Improving the ergonomics of relations

[krispya]

There is a barebones implementation of relations in Koota, but as people use it there is a need to improve the DX and ergonomics of using them. I'd like to hear feedback from users on what usage patterns they have that could be simplified or uses they wish they had that is not possible with relations right now.

Here is a longstanding one: #4

Another is being able to set state on relation stores in an add call.

// This is currently not possible
entity.add(Contains(gold, { amount: 10 })
// Instead it must be done in two calls
entity.add(Contains(gold))
entity.set(Contains(gold), { amount: 10 })

What else do you need?

[n4t4l]

Hi krispya! Other than seconding the want for a way to pass traits into relationships to use as a filter for queries, there are two functionalities that i think would really improve ergonomics.
The first is being able to get the target entity from the relation component, afaik the only way to get both the target and the data from a relation component is by

for (const e of world.query(Relation('*'))) {
   const [target,relation] = e.targetsFor(Relation).map(target => [target,e.get(Contains(target))])
}

So we could not, for example, get this inside a updateEach, therefore not being able to change the value without triggering change detection. (is there a way to silence change detection outside of a updateEach? that would be nice to have too :) )

Another one is in relation to the wildcards. Both Wildcard and '*' at the moment can only be used to query, it would be nice if Relation('*') worked as [TargetsFor(Relation),Relation(target)] in the sense that it would then return a collection of all relations of that type by entity.
By extension, Wildcard would also be more versatile if it returned all relations each entity in the query result had with that entity, but then we'd need some way to identify what relations those are, and that ends up bumping into the named traits stuff you guys are already looking into.

Overall, i think relations are already extremely useful, especially when adapted to be used as a "multiple instance component without creating a bunch of archetypes" kind of thing, and are only a few steps away from being one of the best things about Koota.
Oh, and you say in your post setting the value of the relation on add is needed, i wasnt clear enough in my response but chest.add(Contains(silver)({amount:50})); works! I'll edit my answer to clarify.