index_zones vs html_index_attrs

It looks like index_zones disables html_index_attrs and it may be wrong:

index_zones + html_index_attrs:

mysql> create table t(f text) html_strip='1' html_index_attrs='a=href' index_zones='a';  
 
insert into t values(0, '<a href="href1" title="title1">a1</a> between <a href="href2">a2</a>'),(0,'<a href="href3">between</a>'); 
 
mysql> select * from t where match('href1'); 
Empty set (0.00 sec) 
 
mysql> select * from t where match('ZONE:a a1'); 
+---------------------+----------------------------------------------------------------------+ 
| id                  | f                                                                    | 
+---------------------+----------------------------------------------------------------------+ 
| 1514175226210943028 | <a href="href1" title="title1">a1</a> between <a href="href2">a2</a> | 
+---------------------+----------------------------------------------------------------------+ 
1 row in set (0.01 sec) 
 
mysql> select * from t where match('ZONE:a href2'); 
Empty set (0.00 sec) 
 
mysql> select * from t where match('ZONE:a href1'); 
Empty set (0.00 sec) 

I.e. there seems to be no way to find href1, href2.

Without index_zones:

mysql> create table t(f text) html_strip='1' html_index_attrs='a=href';  
 
insert into t values(0, '<a href="href1" title="title1">a1</a> between <a href="href2">a2</a>'),(0,'<a href="href3">between</a>'); 
 
mysql> select * from t where match('href1'); 
+---------------------+----------------------------------------------------------------------+ 
| id                  | f                                                                    | 
+---------------------+----------------------------------------------------------------------+ 
| 1514175226210943030 | <a href="href1" title="title1">a1</a> between <a href="href2">a2</a> | 
+---------------------+----------------------------------------------------------------------+ 
1 row in set (0.00 sec) 

At first glance it's not clear if it's a bug or not. The task is to figure it out.

Once done please update https://forum.manticoresearch.com/t/how-to-filter-on-data-indexed-using-html-index-attrs-setting/734/8

Reproduce the SQL examples comparing index_zones with html_index_attrs and without index_zones. Determine whether attribute values such as href1 and href2 are intended to remain searchable inside the zone, then document the conclusion and update the linked Manticore forum discussion.