Potential deadlock when using ImmediateScheduler

[orj]

I was running your package past our resident Combine expert and they mentioned:

It uses a single lock for downstream / upstream comms, so there are a number of scenarios that could result in deadlock. My guess it is doesn't support and hasn't been tested with the ImmediateScheduler. Thats generally a surefire way to find bugs with custom scheduling publishers.

I've not run any tests myself but thought I'd leave this feedback.

Hope it helps.

[elfenlaid]

Oh, that's for reaching out with the feedback 🙇

I've tested it with the ImmediateScheduler and the library seems to do fine. I wonder maybe it's something wrong with my test snippet?

import RateLimiter
import CombineSchedulers
import Combine

var cancellables = Set<AnyCancellable>()
defer { cancellables.removeAll() }

let scheduler = DispatchQueue.immediateScheduler
let strategy = QueueThroughputStrategy(rate: UInt(2), interval: .seconds(1), scheduler: scheduler)

var values: [Int] = []

(1...5).publisher
    .rateLimited(by: strategy)
    .sink(receiveValue: {
        values.append($0)
    })
    .store(in: &cancellables)

I just tweaked the snipped in the project's playground. You can clone the repo, open it with xed . and find the playground at Playgrounds > RateLimiter

CombineSchedulers is a library from https://github.com/pointfreeco/combine-schedulers which is really awesome, certainly worth having a look 👍

UPD:
You might also want to check my blog post about the library, more precisely about some assumptions it takes https://thegoodalright.dev/posts/combine-rate-limiting/#here-be-dragons