Allow for virtual-buffer configuration.

[gusbrs]

This is a feature request, alongside a proposed implementation.

ivy-use-virtual-buffers is brilliant, and is suggested in the documentation as one of the most basic variables to enable in Ivy. However, it bundles together recent files and bookmarks, which are quite different things. Furthermore, it doesn't treat bookmarks as such, but by design (#567, #347) it only offers the files to which the bookmarks refer.

Given that, it would be nice if Ivy allowed us to choose what to include in the virtual-buffers. If you like the idea, it could go about like:

(defcustom ivy-use-virtual-buffers nil
  "When non-nil, add recent files and/or bookmarks to `ivy-switch-buffer'.
The value `recentf' includes only recent files to the virtual
buffers list, whereas the value `bookmarks' does the same for
bookmarks.  Any other non-nil value includes both."
  :type '(choice
          (const :tag "Don't use virtual buffers" nil)
          (const :tag "Recent files" recentf)
          (const :tag "Bookmarks" bookmarks)
          (const :tag "All virtual buffers" t)))

(defun ivy--virtual-buffers ()
  "Adapted from `ido-add-virtual-buffers-to-list'."
  (require 'bookmark)
  (unless recentf-mode
    (recentf-mode 1))
  ;; start of changes
  (bookmark-maybe-load-default-file)
  (let* ((vb-recent recentf-list)
         (vb-bkm (delete "   - no file -"
                         (delq nil (mapcar #'bookmark-get-filename
                                           bookmark-alist))))
         (vb-list (cond ((eq ivy-use-virtual-buffers 'recentf)
                         vb-recent)
                        ((eq ivy-use-virtual-buffers 'bookmarks)
                         vb-bkm)
                        (ivy-use-virtual-buffers
                         (append vb-recent vb-bkm))
                        (t nil)))
         virtual-buffers)
    (dolist (head vb-list)
      ;; end of changes
      (let* ((file-name (if (stringp head)
                            head
                          (cdr head)))
             (name (cond ((eq ivy-virtual-abbreviate 'name)
                          (file-name-nondirectory file-name))
                         ((eq ivy-virtual-abbreviate 'abbreviate)
                          (abbreviate-file-name file-name))
                         (t
                          (expand-file-name file-name)))))
        (when (equal name "")
          (setq name
                (if (consp head)
                    (car head)
                  (file-name-nondirectory (directory-file-name file-name)))))
        (unless (or (equal name "")
                    (get-file-buffer file-name)
                    (assoc name virtual-buffers))
          (push (cons (copy-sequence name) file-name) virtual-buffers))))
    (when virtual-buffers
      (dolist (comp virtual-buffers)
        (put-text-property 0 (length (car comp))
                           'face 'ivy-virtual
                           (car comp)))
      (setq ivy--virtual-buffers (nreverse virtual-buffers))
      (mapcar #'car ivy--virtual-buffers))))

If you'd like more comments on why I think this is useful (particularly, the possibility of being able to exclude bookmarks, but keeping recent files, of course), I can expand.

[abo-abo]

This is a good idea, and the change look good to me. Please PR.

[gusbrs]

Nice, I'll do so. But, first, I am a PR noob. I should be able to do it, but don't hesitate to correct me if need be, and please be patient. And, second, I currently don't (yet) have the papers signed with the FSF. I presume this amounts to a tiny change, so it would still be ok. Is that correct?

[abo-abo]

Yes, changes up to 15 lines are counted as tiny and don't need an assignment.

[gusbrs]

Perfect, I'll prepare it then. Thanks!