Implement Promise Race

[komyg]

No description provided.

[komyg]

Hey @aapoalas, in this implementation of Promise.race I am using the infrastructure that we already have for PromiseGroup.

This means that we are creating a PromiseGroupRecord with all its elements, such as result_array and remaining_elements_count, which are not used by the Promise.race implementation:

pub struct PromiseGroupRecord<'a> {
    pub(crate) promise_group_type: PromiseGroupType,
    pub(crate) remaining_elements_count: u32,
    pub(crate) result_array: Array<'a>,
    pub(crate) promise: Promise<'a>,
}

We can keep it like this, or I can create a data structure specially for Promise.race that doesn't have any unused fields. This means also creating heap vectors to hold a PromiseRaceRecord struct. What do you prefer?

[aapoalas]

LGTM :)

[aapoalas]

Hey @aapoalas, in this implementation of Promise.race I am using the infrastructure that we already have for PromiseGroup.

This means that we are creating a PromiseGroupRecord with all its elements, such as result_array and remaining_elements_count, which are not used by the Promise.race implementation:

pub struct PromiseGroupRecord<'a> {
    pub(crate) promise_group_type: PromiseGroupType,
    pub(crate) remaining_elements_count: u32,
    pub(crate) result_array: Array<'a>,
    pub(crate) promise: Promise<'a>,
}

We can keep it like this, or I can create a data structure specially for Promise.race that doesn't have any unused fields. This means also creating heap vectors to hold a PromiseRaceRecord struct. What do you prefer?

Hmm.... Do we actually need any kind of PromiseGroup at all...? Or can we just use the normal PromiseResolve stuff?

[komyg]

Hmm.... Do we actually need any kind of PromiseGroup at all...? Or can we just use the normal PromiseResolve stuff?

Well, I used the PromiseGroup, because the initial part of the spec is exactly the same for Promise.all, Promise.any, Promise.allSettled and Promise.race. Plus, all of them take in an iterable as an argument.

The difference is in the Perform Promise Race method, that doesn't use all the state that the other methods use. Even so, I am also using the immediately_resolve and immediatelly_reject functions from the PromiseGroup.

So if we can accept a slight more memory usage for Promise.race, I think we can continue as is.

As for the Promise.Resolve, I am not sure. The difference here is that Promise.race takes an array of promises, which is currently handled by PromiseGroup, and the Promise.Resolve will take a single value.

[aapoalas]

What I mean is that when you wrote your very first attempt at implementing Promise.all, you did it without any PromiseGroup or anything. You were simply chaining promises together using promise_inner_then or something like that. It seems that here, that would not only be functional but also exactly correct.

[komyg]

What I mean is that when you wrote your very first attempt at implementing Promise.all, you did it without any PromiseGroup or anything. You were simply chaining promises together using promise_inner_then or something like that. It seems that here, that would not only be functional but also exactly correct.

I think I understand.

I made another attempt here: #889, without using the promise_group.