Hi! I think maybe there's a bug in org-save-outline-visibility, or else I misunderstand what that macro is supposed to do. Test case:
1. Start Emacs 26.0.91 with -Q and load org-mode from master (release_9.1.6-419-g4b2006).
2. Make an org-mode buffer with contents:
3. Fold the PROPERTIES drawer by moving to the line with :PROPERTIES: and hitting TAB.
4. M-: (org-save-outline-visibility t (org-show-all)) RET
Expected result: PROPERTIES drawer is still folded
Observed result: PROPERTIES drawer is no longer folded, its contents have become visible
Should org-save-outline-visibility save the visibility of drawers along with other visibility?
I am wondering if this is perhaps a consequence of 4403d4685e19, "Give drawers their own invisibility spec", where the 'org-hide-drawer invisibility spec was introduced? As a consequence, org-outline-overlay-data (called by org-save-outline-visibility) no longer saves the invisible overlays for drawers, since those overlays' 'invisible property is no longer 'outline, but instead 'org-hide-drawer.