Trait cucumber::codegen::ToWorldFuture

source ·

pub trait ToWorldFuture {
    type Future: Future;

    // Required method
    fn to_world_future(&self) -> Self::Future;
}

Available on crate feature macros only.

Expand description

Return-type polymorphism over asyncness for a #[world(init)] attribute of a #[derive(World)] macro.

It allows to accept both sync and async functions as an attribute’s argument, by automatically wrapping sync functions in a future::Ready.

impl cucumber::World for World {
    type Error = anyhow::Error;

    async fn new() -> Result<Self, Self::Error> {
        use cucumber::codegen::{
            IntoWorldResult as _, ToWorldFuture as _,
        };

        fn as_fn_ptr<T>(v: fn() -> T) -> fn() -> T {
            v
        }

        //           `#[world(init)]`'s value
        //          ⌄⌄⌄⌄⌄⌄⌄⌄⌄⌄⌄⌄⌄⌄⌄⌄⌄⌄⌄⌄⌄⌄⌄⌄⌄⌄
        (&as_fn_ptr(<Self as Default>::default))
            .to_world_future() // maybe wraps into `future::Ready`
            .await
            .into_world_result()
            .map_err(Into::into)
    }
}