, installed,
>
>
>         Stefan
>
>
> --- End Message ---