Revisit main actor isolation in the UI Process

8 files changed, 25 insertions, 37 deletions

diff --git a/ios/MullvadVPN/Coordinators/ApplicationCoordinator.swift b/ios/MullvadVPN/Coordinators/ApplicationCoordinator.swift
index 2175835045..6c0c61b5a2 100644
--- a/ios/MullvadVPN/Coordinators/ApplicationCoordinator.swift
+++ b/ios/MullvadVPN/Coordinators/ApplicationCoordinator.swift
@@ -450,14 +450,10 @@ final class ApplicationCoordinator: Coordinator, Presenting, @preconcurrency Roo
         coordinator.preferredAccountNumberPublisher = preferredAccountNumberSubject.eraseToAnyPublisher()
 
         coordinator.didFinish = { [weak self] _ in
-            MainActor.assumeIsolated {
-                self?.continueFlow(animated: true)
-            }
+            self?.continueFlow(animated: true)
         }
         coordinator.didCreateAccount = { [weak self] in
-            MainActor.assumeIsolated {
-                self?.appPreferences.isShownOnboarding = false
-            }
+            self?.appPreferences.isShownOnboarding = false
         }
 
         addChild(coordinator)
@@ -538,9 +534,7 @@ final class ApplicationCoordinator: Coordinator, Presenting, @preconcurrency Roo
         )
 
         coordinator.didFinish = { [weak self] _, reason in
-            MainActor.assumeIsolated {
-                self?.didDismissAccount(reason)
-            }
+            self?.didDismissAccount(reason)
         }
 
         coordinator.start(animated: animated)
diff --git a/ios/MullvadVPN/Coordinators/LoginCoordinator.swift b/ios/MullvadVPN/Coordinators/LoginCoordinator.swift
index 4ac34bcbbe..c6934df365 100644
--- a/ios/MullvadVPN/Coordinators/LoginCoordinator.swift
+++ b/ios/MullvadVPN/Coordinators/LoginCoordinator.swift
@@ -21,8 +21,8 @@ final class LoginCoordinator: Coordinator, Presenting, @preconcurrency DeviceMan
     nonisolated(unsafe) private var lastLoginAction: LoginAction?
     private var subscriptions = Set<Combine.AnyCancellable>()
 
-    var didFinish: (@Sendable (LoginCoordinator) -> Void)?
-    var didCreateAccount: (@Sendable () -> Void)?
+    var didFinish: (@MainActor @Sendable (LoginCoordinator) -> Void)?
+    var didCreateAccount: (@MainActor @Sendable () -> Void)?
 
     var preferredAccountNumberPublisher: AnyPublisher<String, Never>?
     var presentationContext: UIViewController {
diff --git a/ios/MullvadVPN/View controllers/Account/AccountViewController.swift b/ios/MullvadVPN/View controllers/Account/AccountViewController.swift
index 0c7ca21532..19060381ab 100644
--- a/ios/MullvadVPN/View controllers/Account/AccountViewController.swift
+++ b/ios/MullvadVPN/View controllers/Account/AccountViewController.swift
@@ -161,6 +161,8 @@ class AccountViewController: UIViewController, @unchecked Sendable {
             let productState: ProductState = completion.value?.products.first
                 .map { .received($0) } ?? .failed
 
+            /// `@MainActor` isolation is safe here because
+            /// `ProductsRequestOperation` sets its `completionQueue` to `.main`
             MainActor.assumeIsolated {
                 self?.setProductState(productState, animated: true)
             }
diff --git a/ios/MullvadVPN/View controllers/Account/PaymentAlertPresenter.swift b/ios/MullvadVPN/View controllers/Account/PaymentAlertPresenter.swift
index 4e62d1a808..07369ac526 100644
--- a/ios/MullvadVPN/View controllers/Account/PaymentAlertPresenter.swift
+++ b/ios/MullvadVPN/View controllers/Account/PaymentAlertPresenter.swift
@@ -16,7 +16,7 @@ struct PaymentAlertPresenter {
     func showAlertForError(
         _ error: StorePaymentManagerError,
         context: REST.CreateApplePaymentResponse.Context,
-        completion: (@Sendable () -> Void)? = nil
+        completion: (@MainActor @Sendable () -> Void)? = nil
     ) {
         let presentation = AlertPresentation(
             id: "payment-error-alert",
@@ -64,7 +64,7 @@ struct PaymentAlertPresenter {
     func showAlertForResponse(
         _ response: REST.CreateApplePaymentResponse,
         context: REST.CreateApplePaymentResponse.Context,
-        completion: (@Sendable () -> Void)? = nil
+        completion: (@MainActor @Sendable () -> Void)? = nil
     ) {
         guard case .noTimeAdded = response else {
             completion?()
diff --git a/ios/MullvadVPN/View controllers/Login/LoginInteractor.swift b/ios/MullvadVPN/View controllers/Login/LoginInteractor.swift
index cd7564f356..302f1fa30c 100644
--- a/ios/MullvadVPN/View controllers/Login/LoginInteractor.swift
+++ b/ios/MullvadVPN/View controllers/Login/LoginInteractor.swift
@@ -14,7 +14,7 @@ final class LoginInteractor: @unchecked Sendable {
     private let tunnelManager: TunnelManager
     private let logger = Logger(label: "LoginInteractor")
     private var tunnelObserver: TunnelObserver?
-    var didCreateAccount: (@Sendable () -> Void)?
+    var didCreateAccount: (@MainActor @Sendable () -> Void)?
     var suggestPreferredAccountNumber: (@Sendable (String) -> Void)?
 
     init(tunnelManager: TunnelManager) {
@@ -27,7 +27,7 @@ final class LoginInteractor: @unchecked Sendable {
 
     func createAccount() async throws -> String {
         let accountNumber = try await tunnelManager.setNewAccount().number
-        didCreateAccount?()
+        await didCreateAccount?()
 
         return accountNumber
     }
diff --git a/ios/MullvadVPN/View controllers/OutOfTime/OutOfTimeViewController.swift b/ios/MullvadVPN/View controllers/OutOfTime/OutOfTimeViewController.swift
index a735fb4eca..5f26cd4643 100644
--- a/ios/MullvadVPN/View controllers/OutOfTime/OutOfTimeViewController.swift
+++ b/ios/MullvadVPN/View controllers/OutOfTime/OutOfTimeViewController.swift
@@ -221,9 +221,7 @@ class OutOfTimeViewController: UIViewController, RootContainment {
 
             default:
                 errorPresenter.showAlertForError(paymentFailure.error, context: .purchase) {
-                    MainActor.assumeIsolated {
-                        self.paymentState = .none
-                    }
+                    self.paymentState = .none
                 }
             }
         }
@@ -253,30 +251,23 @@ class OutOfTimeViewController: UIViewController, RootContainment {
 
         paymentState = .restoringPurchases
 
+        /// Safe to assume `@MainActor` isolation because `SendStoreReceiptOperation` sets both its
+        /// `dispatchQueue` and `completionQueue` to `.main`
         _ = interactor.restorePurchases(for: accountData.number) { [weak self] result in
             guard let self else { return }
-
-            switch result {
-            case let .success(response):
-                Task { @MainActor in
+            MainActor.assumeIsolated {
+                switch result {
+                case let .success(response):
                     errorPresenter.showAlertForResponse(response, context: .restoration) {
-                        MainActor.assumeIsolated {
-                            self.paymentState = .none
-                        }
+                        self.paymentState = .none
                     }
-                }
 
-            case let .failure(error as StorePaymentManagerError):
-                Task { @MainActor in
+                case let .failure(error as StorePaymentManagerError):
                     errorPresenter.showAlertForError(error, context: .restoration) {
-                        MainActor.assumeIsolated {
-                            self.paymentState = .none
-                        }
+                        self.paymentState = .none
                     }
-                }
 
-            default:
-                Task { @MainActor in
+                default:
                     paymentState = .none
                 }
             }
diff --git a/ios/MullvadVPN/View controllers/RedeemVoucher/RedeemVoucherViewController.swift b/ios/MullvadVPN/View controllers/RedeemVoucher/RedeemVoucherViewController.swift
index 870426c004..c62dc917ef 100644
--- a/ios/MullvadVPN/View controllers/RedeemVoucher/RedeemVoucherViewController.swift
+++ b/ios/MullvadVPN/View controllers/RedeemVoucher/RedeemVoucherViewController.swift
@@ -116,6 +116,8 @@ class RedeemVoucherViewController: UIViewController, UINavigationControllerDeleg
         contentView.isEditing = false
         interactor.redeemVoucher(code: code, completion: { [weak self] result in
             guard let self else { return }
+            /// Safe to assume `@MainActor` isolation because
+            /// `TunnelManager.redeemVoucher` sets the `RedeemVoucherOperation`'s `completionQueue` to `.main`
             MainActor.assumeIsolated {
                 switch result {
                 case let .success(value):
diff --git a/ios/Routing/Router/ApplicationRouter.swift b/ios/Routing/Router/ApplicationRouter.swift
index c55daf2400..0baa0662dd 100644
--- a/ios/Routing/Router/ApplicationRouter.swift
+++ b/ios/Routing/Router/ApplicationRouter.swift
@@ -158,9 +158,8 @@ public final class ApplicationRouter<RouteType: AppRouteProtocol>: Sendable {
             let context = RoutePresentationContext(route: route, isAnimated: animated, metadata: metadata)
 
             delegate.applicationRouter(self, presentWithContext: context, animated: animated) { coordinator in
-                /*
-                 Synchronize router when modal controllers are removed by swipe.
-                 */
+                /// Synchronize router when modal controllers are removed by swipe.
+                /// The delegate (`ApplicationCoordinator`) is `@MainActor` by virtue of being a `Coordinator`
                 MainActor.assumeIsolated {
                     if let presentable = coordinator as? Presentable {
                         presentable.onInteractiveDismissal { [weak self] coordinator in