fix(#2553) : AsyncSequence.asObservable() runs on background thread

[suojae]

Fixes #2553

Problem Description

The current implementation of AsyncSequence.asObservable() can potentially execute on the main thread, which may cause UI blocking issues. This becomes especially problematic when the AsyncSequence performs time-consuming operations.

Changes

Modified AsyncSequence.asObservable() to use Task.detached, ensuring the sequence always runs on a background thread. This change guarantees that AsyncSequence operations won't block the main thread.

Testing

• Successfully passed all existing tests
• Added and passed test cases that verify execution on background threads
• Included additional test cases covering edge scenarios (with sleep operations, error handling)

[hoc081098]

What do you think about adding a new param to decide whether to use Task or Task.detached?

[suojae]

I think adding a parameter is a good idea to provide flexibility. I'm considering implementing it like this:

func asObservable(detached: Bool = true) -> Observable<Element> {
    // Use Task.detached or Task based on the parameter
}

With true as the default value, it would still solve the original issue by running on a background thread, while giving users the option to use regular Task when they want to maintain the current context's priority.

What do you think about this approach and the default value being true?

[hoc081098]

It sounds good. I’ve also seen a similar implementation in another library, which takes the same approach

RxSwift/RxSwift/Traits/PrimitiveSequence/PrimitiveSequence+Concurrency.swift

Line 25 in 5dd1907

detached: Bool = false,

About the default value of detached, I think false should be used to avoid introducing a breaking change.

[suojae]

I've implemented the parameter as suggested, with false as the default value to maintain backward compatibility.

func asObservable(detached: Bool = false) -> Observable<Element> {
    // Implementation uses Task.detached when detached=true, otherwise uses Task
}

All tests are passing. Thanks!

[hoc081098]

Nice 🙏