How do I port this very generic Query function to bevy 0.17 ?

[Strackeror]

So, we have this function in the project, which I'm trying to bring from 0.13 to 0.17

fn query_mut<T: QueryData>(
    world: &'_ mut World,
    check: impl Fn(&QueryItem<T>) -> bool,
) -> Result<QueryItem<'_, T>, String> {
    let mut query = world.query::<T>();
    query
        .iter_mut(world)
        .find(check)
        .ok_or_else(|| format!("Could not find obj {}", type_name::<T>()))
}

It's not meant to be very efficient, it's mostly used for unit tests and some specific scripting purposes. I'm having a lot of trouble making this function work with the new system where QueryItem has both 'w and 's lifetimes.
From what I'm understanding, the issue is situations where the QueryItem has a reference to the underlying query state, but this function is only used for (&ComponentA, &ComponentB, Entity) type queries where only direct references to the world would be returned.
Is this possible to express with generics ? If so how ?

[hymm]

I think this is a hard problem to fix, since the new 's lifetime is tied to the local query state variable. So you'll keep getting lifetime errors about lifetime does not live long enough. If it's just for internal use you could transmute the second lifetime to 'static, since in your case it isn't tied to any actual data.

Bevy could potentially add a unsafe trait that would be implemented for QueryData that doesn't return data from the state. Not sure if it would be worth the complexity or not given this niche use case.

[hymm]

found out that there is ReleaseStateQueryData that allows you to return 'static for the second lifetime if the QueryData allows it. https://docs.rs/bevy/latest/bevy/ecs/query/trait.ReleaseStateQueryData.html

[Strackeror]

Well i'll be damned, it was right under my nose the whole time. It's just under the QueryItem definitions which I checked over multiple times too hahaha.

Here is the function fixed with the new trait:

pub fn find_<'w, T: ReleaseStateQueryData>(
        world: &'w mut World,
        check: impl Fn(&QueryItem<T>) -> bool,
    ) -> Result<QueryItem<'w, 'static, T>, String> {
        world
            .query::<T>()
            .iter_mut(world)
            .find(check)
            .map(|item| T::release_state(item))
            .ok_or_else(|| format!("Could not find query {}", type_name::<T>()))
    }

Annoyingly, I had already modified all the calls to the function to pass a &mut QueryState as an additional parameter, but I'll definitely take that new method, thanks !