[O] Bug: Matching tags: results incomplete when mixing group tags and their ancestors [9.1.7 (9.1.7-12-g74f6ed-elpaplus @ /home/martin/.emacs.d/elpa/org-plus-contrib-20180305/)]

[Martin Kampas]

Hi,

Here is an example Org file:

------------
#+TAGS: [ tag1 : tag2 ] [ tag2 : tag3 ] [ tag3 : tag4 ]
* Tag1           :tag1:
* Tag2           :tag2:
* Tag3           :tag3:
* Tag4           :tag4:
------------

Searching headlines by tags works well unless you combine a group tag together 
with some of its ancestor tags in the query.

1) GOOD - Searching for "tag1" marks all four headlines.
2) GOOD - Searching for "tag3" marks headlines "Tag3" and "Tag4".
3) BAD - Searching for "tag1+tag3" marks just headline "Tag3" providing an 
incomplete result. Expected result: headlines "Tag3" and "Tag4" are marked.

With more complex tag set it may happen quite easily that such a search is done.

The bug seems to be in org-tags-expand.

(org-tags-expand "tag1")
#("{\\<\\(?:tag[1-4]\\)\\>}" 0 20 (grouptag t))
(org-tags-expand "tag3")
#("{\\<\\(?:tag[34]\\)\\>}" 0 19 (grouptag t))
(org-tags-expand "tag1+tag3")
#("{\\<\\(?:tag[1-4]\\)\\>}+tag3" 0 20 (grouptag t))

In the third invocation "tag3" was left unexpanded.

Best regards,
Martin


Emacs  : GNU Emacs 25.3.1 (x86_64-pc-linux-gnu, GTK+ Version 3.22.26)
 of 2018-02-09
Package: Org mode version 9.1.7 (9.1.7-12-g74f6ed-elpaplus @ 
/home/martin/.emacs.d/elpa/org-plus-contrib-20180305/)