Why we have to pass clients array to modifyGroup command in dynamic security plugin? - mqtt

Question

In mosquitto docs, we have to pass both roles and clients whenever we are updating a group. When we pass it, the client belongs to group, but the client object is not updated and the group where it was attached is not listened on GetGroup command.
I thought there is a hierarchy of Mqtt Entities (Clients->Groups->Roles) and lower level entities cannot contain higher level entities, but groups somehow can.
Why we have to pass clients array to modifyGroup command?

Answer 1

Only the entries that are present in the modifyGroup object are modified. So if you send:
{
"commands":[{
"command": "modifyGroup",
"groupname": "mygroup",
"clients": [ { "username": "client", "priority": 1 } ]
}]
}
Then mygroup will be modified to have a single user client.
If instead you send:
{
"commands":[{
"command": "modifyGroup",
"groupname": "mygroup",
"clients": []
}]
}
Then mygroup will be modified to have no clients.
Finally, if you send:
{
"commands":[{
"command": "modifyGroup",
"groupname": "mygroup",
"textdescription": "text"
}]
}
Then the group members will not be modified.
If you don't have this behaviour, please update your question with examples of exactly what you are sending that produces an error.

Answer 2

Both roles and clients are marked as optional in the example for modifying a group
Modify Group
Command:
{
"commands":[
{
"command": "modifyGroup",
"groupname": "group to modify",
"textname": "", # Optional
"textdescription": "", # Optional
"roles": [
{ "rolename": "role", "priority": 1 }
], # Optional
"clients": [
{ "username": "client", "priority": 1 }
] # Optional
}
]
}