[BUG] org-element-cache: The inherited property is set wrong

[Anders Johansson]

Hi,
I had some trouble with completing tags, where the already set tags
were wrongly identified. I have dug this down to a problem with
caching.

with org-element-use-cache=t and org-use-tag-inheritance=t
--- Org
* headline 1 :tag1:
** headline 2 :tag2:
--- end org

When invoking org-set-tags-command (and quitting),  on headline 1,
then headline 2, then headline 1 again, "tag1" is no longer shown as
one of the existing tags in the minibuffer. This is because it has
erronously been assigned an :inherited property in the
cache-representation for headline 1 when inherited tags were
calculated for headline 2. This happens in org-get-tags, where
inherited tags are parsed from the cache and given the :inherited
property, but unfortunately this is done to the same string objects,
so that this property is added in the cache tree both for the taglist
of headline 1 and headline 2.

(cl-copy-list cached-tags) is used there, but only copies the list and
not the string objects.

A solution that seems to work for me was to change
 (cl-copy-list cached-tags)
to
(mapcar #'copy-sequence cached-tags)

(found it here: https://stackoverflow.com/a/47794586)

I don’t know if this is the best solution though.
Perhaps this is needed also in org--get-local-tags where a similar
thing is done? (but only the fontification seems to matter there)


Best,
Anders Johansson (who is otherwise as mentioned in an earlier
discussion very appreciative of org-element-cache)