unique constraints for Yang leaf-list across all nodes in a list - yang

Question

I have below yang models
container PORT {
description "PORT part of config_db.json";
list PORT_LIST {
key "name";
leaf name {
type string {
length 1..128;
}
}
leaf-list lanes {
type string {
length 1..128;
}
}
}
}
And below config
PORT": {
"PORT_LIST": [
{
"name": "Ethernet8",
"lanes": ["65", "66"]
},
{
"name": "Ethernet9",
"lanes": ["65", "67"]
}
]
}
How to add a constraint, 'must' or 'unique' such that elements of leaf-list 'lanes' are unique across all nodes in PORT_LIST. In above example value '65' in 'lanes' field should be allowed only in one node.

Answer 1

The unique statement may only refer to one or more leaf statements, so that is not an option.
You should be able to achieve a similar result with a must statement and a condition like this:
module c {
yang-version 1.1;
namespace "c:uri";
prefix "c";
container PORT {
description "PORT part of config_db.json";
list PORT_LIST {
key "name";
must "count(lanes[current()/preceding-sibling::PORT_LIST/lanes = .]) = 0" {
error-message "Lanes entries must be unique accross all entries of PORT_LIST";
}
leaf name {
type string {
length 1..128;
}
}
leaf-list lanes {
type string {
length 1..128;
}
}
}
}
}
The condition says something along the lines of: if there are any lanes for this PORT_LIST entry, none of them should have the same value as the lanes in any of the PORT_LIST entries that come before this one.
<?xml version="1.0" encoding="utf-8"?>
<config xmlns="urn:ietf:params:xml:ns:netconf:base:1.0">
<PORT xmlns="c:uri">
<PORT_LIST>
<name>Ethernet8</name>
<lanes>65</lanes>
<lanes>66</lanes>
</PORT_LIST>
<PORT_LIST>
<name>Ethernet9</name>
<lanes>65</lanes>
<lanes>67</lanes>
</PORT_LIST>
</PORT>
</config>
Error at (9:5): failed assert at "/nc:config/c:PORT/c:PORT_LIST": Lanes entries must be unique accross all entries of PORT_LIST
This is just a quick example, there may be more efficient ways to define the condition.