Re: TRAMP VC optimization: also breaks process filters -_-

[Michael Albinus <michael.albinus@gmx.de>]

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Stefan Monnier <monnier@iro.umontreal.ca> writes:

Hi,

>> I'm sad to report that blocking timers in TRAMP is not sufficient to avoid
>> it breaking other operations: process filters can also run while TRAMP is
>> sending, and waiting for the result of, a command.
>
> I'm not sure what is the problem with timers and/or process filters
> (e.g. I don't see any process filters in your backtrace), so maybe I'm
> misunderstanding the problem, but FWIW, here's what I noticed:
>
>>   tramp-user-error(nil "Not a Tramp file name: \"%s\"" "/Users/slippycheeze/.emacs.d/network-security.data")
>>   tramp-dissect-file-name("/Users/slippycheeze/.emacs.d/network-security.data")
>>   tramp-vc-file-name-handler(expand-file-name "/Users/slippycheeze/.emacs.d/network-security.data" "/gssh:slippycheeze.X.XXXXXXXX.XXX:")
>
> This indicates that Tramp gets confused and thinks that the
> tramp-vc-file-name-handler was called in response to expand-file-name on
> the file "/Users/slippycheeze/.emacs.d/network-security.data" whereas
> it's called because of the directory argument.
>
> So I believe the (untested) patch below should fix the immediate problem.
> Can you confirm?
>
> Michael?

Yes, the analysis is correct. However, we don't need to check this for
every Tramp invocation. Daniel's reports have been covered always
vc-registered. And indeed, the related `tramp-vc-file-name-handler'
seems to expect always a Tramp file name, which is not true for filters
and sentinels which run for non-Tramp processes.

Daniel, does the appended patch fixes the issue for you?

>         Stefan

Best regards, Michael.


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*** /tmp/ediffKys9Ze	2019-05-07 17:22:48.298108293 +0200
--- /home/albinus/src/tramp/lisp/tramp-sh.el	2019-05-07 17:19:08.563550390 +0200
***************
*** 3550,3573 ****
  	   (tramp-replace-environment-variables
  	    (apply #'tramp-file-name-for-operation operation args)))
  	  (fn (assoc operation tramp-sh-file-name-handler-alist)))
!       (with-parsed-tramp-file-name filename nil
! 	(cond
! 	 ;; That's what we want: file names, for which checks are
! 	 ;; applied.  We assume that VC uses only `file-exists-p' and
! 	 ;; `file-readable-p' checks; otherwise we must extend the
! 	 ;; list.  We do not perform any action, but return nil, in
! 	 ;; order to keep `vc-registered' running.
! 	 ((and fn (memq operation '(file-exists-p file-readable-p)))
! 	  (add-to-list 'tramp-vc-registered-file-names localname 'append)
! 	  nil)
! 	 ;; `process-file' and `start-file-process' shall be ignored.
! 	 ((and fn (eq operation 'process-file) 0))
! 	 ((and fn (eq operation 'start-file-process) nil))
! 	 ;; Tramp file name handlers like `expand-file-name'.  They
! 	 ;; must still work.
! 	 (fn (save-match-data (apply (cdr fn) args)))
! 	 ;; Default file name handlers, we don't care.
! 	 (t (tramp-run-real-handler operation args)))))))

  (defun tramp-sh-handle-file-notify-add-watch (file-name flags _callback)
    "Like `file-notify-add-watch' for Tramp files."
--- 3550,3579 ----
  	   (tramp-replace-environment-variables
  	    (apply #'tramp-file-name-for-operation operation args)))
  	  (fn (assoc operation tramp-sh-file-name-handler-alist)))
!       ;; If connection is not established yet, or if it is not a Tramp
!       ;; file, run the real handler.  This can happen if timers,
!       ;; process filters, or process sentinels not related to us are
!       ;; activated.
!       (if (not (tramp-connectable-p filename))
! 	  (tramp-run-real-handler operation args)
! 	(with-parsed-tramp-file-name filename nil
! 	  (cond
! 	   ;; That's what we want: file names, for which checks are
! 	   ;; applied.  We assume that VC uses only `file-exists-p' and
! 	   ;; `file-readable-p' checks; otherwise we must extend the
! 	   ;; list.  We do not perform any action, but return nil, in
! 	   ;; order to keep `vc-registered' running.
! 	   ((and fn (memq operation '(file-exists-p file-readable-p)))
! 	    (add-to-list 'tramp-vc-registered-file-names localname 'append)
! 	    nil)
! 	   ;; `process-file' and `start-file-process' shall be ignored.
! 	   ((and fn (eq operation 'process-file) 0))
! 	   ((and fn (eq operation 'start-file-process) nil))
! 	   ;; Tramp file name handlers like `expand-file-name'.  They
! 	   ;; must still work.
! 	   (fn (save-match-data (apply (cdr fn) args)))
! 	   ;; Default file name handlers, we don't care.
! 	   (t (tramp-run-real-handler operation args))))))))

  (defun tramp-sh-handle-file-notify-add-watch (file-name flags _callback)
    "Like `file-notify-add-watch' for Tramp files."