Filter groups break when reverting buffer with expanded subtrees

[nnicandro]

I've been running into the problem where filter groups do not get displayed after reverting the buffer and point is on a line that is contained within the region of a subtree.

It seems the culprit is that (ignore-errors (dired-next-subdir 0)) in dired-filter-group--apply evaluates to nil in the above scenario. I'm assuming because dired-next-subdir is not aware of subtree's.

I made a fix for this that just folds the subtrees, applies the filter groups, and then re-expands the subtrees again:

(defun dired-filter-group-subtree-hack (orig-fun filter-group)
  "Fold subtree's, apply filter groups, expand subtrees.

If `dired-subtree' is enabled, fold all of the expanded subtrees
before calling `dired-filter-group--apply' and re-expand them
after.

This avoids breaking the filter groups machinery when subtrees are
expanded and the buffer is reverted."
  (let* ((subtrees (and (featurep 'dired-subtree)
				     (let ((dired-filter-keep-expanded-subtrees t))
					(eval (dired-filter--mark-unmarked 't))
					(reverse dired-filter--expanded-dirs))))
		 (prefix (car subtrees)))
	;; fold all expanded subtrees
	(when subtrees
	  (dired-utils-goto-line prefix)
	  (dired-subtree-toggle)
	  (--each-while (cdr subtrees)
		  (unless (string-prefix-p prefix it) (setq prefix it))
		(save-excursion
		  (dired-utils-goto-line it)
		  (dired-subtree-toggle))))
	(funcall orig-fun filter-group)
	;; re-expand folded subtrees
	(when subtrees
	  (--each subtrees
		(save-excursion
		  (dired-utils-goto-line it)
		  (dired-subtree-insert))))))

(advice-add 'dired-filter-group--apply :around #'dired-filter-group-subtree-hack)

Another possible solution would be to remove and then re-apply the subtree overlays instead of having to re-insert the contents of all the subtrees.

It would be great to see if someone more familiar with the internals could see if there is a better option.

[Fuco1]

Hmm, thanks for the report AND the code ;) I will check it out.

I think the complete solution would be to either advice or redefine dired-next-subdir to make it aware of the context, it is probably the problem as you discussed above.