Avoid TRAMP related errors from blocking ivy-...-buffer commands

[pcrama]

Otherwise, on my system (Ubuntu LTS 18.04, Emacs 27.0.50), using e.g. ivy-switch-buffer fails if a ZIP file listing has been inserted into a dired buffer (I believe that kill-buffer is also affected once ivy-mode is enabled).

How to reproduce the problem (i.e. without this patch):

1. Create a /tmp/minimal-init.el file (this assumes that you package-install ivy in your normal Emacs setup first):

   (require 'package)
   (setq package-directory-list (list (locate-user-emacs-file "elpa/")))
   (package-initialize)
   (require 'ivy)

2. Start Emacs with minimal customization:

   emacs --quick --load /tmp/minimal-init.el

3. M-x dired and navigate to a directory containing a ZIP file. Select the ZIP file & dired-maybe-insert-subdir (i.e. shortcut key i) it into the dired buffer. It should look like this:

   /tmp/issue:
   total used in directory 32 available 3818908
   drwxr-x---  2 user user  4096 Nov  6 11:14 .
   drwxrwxrwt 21 root root 24576 Nov  6 11:14 ..
   -rw-r-----  1 user user   152 Nov  6 11:14 b.zip
   
   /tmp/issue/b.zip/:
   total used in directory 0 available 3818908
   dr-x------  0 user user 0 1970-01-01  .
   dr-x------  0 user user 0 1970-01-01  ..
   -r--------  0 user user 0 11-06 11:14 a
   

4. Navigate to the file (i.e. go to the line with a and dired-find-file, i.e. press Enter).

5. M-x ivy-switch-buffer and nothing happens except an error message

   tramp-file-name-handler: Process *tramp/archive file%3A%2F%2F%2Ftmp%2Fissue%2Fb.zip* not running
   

[abo-abo]

Thanks.

[Alexander-Shukaev]

You should almost never use ignore-errors because it

1. swallows other potentially important errors;
2. pretty bad at documenting the intent and actual reason for it being there.

In case of TRAMP-related errors, it's better to explicitly disable TRAMP handlers by let-binding tramp-mode to nil. In fact, here is a gem from my configuration of ivy since the beginning:

  (defun init-ivy-switch-buffer
      (function &rest ...)
    (let (tramp-mode)
      (apply function ...)))
  (advice-add #'ivy-switch-buffer
              :around
              #'init-ivy-switch-buffer)

[abo-abo]

1. swallows other potentially important errors;

In this case it doesn't though. It simply returns nil if file-remote-p could not return a truthy value. That's exactly what we want from file-remote-p.