tree schema FEATURE emit paths suitable for key search
Motivation: consider the structure with list hierarchy:
container earth {
list country {
key name;
leaf name {....};
list city {
key name;
......
and you want to find cities in some country. Path built with LYSC_PATH_DATA_PATTERN (/earth/country[name='%s']/city[name='%s']/name) can't be used for this task because it contains predicate for city (so you must know it in advance), and path built with LYSC_PATH_DATA (/earth/country/city/name) will find cities in the entrie earth, not limited by country.
New LYSC_PATH_KEY_PATTERN will emit /earth/country[name='%s']/city/name here making the task doable.
I am sorry but I do not see much value in such an addition. There are lots of other path patterns with possible use-cases and none of them supported. So I suppose if you really need such a path, you have to generate it yourself.