[BUG] ApplePayContextDelegate completions aren't sendable

[blsage]

Summary

When you try to await your client secret within your applePayContext delegate function, you receive an error regarding Sendable:

Passing closure as a 'sending' parameter risks causing data races between code in the current task and concurrent execution of the closure; this is an error in the Swift 6 language model
Closure captures 'completion' which is accessible to code in the current task

Code to reproduce

    func applePayContext(
        _ context: STPApplePayContext,
        didCreatePaymentMethod paymentMethod: StripeAPI.PaymentMethod,
        paymentInformation: PKPayment,
        completion: @escaping STPIntentClientSecretCompletionBlock
    ) {
        let contribution = self.contribution
        Task {
            do {
                let clientSecret = try await contribution.clientSecret
                completion(clientSecret, nil) // <- Here
            } catch {
                completion(nil, error)
            }
        }
    }

iOS version

18.1.1

Installation method

SPM

SDK version

Stripe 24.1.0

[tjclawson-stripe]

Hi @blsage thanks for reporting, we'll look into this

[porter-stripe]

HI @blsage, can you try to call the completion handler on the MainActor? Maybe something like this

func applePayContext(
    _ context: STPApplePayContext,
    didCreatePaymentMethod paymentMethod: StripeAPI.PaymentMethod,
    paymentInformation: PKPayment,
    completion: @escaping STPIntentClientSecretCompletionBlock
) {
    let contribution = self.contribution
    Task {
        do {
            let clientSecret = try await contribution.clientSecret
            
            // Switch explicitly to the main actor
            await MainActor.run {
                completion(clientSecret, nil)
            }
        } catch {
            // Switch to the main actor for completion as well
            await MainActor.run {
                completion(nil, error)
            }
        }
    }
}

[blsage]

Tried all variations of that. The fundamental problem is that you need to make the completion be sendable or you can't send it to the main actor.

[blsage]

But maybe it's best to triage this issue until you migrate the whole API to async/await and swift 6? Seems a bit like trying to fit a square peg into a round hole.

[blsage]

My ultimate solution was to create a sendable wrapper class and initialize it with the completion as a let parameter. Very hacky but removed the warnings.