Replace OperationCompletion with Result

Error is set to OperationError.cancelled if operation is cancelled.

49 files changed, 460 insertions, 637 deletions

diff --git a/ios/MullvadREST/RESTAccessTokenManager.swift b/ios/MullvadREST/RESTAccessTokenManager.swift
index 5a9dba1a52..d8d7ef5521 100644
--- a/ios/MullvadREST/RESTAccessTokenManager.swift
+++ b/ios/MullvadREST/RESTAccessTokenManager.swift
@@ -25,37 +25,36 @@ extension REST {
 
         func getAccessToken(
             accountNumber: String,
-            completionHandler: @escaping (OperationCompletion<REST.AccessTokenData, REST.Error>)
-                -> Void
+            completionHandler: @escaping (Result<REST.AccessTokenData, Swift.Error>) -> Void
         ) -> Cancellable {
-            let operation = ResultBlockOperation<REST.AccessTokenData, REST.Error>(
-                dispatchQueue: dispatchQueue
-            ) { operation in
+            let operation = ResultBlockOperation<REST.AccessTokenData>(dispatchQueue: dispatchQueue)
+
+            operation.setExecutionBlock { operation in
                 if let tokenData = self.tokens[accountNumber], tokenData.expiry > Date() {
-                    operation.finish(completion: .success(tokenData))
+                    operation.finish(result: .success(tokenData))
                     return
                 }
 
                 let task = self.proxy.getAccessToken(
                     accountNumber: accountNumber,
                     retryStrategy: .noRetry
-                ) { completion in
+                ) { result in
                     self.dispatchQueue.async {
-                        switch completion {
+                        switch result {
                         case let .success(tokenData):
                             self.tokens[accountNumber] = tokenData
 
-                        case let .failure(error):
+                        case let .failure(error) where !error.isOperationCancellationError:
                             self.logger.error(
                                 error: error,
                                 message: "Failed to fetch access token."
                             )
 
-                        case .cancelled:
+                        default:
                             break
                         }
 
-                        operation.finish(completion: completion)
+                        operation.finish(result: result)
                     }
                 }
 
diff --git a/ios/MullvadREST/RESTAuthorization.swift b/ios/MullvadREST/RESTAuthorization.swift
index c75a20f8cd..cce6e23f1f 100644
--- a/ios/MullvadREST/RESTAuthorization.swift
+++ b/ios/MullvadREST/RESTAuthorization.swift
@@ -11,9 +11,8 @@ import MullvadTypes
 import Operations
 
 protocol RESTAuthorizationProvider {
-    typealias Completion = OperationCompletion<REST.Authorization, REST.Error>
-
-    func getAuthorization(completion: @escaping (Completion) -> Void) -> Cancellable
+    func getAuthorization(completion: @escaping (Result<REST.Authorization, Swift.Error>) -> Void)
+        -> Cancellable
 }
 
 extension REST {
@@ -28,13 +27,15 @@ extension REST {
             self.accountNumber = accountNumber
         }
 
-        func getAuthorization(completion: @escaping (Completion) -> Void) -> Cancellable {
-            return accessTokenManager
-                .getAccessToken(accountNumber: accountNumber) { operationCompletion in
-                    completion(operationCompletion.map { tokenData in
-                        return tokenData.accessToken
-                    })
-                }
+        func getAuthorization(
+            completion: @escaping (Result<REST.Authorization, Swift.Error>)
+                -> Void
+        ) -> Cancellable {
+            return accessTokenManager.getAccessToken(accountNumber: accountNumber) { result in
+                completion(result.map { tokenData in
+                    return tokenData.accessToken
+                })
+            }
         }
     }
 }
diff --git a/ios/MullvadREST/RESTNetworkOperation.swift b/ios/MullvadREST/RESTNetworkOperation.swift
index 9c8e0cbf2a..64f07a3e93 100644
--- a/ios/MullvadREST/RESTNetworkOperation.swift
+++ b/ios/MullvadREST/RESTNetworkOperation.swift
@@ -12,7 +12,7 @@ import MullvadTypes
 import Operations
 
 extension REST {
-    class NetworkOperation<Success>: ResultOperation<Success, REST.Error> {
+    class NetworkOperation<Success>: ResultOperation<Success> {
         private let requestHandler: RESTRequestHandler
         private let responseHandler: AnyResponseHandler<Success>
 
@@ -76,7 +76,7 @@ extension REST {
             dispatchPrecondition(condition: .onQueue(dispatchQueue))
 
             guard !isCancelled else {
-                finish(completion: .cancelled)
+                finish(result: .failure(OperationError.cancelled))
                 return
             }
 
@@ -87,17 +87,18 @@ extension REST {
             }
 
             requiresAuthorization = true
-            authorizationTask = authorizationProvider.getAuthorization { completion in
+            authorizationTask = authorizationProvider.getAuthorization { result in
                 self.dispatchQueue.async {
-                    switch completion {
+                    switch result {
                     case let .success(authorization):
                         self.didReceiveAuthorization(authorization)
 
                     case let .failure(error):
-                        self.didFailToRequestAuthorization(error)
-
-                    case .cancelled:
-                        self.finish(completion: .cancelled)
+                        if error.isOperationCancellationError {
+                            self.finish(result: .failure(error))
+                        } else {
+                            self.didFailToRequestAuthorization(error)
+                        }
                     }
                 }
             }
@@ -107,7 +108,7 @@ extension REST {
             dispatchPrecondition(condition: .onQueue(dispatchQueue))
 
             guard !isCancelled else {
-                finish(completion: .cancelled)
+                finish(result: .failure(OperationError.cancelled))
                 return
             }
 
@@ -125,7 +126,7 @@ extension REST {
             }
         }
 
-        private func didFailToRequestAuthorization(_ error: REST.Error) {
+        private func didFailToRequestAuthorization(_ error: Swift.Error) {
             dispatchPrecondition(condition: .onQueue(dispatchQueue))
 
             logger.error(
@@ -133,7 +134,7 @@ extension REST {
                 message: "Failed to request authorization."
             )
 
-            finish(completion: .failure(error))
+            finish(result: .failure(error))
         }
 
         private func didReceiveURLRequest(_ restRequest: REST.Request, endpoint: AnyIPEndpoint) {
@@ -141,7 +142,7 @@ extension REST {
 
             guard let transport = transportProvider() else {
                 logger.error("Failed to obtain transport.")
-                finish(completion: .failure(.transport(NoTransportError())))
+                finish(result: .failure(REST.Error.transport(NoTransportError())))
                 return
             }
 
@@ -190,7 +191,7 @@ extension REST {
                 message: "Failed to create URLRequest."
             )
 
-            finish(completion: .failure(error))
+            finish(result: .failure(error))
         }
 
         private func didReceiveError(
@@ -203,7 +204,7 @@ extension REST {
             if let urlError = error as? URLError {
                 switch urlError.code {
                 case .cancelled:
-                    finish(completion: .cancelled)
+                    finish(result: .failure(OperationError.cancelled))
                     return
 
                 case .notConnectedToInternet, .internationalRoamingOff, .callIsActive:
@@ -237,7 +238,7 @@ extension REST {
             switch handlerResult {
             case let .success(output):
                 // Response handler produced value.
-                finish(completion: .success(output))
+                finish(result: .success(output))
 
             case let .decoding(decoderBlock):
                 // Response handler returned a block decoding value.
@@ -245,7 +246,7 @@ extension REST {
                     .mapError { error -> REST.Error in
                         return .decodeResponse(error)
                     }
-                finish(completion: OperationCompletion(result: decodeResult))
+                finish(result: decodeResult.mapError { $0 })
 
             case let .unhandledResponse(serverErrorResponse):
                 // Response handler couldn't handle the response.
@@ -257,11 +258,9 @@ extension REST {
                     retryInvalidAccessTokenError = false
                     startRequest()
                 } else {
-                    finish(
-                        completion: .failure(
-                            .unhandledResponse(response.statusCode, serverErrorResponse)
-                        )
-                    )
+                    finish(result: .failure(
+                        REST.Error.unhandledResponse(response.statusCode, serverErrorResponse)
+                    ))
                 }
             }
         }
@@ -272,7 +271,7 @@ extension REST {
                 if retryStrategy.maxRetryCount > 0 {
                     logger.debug("Ran out of retry attempts (\(retryStrategy.maxRetryCount))")
                 }
-                finish(completion: .failure(wrapRequestError(error)))
+                finish(result: .failure(wrapRequestError(error)))
                 return
             }
 
@@ -288,7 +287,7 @@ extension REST {
             guard let waitDelay = retryDelayIterator.next() else {
                 logger.debug("Retry delay iterator failed to produce next value.")
 
-                finish(completion: .failure(wrapRequestError(error)))
+                finish(result: .failure(wrapRequestError(error)))
                 return
             }
 
@@ -302,7 +301,7 @@ extension REST {
             }
 
             timer.setCancelHandler { [weak self] in
-                self?.finish(completion: .cancelled)
+                self?.finish(result: .failure(OperationError.cancelled))
             }
 
             timer.schedule(wallDeadline: .now() + waitDelay.timeInterval)
diff --git a/ios/MullvadREST/RESTProxy.swift b/ios/MullvadREST/RESTProxy.swift
index fe9bf7386a..5c8a14df81 100644
--- a/ios/MullvadREST/RESTProxy.swift
+++ b/ios/MullvadREST/RESTProxy.swift
@@ -12,8 +12,7 @@ import Operations
 
 extension REST {
     public class Proxy<ConfigurationType: ProxyConfiguration> {
-        public typealias CompletionHandler<Success> = (OperationCompletion<Success, REST.Error>)
-            -> Void
+        public typealias CompletionHandler<Success> = (Result<Success, Swift.Error>) -> Void
 
         /// Synchronization queue used by network operations.
         let dispatchQueue: DispatchQueue
diff --git a/ios/MullvadVPN.xcodeproj/project.pbxproj b/ios/MullvadVPN.xcodeproj/project.pbxproj
index 6875501ade..a5bc1234df 100644
--- a/ios/MullvadVPN.xcodeproj/project.pbxproj
+++ b/ios/MullvadVPN.xcodeproj/project.pbxproj
@@ -248,10 +248,9 @@
 		58D223AF294C8A630029F5F8 /* NoFailedDependenciesCondition.swift in Sources */ = {isa = PBXBuildFile; fileRef = 581813A228E09DCD002817DE /* NoFailedDependenciesCondition.swift */; };
 		58D223B0294C8A630029F5F8 /* TransformOperation.swift in Sources */ = {isa = PBXBuildFile; fileRef = 58059DDB28465E8F002B1049 /* TransformOperation.swift */; };
 		58D223B1294C8A630029F5F8 /* OperationCondition.swift in Sources */ = {isa = PBXBuildFile; fileRef = 589D28772846250500F9A7B3 /* OperationCondition.swift */; };
-		58D223B2294C8A630029F5F8 /* OperationCompletion.swift in Sources */ = {isa = PBXBuildFile; fileRef = 5840BE34279EDB16002836BA /* OperationCompletion.swift */; };
+		58D223B2294C8A630029F5F8 /* OperationError.swift in Sources */ = {isa = PBXBuildFile; fileRef = 5840BE34279EDB16002836BA /* OperationError.swift */; };
 		58D223B3294C8A630029F5F8 /* OperationObserver.swift in Sources */ = {isa = PBXBuildFile; fileRef = 589D28792846250500F9A7B3 /* OperationObserver.swift */; };
 		58D223B4294C8A630029F5F8 /* InputInjectionBuilder.swift in Sources */ = {isa = PBXBuildFile; fileRef = 58DF5B752852108E00E92647 /* InputInjectionBuilder.swift */; };
-		58D223B5294C8A630029F5F8 /* ResultOperation+Output.swift in Sources */ = {isa = PBXBuildFile; fileRef = 58059DDF2846823E002B1049 /* ResultOperation+Output.swift */; };
 		58D223B6294C8A630029F5F8 /* BlockCondition.swift in Sources */ = {isa = PBXBuildFile; fileRef = 581813A428E09DE2002817DE /* BlockCondition.swift */; };
 		58D223B7294C8A630029F5F8 /* MutuallyExclusive.swift in Sources */ = {isa = PBXBuildFile; fileRef = 581813A628E09DF2002817DE /* MutuallyExclusive.swift */; };
 		58D223B8294C8A630029F5F8 /* ResultOperation.swift in Sources */ = {isa = PBXBuildFile; fileRef = 58F7D26427EB50A300E4D821 /* ResultOperation.swift */; };
@@ -643,7 +642,6 @@
 		5803B4B12940A48700C23744 /* TunnelStore.swift */ = {isa = PBXFileReference; lastKnownFileType = sourcecode.swift; path = TunnelStore.swift; sourceTree = "<group>"; };
 		58059DDB28465E8F002B1049 /* TransformOperation.swift */ = {isa = PBXFileReference; fileEncoding = 4; lastKnownFileType = sourcecode.swift; path = TransformOperation.swift; sourceTree = "<group>"; };
 		58059DDD28468158002B1049 /* OutputOperation.swift */ = {isa = PBXFileReference; lastKnownFileType = sourcecode.swift; path = OutputOperation.swift; sourceTree = "<group>"; };
-		58059DDF2846823E002B1049 /* ResultOperation+Output.swift */ = {isa = PBXFileReference; lastKnownFileType = sourcecode.swift; path = "ResultOperation+Output.swift"; sourceTree = "<group>"; };
 		5807E2BF2432038B00F5FF30 /* String+Split.swift */ = {isa = PBXFileReference; fileEncoding = 4; lastKnownFileType = sourcecode.swift; path = "String+Split.swift"; sourceTree = "<group>"; };
 		5807E2C1243203D000F5FF30 /* StringTests.swift */ = {isa = PBXFileReference; fileEncoding = 4; lastKnownFileType = sourcecode.swift; path = StringTests.swift; sourceTree = "<group>"; };
 		5808273928487E3E006B77A4 /* Base.xcconfig */ = {isa = PBXFileReference; lastKnownFileType = text.xcconfig; path = Base.xcconfig; sourceTree = "<group>"; };
@@ -694,7 +692,7 @@
 		583DA21325FA4B5C00318683 /* LocationDataSource.swift */ = {isa = PBXFileReference; lastKnownFileType = sourcecode.swift; path = LocationDataSource.swift; sourceTree = "<group>"; };
 		583E1E292848DF67004838B3 /* OperationObserverTests.swift */ = {isa = PBXFileReference; lastKnownFileType = sourcecode.swift; path = OperationObserverTests.swift; sourceTree = "<group>"; };
 		5840250322B11AB700E4CFEC /* MullvadEndpoint.swift */ = {isa = PBXFileReference; lastKnownFileType = sourcecode.swift; path = MullvadEndpoint.swift; sourceTree = "<group>"; };
-		5840BE34279EDB16002836BA /* OperationCompletion.swift */ = {isa = PBXFileReference; lastKnownFileType = sourcecode.swift; path = OperationCompletion.swift; sourceTree = "<group>"; };
+		5840BE34279EDB16002836BA /* OperationError.swift */ = {isa = PBXFileReference; lastKnownFileType = sourcecode.swift; path = OperationError.swift; sourceTree = "<group>"; };
 		5842102D282D3FC200F24E46 /* ResultBlockOperation.swift */ = {isa = PBXFileReference; lastKnownFileType = sourcecode.swift; path = ResultBlockOperation.swift; sourceTree = "<group>"; };
 		5842102F282D8A3C00F24E46 /* UpdateAccountDataOperation.swift */ = {isa = PBXFileReference; lastKnownFileType = sourcecode.swift; path = UpdateAccountDataOperation.swift; sourceTree = "<group>"; };
 		58421031282E42B000F24E46 /* UpdateDeviceDataOperation.swift */ = {isa = PBXFileReference; lastKnownFileType = sourcecode.swift; path = UpdateDeviceDataOperation.swift; sourceTree = "<group>"; };
@@ -1545,13 +1543,12 @@
 				581813A628E09DF2002817DE /* MutuallyExclusive.swift */,
 				581813A028E09DBB002817DE /* NoCancelledDependenciesCondition.swift */,
 				581813A228E09DCD002817DE /* NoFailedDependenciesCondition.swift */,
-				5840BE34279EDB16002836BA /* OperationCompletion.swift */,
+				5840BE34279EDB16002836BA /* OperationError.swift */,
 				589D28772846250500F9A7B3 /* OperationCondition.swift */,
 				589D28792846250500F9A7B3 /* OperationObserver.swift */,
 				58059DDD28468158002B1049 /* OutputOperation.swift */,
 				5842102D282D3FC200F24E46 /* ResultBlockOperation.swift */,
 				58F7D26427EB50A300E4D821 /* ResultOperation.swift */,
-				58059DDF2846823E002B1049 /* ResultOperation+Output.swift */,
 				58059DDB28465E8F002B1049 /* TransformOperation.swift */,
 			);
 			path = Operations;
@@ -2503,12 +2500,11 @@
 				58D223B6294C8A630029F5F8 /* BlockCondition.swift in Sources */,
 				58D223BA294C8A630029F5F8 /* BackgroundObserver.swift in Sources */,
 				58D223AD294C8A630029F5F8 /* AsyncBlockOperation.swift in Sources */,
-				58D223B5294C8A630029F5F8 /* ResultOperation+Output.swift in Sources */,
 				58D223AC294C8A630029F5F8 /* GroupOperation.swift in Sources */,
 				58D223BB294C8A630029F5F8 /* NoCancelledDependenciesCondition.swift in Sources */,
 				58D223B3294C8A630029F5F8 /* OperationObserver.swift in Sources */,
 				58D223B7294C8A630029F5F8 /* MutuallyExclusive.swift in Sources */,
-				58D223B2294C8A630029F5F8 /* OperationCompletion.swift in Sources */,
+				58D223B2294C8A630029F5F8 /* OperationError.swift in Sources */,
 				58D223AF294C8A630029F5F8 /* NoFailedDependenciesCondition.swift in Sources */,
 				58D223B9294C8A630029F5F8 /* AsyncOperationQueue.swift in Sources */,
 				58D223B8294C8A630029F5F8 /* ResultOperation.swift in Sources */,
diff --git a/ios/MullvadVPN/AccountInteractor.swift b/ios/MullvadVPN/AccountInteractor.swift
index 8444a426db..c454181d95 100644
--- a/ios/MullvadVPN/AccountInteractor.swift
+++ b/ios/MullvadVPN/AccountInteractor.swift
@@ -56,10 +56,7 @@ final class AccountInteractor {
 
     func restorePurchases(
         for accountNumber: String,
-        completionHandler: @escaping (OperationCompletion<
-            REST.CreateApplePaymentResponse,
-            StorePaymentManagerError
-        >) -> Void
+        completionHandler: @escaping (Result<REST.CreateApplePaymentResponse, Error>) -> Void
     ) -> Cancellable {
         return storePaymentManager.restorePurchases(
             for: accountNumber,
@@ -69,7 +66,7 @@ final class AccountInteractor {
 
     func requestProducts(
         with productIdentifiers: Set<StoreSubscription>,
-        completionHandler: @escaping (OperationCompletion<SKProductsResponse, Error>) -> Void
+        completionHandler: @escaping (Result<SKProductsResponse, Error>) -> Void
     ) -> Cancellable {
         return storePaymentManager.requestProducts(
             with: productIdentifiers,
diff --git a/ios/MullvadVPN/AccountViewController.swift b/ios/MullvadVPN/AccountViewController.swift
index 1d4b82b56e..34f16b3233 100644
--- a/ios/MullvadVPN/AccountViewController.swift
+++ b/ios/MullvadVPN/AccountViewController.swift
@@ -329,10 +329,10 @@ class AccountViewController: UIViewController {
             case let .success(response):
                 self.showTimeAddedConfirmationAlert(with: response, context: .restoration)
 
-            case let .failure(error):
+            case let .failure(error as StorePaymentManagerError):
                 self.showRestorePurchasesErrorAlert(error: error)
 
-            case .cancelled:
+            default:
                 break
             }
 
diff --git a/ios/MullvadVPN/AddressCacheTracker.swift b/ios/MullvadVPN/AddressCacheTracker.swift
index 7fb0e79826..8c3100f92b 100644
--- a/ios/MullvadVPN/AddressCacheTracker.swift
+++ b/ios/MullvadVPN/AddressCacheTracker.swift
@@ -84,22 +84,17 @@ final class AddressCacheTracker {
         timer = nil
     }
 
-    func updateEndpoints(
-        completionHandler: ((OperationCompletion<Bool, Error>) -> Void)? = nil
-    ) -> Cancellable {
-        let operation = ResultBlockOperation<Bool, Error> { operation in
+    func updateEndpoints(completionHandler: ((Result<Bool, Error>) -> Void)? = nil) -> Cancellable {
+        let operation = ResultBlockOperation<Bool> { operation in
             guard self.nextScheduleDate() <= Date() else {
-                operation.finish(completion: .success(false))
+                operation.finish(result: .success(false))
                 return
             }
 
-            let task = self.apiProxy.getAddressList(retryStrategy: .default) { completion in
-                self.setEndpoints(from: completion)
+            let task = self.apiProxy.getAddressList(retryStrategy: .default) { result in
+                self.setEndpoints(from: result)
 
-                let mappedCompletion = completion.map { _ in true }
-                    .eraseFailureType()
-
-                operation.finish(completion: mappedCompletion)
+                operation.finish(result: result.map { _ in true })
             }
 
             operation.addCancellationBlock {
@@ -130,25 +125,25 @@ final class AddressCacheTracker {
         return _nextScheduleDate()
     }
 
-    private func setEndpoints(from completion: OperationCompletion<[AnyIPEndpoint], REST.Error>) {
+    private func setEndpoints(from result: Result<[AnyIPEndpoint], Error>) {
         nslock.lock()
         defer { nslock.unlock() }
 
-        switch completion {
+        switch result {
         case let .success(endpoints):
             store.setEndpoints(endpoints)
+            lastFailureAttemptDate = nil
 
-        case let .failure(error):
+        case let .failure(error as REST.Error):
             logger.error(
                 error: error,
                 message: "Failed to update address cache."
             )
+            fallthrough
 
-        case .cancelled:
-            break
+        default:
+            lastFailureAttemptDate = Date()
         }
-
-        lastFailureAttemptDate = completion.isSuccess ? nil : Date()
     }
 
     private func scheduleEndpointsUpdate(startTime: DispatchWallTime) {
diff --git a/ios/MullvadVPN/AppDelegate.swift b/ios/MullvadVPN/AppDelegate.swift
index 89b9b505f2..3ed73a43fa 100644
--- a/ios/MullvadVPN/AppDelegate.swift
+++ b/ios/MullvadVPN/AppDelegate.swift
@@ -209,10 +209,10 @@ class AppDelegate: UIResponder, UIApplicationDelegate, UNUserNotificationCenterD
             forTaskWithIdentifier: ApplicationConfiguration.addressCacheUpdateTaskIdentifier,
             using: nil
         ) { task in
-            let handle = self.addressCacheTracker.updateEndpoints { completion in
+            let handle = self.addressCacheTracker.updateEndpoints { result in
                 self.scheduleAddressCacheUpdateTask()
 
-                task.setTaskCompleted(success: completion.isSuccess)
+                task.setTaskCompleted(success: result.isSuccess)
             }
 
             task.expirationHandler = {
@@ -373,12 +373,12 @@ class AppDelegate: UIResponder, UIApplicationDelegate, UNUserNotificationCenterD
             }
         }
 
-        let migrateSettingsOperation = ResultBlockOperation<SettingsMigrationResult, Error>(
+        let migrateSettingsOperation = ResultBlockOperation<SettingsMigrationResult>(
             dispatchQueue: .main
         ) { operation in
             SettingsManager.migrateStore(with: self.proxyFactory) { migrationResult in
                 let finishHandler = {
-                    operation.finish(completion: .success(migrationResult))
+                    operation.finish(result: .success(migrationResult))
                 }
 
                 guard case let .failure(error) = migrationResult,
@@ -412,7 +412,7 @@ class AppDelegate: UIResponder, UIApplicationDelegate, UNUserNotificationCenterD
         }
         initTunnelManagerOperation.addDependency(migrateSettingsOperation)
 
-        let reconnectTunnelOperation = TransformOperation<SettingsMigrationResult, Void, Error>(
+        let reconnectTunnelOperation = TransformOperation<SettingsMigrationResult, Void>(
             dispatchQueue: .main
         ) { migrationResult in
             if case .success = migrationResult {
diff --git a/ios/MullvadVPN/DeviceManagementInteractor.swift b/ios/MullvadVPN/DeviceManagementInteractor.swift
index 87ee7f204a..7aa202a2cd 100644
--- a/ios/MullvadVPN/DeviceManagementInteractor.swift
+++ b/ios/MullvadVPN/DeviceManagementInteractor.swift
@@ -22,28 +22,26 @@ class DeviceManagementInteractor {
 
     @discardableResult
     func getDevices(
-        _ completionHandler: @escaping (OperationCompletion<[REST.Device], Error>)
+        _ completionHandler: @escaping (Result<[REST.Device], Error>)
             -> Void
     ) -> Cancellable {
         return devicesProxy.getDevices(
             accountNumber: accountNumber,
-            retryStrategy: .default
-        ) { completion in
-            completionHandler(completion.eraseFailureType())
-        }
+            retryStrategy: .default,
+            completion: completionHandler
+        )
     }
 
     @discardableResult
     func deleteDevice(
         _ identifier: String,
-        completionHandler: @escaping (OperationCompletion<Bool, Error>) -> Void
+        completionHandler: @escaping (Result<Bool, Error>) -> Void
     ) -> Cancellable {
         return devicesProxy.deleteDevice(
             accountNumber: accountNumber,
             identifier: identifier,
-            retryStrategy: .default
-        ) { completion in
-            completionHandler(completion.eraseFailureType())
-        }
+            retryStrategy: .default,
+            completion: completionHandler
+        )
     }
 }
diff --git a/ios/MullvadVPN/DeviceManagementViewController.swift b/ios/MullvadVPN/DeviceManagementViewController.swift
index d96d9172fd..d3b0d006da 100644
--- a/ios/MullvadVPN/DeviceManagementViewController.swift
+++ b/ios/MullvadVPN/DeviceManagementViewController.swift
@@ -85,16 +85,16 @@ class DeviceManagementViewController: UIViewController, RootContainment {
 
     func fetchDevices(
         animateUpdates: Bool,
-        completionHandler: ((OperationCompletion<Void, Error>) -> Void)? = nil
+        completionHandler: ((Result<Void, Error>) -> Void)? = nil
     ) {
-        interactor.getDevices { [weak self] completion in
+        interactor.getDevices { [weak self] result in
             guard let self = self else { return }
 
-            if let devices = completion.value {
+            if let devices = result.value {
                 self.setDevices(devices, animated: animateUpdates)
             }
 
-            completionHandler?(completion.ignoreOutput())
+            completionHandler?(result.map { _ in () })
         }
     }
 
@@ -236,14 +236,15 @@ class DeviceManagementViewController: UIViewController, RootContainment {
                 }
 
             case let .failure(error):
-                self.logger.error(
-                    error: error,
-                    message: "Failed to delete device."
-                )
-                completionHandler(error)
-
-            case .cancelled:
-                completionHandler(nil)
+                if error.isOperationCancellationError {
+                    completionHandler(nil)
+                } else {
+                    self.logger.error(
+                        error: error,
+                        message: "Failed to delete device."
+                    )
+                    completionHandler(error)
+                }
             }
         }
     }
diff --git a/ios/MullvadVPN/LoginViewController.swift b/ios/MullvadVPN/LoginViewController.swift
index a0c13358a3..ed113160e9 100644
--- a/ios/MullvadVPN/LoginViewController.swift
+++ b/ios/MullvadVPN/LoginViewController.swift
@@ -36,7 +36,7 @@ protocol LoginViewControllerDelegate: AnyObject {
     func loginViewController(
         _ controller: LoginViewController,
         shouldHandleLoginAction action: LoginAction,
-        completion: @escaping (OperationCompletion<StoredAccountData?, Error>) -> Void
+        completion: @escaping (Result<StoredAccountData?, Error>) -> Void
     )
 
     func loginViewControllerDidFinishLogin(_ controller: LoginViewController)
@@ -184,9 +184,7 @@ class LoginViewController: UIViewController, RootContainment {
 
                     self?.endLogin(.success(action))
                 case let .failure(error):
-                    self?.endLogin(.failure(error))
-                case .cancelled:
-                    self?.endLogin(.default)
+                    self?.endLogin(error.isOperationCancellationError ? .default : .failure(error))
                 }
             }
     }
diff --git a/ios/MullvadVPN/Operations/ProductsRequestOperation.swift b/ios/MullvadVPN/Operations/ProductsRequestOperation.swift
index f9ddb09f72..380dc5267e 100644
--- a/ios/MullvadVPN/Operations/ProductsRequestOperation.swift
+++ b/ios/MullvadVPN/Operations/ProductsRequestOperation.swift
@@ -9,7 +9,7 @@
 import Operations
 import StoreKit
 
-public final class ProductsRequestOperation: ResultOperation<SKProductsResponse, Error>,
+public final class ProductsRequestOperation: ResultOperation<SKProductsResponse>,
     SKProductsRequestDelegate
 {
     private let productIdentifiers: Set<String>
@@ -52,7 +52,7 @@ public final class ProductsRequestOperation: ResultOperation<SKProductsResponse,
                 self.retryCount += 1
                 self.retry(error: error)
             } else {
-                self.finish(completion: .failure(error))
+                self.finish(result: .failure(error))
             }
         }
     }
@@ -61,7 +61,7 @@ public final class ProductsRequestOperation: ResultOperation<SKProductsResponse,
         _ request: SKProductsRequest,
         didReceive response: SKProductsResponse
     ) {
-        finish(completion: .success(response))
+        finish(result: .success(response))
     }
 
     // MARK: - Private
@@ -80,7 +80,7 @@ public final class ProductsRequestOperation: ResultOperation<SKProductsResponse,
         }
 
         retryTimer?.setCancelHandler { [weak self] in
-            self?.finish(completion: .failure(error))
+            self?.finish(result: .failure(error))
         }
 
         retryTimer?.schedule(wallDeadline: .now() + retryDelay)
diff --git a/ios/MullvadVPN/OutOfTimeInteractor.swift b/ios/MullvadVPN/OutOfTimeInteractor.swift
index cd4989461a..4166cb1e36 100644
--- a/ios/MullvadVPN/OutOfTimeInteractor.swift
+++ b/ios/MullvadVPN/OutOfTimeInteractor.swift
@@ -61,9 +61,9 @@ final class OutOfTimeInteractor {
 
     func restorePurchases(
         for accountNumber: String,
-        completionHandler: @escaping (OperationCompletion<
+        completionHandler: @escaping (Result<
             REST.CreateApplePaymentResponse,
-            StorePaymentManagerError
+            Error
         >) -> Void
     ) -> Cancellable {
         return storePaymentManager.restorePurchases(
@@ -74,7 +74,7 @@ final class OutOfTimeInteractor {
 
     func requestProducts(
         with productIdentifiers: Set<StoreSubscription>,
-        completionHandler: @escaping (OperationCompletion<SKProductsResponse, Error>) -> Void
+        completionHandler: @escaping (Result<SKProductsResponse, Error>) -> Void
     ) -> Cancellable {
         return storePaymentManager.requestProducts(
             with: productIdentifiers,
diff --git a/ios/MullvadVPN/OutOfTimeViewController.swift b/ios/MullvadVPN/OutOfTimeViewController.swift
index ac8c021bd3..70f7ea57bc 100644
--- a/ios/MullvadVPN/OutOfTimeViewController.swift
+++ b/ios/MullvadVPN/OutOfTimeViewController.swift
@@ -301,17 +301,17 @@ class OutOfTimeViewController: UIViewController, RootContainment {
 
         paymentState = .restoringPurchases
 
-        _ = interactor.restorePurchases(for: accountData.number) { [weak self] completion in
+        _ = interactor.restorePurchases(for: accountData.number) { [weak self] result in
             guard let self = self else { return }
 
-            switch completion {
+            switch result {
             case let .success(response):
                 self.showAlertIfNoTimeAdded(with: response, context: .restoration)
 
-            case let .failure(error):
+            case let .failure(error as StorePaymentManagerError):
                 self.showRestorePurchasesErrorAlert(error: error)
 
-            case .cancelled:
+            default:
                 break
             }
 
diff --git a/ios/MullvadVPN/ProblemReportInteractor.swift b/ios/MullvadVPN/ProblemReportInteractor.swift
index 744eedcbac..bac2c375a4 100644
--- a/ios/MullvadVPN/ProblemReportInteractor.swift
+++ b/ios/MullvadVPN/ProblemReportInteractor.swift
@@ -40,7 +40,7 @@ final class ProblemReportInteractor {
     func sendReport(
         email: String,
         message: String,
-        completion: @escaping (OperationCompletion<Void, REST.Error>) -> Void
+        completion: @escaping (Result<Void, Error>) -> Void
     ) -> Cancellable {
         let request = REST.ProblemReportRequest(
             address: email,
diff --git a/ios/MullvadVPN/ProblemReportSubmissionOverlayView.swift b/ios/MullvadVPN/ProblemReportSubmissionOverlayView.swift
index 160128dce9..0b5a8b5bf5 100644
--- a/ios/MullvadVPN/ProblemReportSubmissionOverlayView.swift
+++ b/ios/MullvadVPN/ProblemReportSubmissionOverlayView.swift
@@ -17,7 +17,7 @@ class ProblemReportSubmissionOverlayView: UIView {
     enum State {
         case sending
         case sent(_ email: String)
-        case failure(REST.Error)
+        case failure(Error)
 
         var title: String? {
             switch self {
@@ -96,7 +96,11 @@ class ProblemReportSubmissionOverlayView: UIView {
                 return combinedAttributedString
 
             case let .failure(error):
-                return error.displayErrorDescription.flatMap { NSAttributedString(string: $0) }
+                if let error = error as? REST.Error {
+                    return error.displayErrorDescription.flatMap { NSAttributedString(string: $0) }
+                } else {
+                    return NSAttributedString(string: error.localizedDescription)
+                }
             }
         }
     }
diff --git a/ios/MullvadVPN/ProblemReportViewController.swift b/ios/MullvadVPN/ProblemReportViewController.swift
index c894664679..4a1bd4596b 100644
--- a/ios/MullvadVPN/ProblemReportViewController.swift
+++ b/ios/MullvadVPN/ProblemReportViewController.swift
@@ -654,7 +654,7 @@ final class ProblemReportViewController: UIViewController, UITextFieldDelegate {
 
     private func didSendProblemReport(
         viewModel: ViewModel,
-        completion: OperationCompletion<Void, REST.Error>
+        completion: Result<Void, Error>
     ) {
         switch completion {
         case .success:
@@ -665,9 +665,6 @@ final class ProblemReportViewController: UIViewController, UITextFieldDelegate {
 
         case let .failure(error):
             submissionOverlayView.state = .failure(error)
-
-        case .cancelled:
-            submissionOverlayView.state = .failure(.network(URLError(.cancelled)))
         }
 
         navigationItem.setHidesBackButton(false, animated: true)
diff --git a/ios/MullvadVPN/RelayCacheTracker/RelayCacheTracker.swift b/ios/MullvadVPN/RelayCacheTracker/RelayCacheTracker.swift
index dedfa1825d..75b73b2119 100644
--- a/ios/MullvadVPN/RelayCacheTracker/RelayCacheTracker.swift
+++ b/ios/MullvadVPN/RelayCacheTracker/RelayCacheTracker.swift
@@ -94,28 +94,22 @@ final class RelayCacheTracker {
         timerSource = nil
     }
 
-    func updateRelays(
-        completionHandler: (
-            (OperationCompletion<RelaysFetchResult, Error>) -> Void
-        )? = nil
-    ) -> Cancellable {
-        let operation = ResultBlockOperation<RelaysFetchResult, Error>(
-            dispatchQueue: nil
-        ) { operation in
+    func updateRelays(completionHandler: ((Result<RelaysFetchResult, Error>) -> Void)? = nil)
+        -> Cancellable
+    {
+        let operation = ResultBlockOperation<RelaysFetchResult>(dispatchQueue: nil) { operation in
             let cachedRelays = try? self.getCachedRelays()
 
             if self.getNextUpdateDate() > Date() {
-                operation.finish(completion: .success(.throttled))
+                operation.finish(result: .success(.throttled))
                 return
             }
 
             let task = self.apiProxy.getRelays(
                 etag: cachedRelays?.etag,
                 retryStrategy: .noRetry
-            ) { completion in
-                operation.finish(
-                    completion: self.handleResponse(completion: completion)
-                )
+            ) { result in
+                operation.finish(result: self.handleResponse(result: result))
             }
 
             operation.addCancellationBlock {
@@ -181,10 +175,10 @@ final class RelayCacheTracker {
         return max(nextUpdate, Date())
     }
 
-    private func handleResponse(
-        completion: OperationCompletion<REST.ServerRelaysCacheResponse, REST.Error>
-    ) -> OperationCompletion<RelaysFetchResult, Error> {
-        let mappedCompletion = completion.tryMap { response -> RelaysFetchResult in
+    private func handleResponse(result: Result<REST.ServerRelaysCacheResponse, Error>)
+        -> Result<RelaysFetchResult, Error>
+    {
+        return result.tryMap { response -> RelaysFetchResult in
             switch response {
             case let .newContent(etag, relays):
                 try self.storeResponse(etag: etag, relays: relays)
@@ -194,16 +188,14 @@ final class RelayCacheTracker {
             case .notModified:
                 return .sameContent
             }
-        }
+        }.inspectError { error in
+            guard !error.isOperationCancellationError else { return }
 
-        if let error = mappedCompletion.error {
             logger.error(
                 error: error,
                 message: "Failed to update relays."
             )
         }
-
-        return mappedCompletion
     }
 
     private func storeResponse(etag: String?, relays: REST.ServerRelaysResponse) throws {
diff --git a/ios/MullvadVPN/Result+Extensions.swift b/ios/MullvadVPN/Result+Extensions.swift
index 0ea447752e..204df0714e 100644
--- a/ios/MullvadVPN/Result+Extensions.swift
+++ b/ios/MullvadVPN/Result+Extensions.swift
@@ -26,6 +26,30 @@ extension Result {
             return error
         }
     }
+
+    var isSuccess: Bool {
+        switch self {
+        case .success:
+            return true
+        case .failure:
+            return false
+        }
+    }
+
+    func tryMap<NewSuccess>(_ body: (Success) throws -> NewSuccess) -> Result<NewSuccess, Error> {
+        return Result<NewSuccess, Error> {
+            let value = try self.get()
+
+            return try body(value)
+        }
+    }
+
+    @discardableResult func inspectError(_ body: (Failure) -> Void) -> Self {
+        if case let .failure(error) = self {
+            body(error)
+        }
+        return self
+    }
 }
 
 extension Result {
diff --git a/ios/MullvadVPN/SceneDelegate.swift b/ios/MullvadVPN/SceneDelegate.swift
index ac680b9906..92e3867dcd 100644
--- a/ios/MullvadVPN/SceneDelegate.swift
+++ b/ios/MullvadVPN/SceneDelegate.swift
@@ -629,16 +629,16 @@ class SceneDelegate: UIResponder, UIWindowSceneDelegate, UISplitViewControllerDe
     func loginViewController(
         _ controller: LoginViewController,
         shouldHandleLoginAction action: LoginAction,
-        completion: @escaping (OperationCompletion<StoredAccountData?, Error>) -> Void
+        completion: @escaping (Result<StoredAccountData?, Error>) -> Void
     ) {
         setEnableSettingsButton(isEnabled: false, from: controller)
 
-        tunnelManager.setAccount(action: action.setAccountAction) { operationCompletion in
-            switch operationCompletion {
+        tunnelManager.setAccount(action: action.setAccountAction) { result in
+            switch result {
             case .success:
                 // RootContainer's settings button will be re-enabled in
                 // `loginViewControllerDidFinishLogin`
-                completion(operationCompletion)
+                completion(result)
 
             case let .failure(error):
                 // Show device management controller when too many devices detected during log in.
@@ -664,7 +664,7 @@ class SceneDelegate: UIResponder, UIWindowSceneDelegate, UISplitViewControllerDe
                             )
 
                             // Return .cancelled to login controller upon success.
-                            completion(operationCompletion.flatMap { .cancelled })
+                            completion(result.flatMap { _ in .failure(OperationError.cancelled) })
 
                             self?.setEnableSettingsButton(isEnabled: true, from: controller)
                         }
@@ -672,9 +672,9 @@ class SceneDelegate: UIResponder, UIWindowSceneDelegate, UISplitViewControllerDe
                     fallthrough
                 }
 
-            case .cancelled:
+            case .failure(OperationError.cancelled):
                 self.setEnableSettingsButton(isEnabled: true, from: controller)
-                completion(operationCompletion)
+                completion(result)
             }
         }
     }
diff --git a/ios/MullvadVPN/SettingsManager/Migrations/MigrationFromV1ToV2.swift b/ios/MullvadVPN/SettingsManager/Migrations/MigrationFromV1ToV2.swift
index cea71d5924..a7f8883c0f 100644
--- a/ios/MullvadVPN/SettingsManager/Migrations/MigrationFromV1ToV2.swift
+++ b/ios/MullvadVPN/SettingsManager/Migrations/MigrationFromV1ToV2.swift
@@ -19,8 +19,10 @@ final class MigrationFromV1ToV2: Migration {
     private var accountTask: Cancellable?
     private var deviceTask: Cancellable?
 
-    private var accountCompletion: OperationCompletion<REST.AccountData, REST.Error> = .cancelled
-    private var devicesCompletion: OperationCompletion<[REST.Device], REST.Error> = .cancelled
+    private var accountCompletion: Result<REST.AccountData, Error> = .failure(
+        OperationError.cancelled
+    )
+    private var devicesCompletion: Result<[REST.Device], Error> = .failure(OperationError.cancelled)
 
     private let legacySettings: LegacyTunnelSettings
 
diff --git a/ios/MullvadVPN/StorePaymentManager/SendStoreReceiptOperation.swift b/ios/MullvadVPN/StorePaymentManager/SendStoreReceiptOperation.swift
index 73e9788c2b..4afb212585 100644
--- a/ios/MullvadVPN/StorePaymentManager/SendStoreReceiptOperation.swift
+++ b/ios/MullvadVPN/StorePaymentManager/SendStoreReceiptOperation.swift
@@ -13,10 +13,8 @@ import MullvadTypes
 import Operations
 import StoreKit
 
-class SendStoreReceiptOperation: ResultOperation<
-    REST.CreateApplePaymentResponse,
-    StorePaymentManagerError
->, SKRequestDelegate {
+class SendStoreReceiptOperation: ResultOperation<REST.CreateApplePaymentResponse>, SKRequestDelegate
+{
     private let apiProxy: REST.APIProxy
     private let accountNumber: String
 
@@ -75,7 +73,7 @@ class SendStoreReceiptOperation: ResultOperation<
                 error: error,
                 message: "Failed to read the AppStore receipt."
             )
-            finish(completion: .failure(.readReceipt(error)))
+            finish(result: .failure(StorePaymentManagerError.readReceipt(error)))
         }
     }
 
@@ -92,7 +90,7 @@ class SendStoreReceiptOperation: ResultOperation<
                     error: error,
                     message: "Failed to read the AppStore receipt after refresh."
                 )
-                self.finish(completion: .failure(.readReceipt(error)))
+                self.finish(result: .failure(StorePaymentManagerError.readReceipt(error)))
             }
         }
     }
@@ -103,7 +101,7 @@ class SendStoreReceiptOperation: ResultOperation<
                 error: error,
                 message: "Failed to refresh the AppStore receipt."
             )
-            self.finish(completion: .failure(.readReceipt(error)))
+            self.finish(result: .failure(StorePaymentManagerError.readReceipt(error)))
         }
     }
 
@@ -138,8 +136,8 @@ class SendStoreReceiptOperation: ResultOperation<
             accountNumber: accountNumber,
             receiptString: receiptData,
             retryStrategy: .noRetry
-        ) { completion in
-            switch completion {
+        ) { result in
+            switch result {
             case let .success(response):
                 self.logger.info(
                     """
@@ -148,18 +146,19 @@ class SendStoreReceiptOperation: ResultOperation<
                     New expiry: \(response.newExpiry.logFormatDate())
                     """
                 )
-                self.finish(completion: .success(response))
+                self.finish(result: .success(response))
 
             case let .failure(error):
-                self.logger.error(
-                    error: error,
-                    message: "Failed to send the AppStore receipt."
-                )
-                self.finish(completion: .failure(.sendReceipt(error)))
-
-            case .cancelled:
-                self.logger.debug("Receipt submission cancelled.")
-                self.finish(completion: .cancelled)
+                if error.isOperationCancellationError {
+                    self.logger.debug("Receipt submission cancelled.")
+                    self.finish(result: .failure(error))
+                } else {
+                    self.logger.error(
+                        error: error,
+                        message: "Failed to send the AppStore receipt."
+                    )
+                    self.finish(result: .failure(StorePaymentManagerError.sendReceipt(error)))
+                }
             }
         }
     }
diff --git a/ios/MullvadVPN/StorePaymentManager/StorePaymentManager.swift b/ios/MullvadVPN/StorePaymentManager/StorePaymentManager.swift
index 5aa5db8316..40e1b6b7e3 100644
--- a/ios/MullvadVPN/StorePaymentManager/StorePaymentManager.swift
+++ b/ios/MullvadVPN/StorePaymentManager/StorePaymentManager.swift
@@ -110,7 +110,7 @@ final class StorePaymentManager: NSObject, SKPaymentTransactionObserver {
 
     func requestProducts(
         with productIdentifiers: Set<StoreSubscription>,
-        completionHandler: @escaping (OperationCompletion<SKProductsResponse, Error>) -> Void
+        completionHandler: @escaping (Result<SKProductsResponse, Error>) -> Void
     ) -> Cancellable {
         let productIdentifiers = productIdentifiers.productIdentifiersSet
         let operation = ProductsRequestOperation(
@@ -149,10 +149,7 @@ final class StorePaymentManager: NSObject, SKPaymentTransactionObserver {
 
     func restorePurchases(
         for accountNumber: String,
-        completionHandler: @escaping (OperationCompletion<
-            REST.CreateApplePaymentResponse,
-            StorePaymentManagerError
-        >) -> Void
+        completionHandler: @escaping (Result<REST.CreateApplePaymentResponse, Error>) -> Void
     ) -> Cancellable {
         return sendStoreReceipt(
             accountNumber: accountNumber,
@@ -184,15 +181,12 @@ final class StorePaymentManager: NSObject, SKPaymentTransactionObserver {
         accountNumber: String,
         completionHandler: @escaping (StorePaymentManagerError?) -> Void
     ) {
-        let accountOperation = ResultBlockOperation<
-            REST.AccountData,
-            REST.Error
-        >(dispatchQueue: .main) { op in
+        let accountOperation = ResultBlockOperation<REST.AccountData>(dispatchQueue: .main) { op in
             let task = self.accountsProxy.getAccountData(
                 accountNumber: accountNumber,
                 retryStrategy: .default
-            ) { completion in
-                op.finish(completion: completion)
+            ) { result in
+                op.finish(result: result)
             }
 
             op.addCancellationBlock {
@@ -207,16 +201,8 @@ final class StorePaymentManager: NSObject, SKPaymentTransactionObserver {
         ))
 
         accountOperation.completionQueue = .main
-        accountOperation.completionHandler = { completion in
-            var error: REST.Error?
-
-            if case .cancelled = completion {
-                error = .network(URLError(.cancelled))
-            } else {
-                error = completion.error
-            }
-
-            completionHandler(error.map { .validateAccount($0) })
+        accountOperation.completionHandler = { result in
+            completionHandler(result.error.map { StorePaymentManagerError.validateAccount($0) })
         }
 
         operationQueue.addOperation(accountOperation)
@@ -225,10 +211,7 @@ final class StorePaymentManager: NSObject, SKPaymentTransactionObserver {
     private func sendStoreReceipt(
         accountNumber: String,
         forceRefresh: Bool,
-        completionHandler: @escaping (OperationCompletion<
-            REST.CreateApplePaymentResponse,
-            StorePaymentManagerError
-        >) -> Void
+        completionHandler: @escaping (Result<REST.CreateApplePaymentResponse, Error>) -> Void
     ) -> Cancellable {
         let operation = SendStoreReceiptOperation(
             apiProxy: apiProxy,
@@ -333,10 +316,10 @@ final class StorePaymentManager: NSObject, SKPaymentTransactionObserver {
             return
         }
 
-        _ = sendStoreReceipt(accountNumber: accountNumber, forceRefresh: false) { completion in
+        _ = sendStoreReceipt(accountNumber: accountNumber, forceRefresh: false) { result in
             var event: StorePaymentEvent?
 
-            switch completion {
+            switch result {
             case let .success(response):
                 self.paymentQueue.finishTransaction(transaction)
 
@@ -346,7 +329,7 @@ final class StorePaymentManager: NSObject, SKPaymentTransactionObserver {
                     serverResponse: response
                 ))
 
-            case let .failure(error):
+            case let .failure(error as StorePaymentManagerError):
                 event = StorePaymentEvent.failure(StorePaymentFailure(
                     transaction: transaction,
                     payment: transaction.payment,
@@ -354,7 +337,7 @@ final class StorePaymentManager: NSObject, SKPaymentTransactionObserver {
                     error: error
                 ))
 
-            case .cancelled:
+            default:
                 break
             }
 
diff --git a/ios/MullvadVPN/StorePaymentManager/StorePaymentManagerError.swift b/ios/MullvadVPN/StorePaymentManager/StorePaymentManagerError.swift
index 660d181df4..f7df5e4489 100644
--- a/ios/MullvadVPN/StorePaymentManager/StorePaymentManagerError.swift
+++ b/ios/MullvadVPN/StorePaymentManager/StorePaymentManagerError.swift
@@ -16,7 +16,7 @@ enum StorePaymentManagerError: LocalizedError, WrappingError {
     case noAccountSet
 
     /// Failure to validate the account token.
-    case validateAccount(REST.Error)
+    case validateAccount(Error)
 
     /// Failure to handle payment transaction. Contains error returned by StoreKit.
     case storePayment(Error)
@@ -25,7 +25,7 @@ enum StorePaymentManagerError: LocalizedError, WrappingError {
     case readReceipt(Error)
 
     /// Failure to send the AppStore receipt to backend.
-    case sendReceipt(REST.Error)
+    case sendReceipt(Error)
 
     var errorDescription: String? {
         switch self {
diff --git a/ios/MullvadVPN/StorePaymentManagerError+Display.swift b/ios/MullvadVPN/StorePaymentManagerError+Display.swift
index 3015c69081..a2adb551ad 100644
--- a/ios/MullvadVPN/StorePaymentManagerError+Display.swift
+++ b/ios/MullvadVPN/StorePaymentManagerError+Display.swift
@@ -21,8 +21,8 @@ extension StorePaymentManagerError: DisplayError {
                 comment: ""
             )
 
-        case let .validateAccount(restError):
-            let reason = restError.displayErrorDescription ?? ""
+        case let .validateAccount(error):
+            let reason = (error as? DisplayError)?.displayErrorDescription ?? ""
 
             return String(
                 format: NSLocalizedString(
@@ -60,8 +60,8 @@ extension StorePaymentManagerError: DisplayError {
                 )
             }
 
-        case let .sendReceipt(restError):
-            let reason = restError.displayErrorDescription ?? ""
+        case let .sendReceipt(error):
+            let reason = (error as? DisplayError)?.displayErrorDescription ?? ""
             let errorFormat = NSLocalizedString(
                 "SEND_RECEIPT_ERROR",
                 tableName: "StorePaymentManager",
diff --git a/ios/MullvadVPN/TransportMonitor/PacketTunnelTransport.swift b/ios/MullvadVPN/TransportMonitor/PacketTunnelTransport.swift
index aa85eda6b2..4ee628751d 100644
--- a/ios/MullvadVPN/TransportMonitor/PacketTunnelTransport.swift
+++ b/ios/MullvadVPN/TransportMonitor/PacketTunnelTransport.swift
@@ -9,6 +9,7 @@
 import Foundation
 import protocol MullvadREST.RESTTransport
 import MullvadTypes
+import Operations
 import TunnelProviderMessaging
 
 struct PacketTunnelTransport: RESTTransport {
@@ -30,9 +31,6 @@ struct PacketTunnelTransport: RESTTransport {
 
         return tunnel.sendRequest(proxyRequest) { result in
             switch result {
-            case .cancelled:
-                completion(nil, nil, URLError(.cancelled))
-
             case let .success(reply):
                 completion(
                     reply.data,
@@ -41,7 +39,9 @@ struct PacketTunnelTransport: RESTTransport {
                 )
 
             case let .failure(error):
-                completion(nil, nil, error)
+                let returnError = error.isOperationCancellationError ? URLError(.cancelled) : error
+
+                completion(nil, nil, returnError)
             }
         }
     }
diff --git a/ios/MullvadVPN/TunnelManager/LoadTunnelConfigurationOperation.swift b/ios/MullvadVPN/TunnelManager/LoadTunnelConfigurationOperation.swift
index 4f5bfa60b8..20b5564e6f 100644
--- a/ios/MullvadVPN/TunnelManager/LoadTunnelConfigurationOperation.swift
+++ b/ios/MullvadVPN/TunnelManager/LoadTunnelConfigurationOperation.swift
@@ -11,7 +11,7 @@ import MullvadLogging
 import MullvadTypes
 import Operations
 
-class LoadTunnelConfigurationOperation: ResultOperation<Void, Error> {
+class LoadTunnelConfigurationOperation: ResultOperation<Void> {
     private let logger = Logger(label: "LoadTunnelConfigurationOperation")
     private let interactor: TunnelInteractor
 
@@ -54,7 +54,7 @@ class LoadTunnelConfigurationOperation: ResultOperation<Void, Error> {
         interactor.setTunnel(tunnel, shouldRefreshTunnelState: true)
         interactor.setConfigurationLoaded()
 
-        finish(completion: .success(()))
+        finish(result: .success(()))
     }
 
     private func readSettings() -> Result<TunnelSettingsV2?, Error> {
diff --git a/ios/MullvadVPN/TunnelManager/ReconnectTunnelOperation.swift b/ios/MullvadVPN/TunnelManager/ReconnectTunnelOperation.swift
index 42ed31c941..bbaa83850e 100644
--- a/ios/MullvadVPN/TunnelManager/ReconnectTunnelOperation.swift
+++ b/ios/MullvadVPN/TunnelManager/ReconnectTunnelOperation.swift
@@ -13,7 +13,7 @@ import Operations
 import RelayCache
 import RelaySelector
 
-class ReconnectTunnelOperation: ResultOperation<Void, Error> {
+class ReconnectTunnelOperation: ResultOperation<Void> {
     private let interactor: TunnelInteractor
     private let selectNewRelay: Bool
     private var task: Cancellable?
@@ -31,20 +31,19 @@ class ReconnectTunnelOperation: ResultOperation<Void, Error> {
 
     override func main() {
         guard let tunnel = interactor.tunnel else {
-            finish(completion: .failure(UnsetTunnelError()))
+            finish(result: .failure(UnsetTunnelError()))
             return
         }
 
         do {
             let selectorResult = selectNewRelay ? try interactor.selectRelay() : nil
 
-            task = tunnel.reconnectTunnel(
-                relaySelectorResult: selectorResult
-            ) { [weak self] completion in
-                self?.finish(completion: completion)
-            }
+            task = tunnel
+                .reconnectTunnel(relaySelectorResult: selectorResult) { [weak self] result in
+                    self?.finish(result: result)
+                }
         } catch {
-            finish(completion: .failure(error))
+            finish(result: .failure(error))
         }
     }
 
diff --git a/ios/MullvadVPN/TunnelManager/RotateKeyOperation.swift b/ios/MullvadVPN/TunnelManager/RotateKeyOperation.swift
index 88a4f99b5e..5f74e5ee2a 100644
--- a/ios/MullvadVPN/TunnelManager/RotateKeyOperation.swift
+++ b/ios/MullvadVPN/TunnelManager/RotateKeyOperation.swift
@@ -13,7 +13,7 @@ import MullvadTypes
 import Operations
 import class WireGuardKitTypes.PrivateKey
 
-class RotateKeyOperation: ResultOperation<Bool, Error> {
+class RotateKeyOperation: ResultOperation<Bool> {
     private let interactor: TunnelInteractor
 
     private let devicesProxy: REST.DevicesProxy
@@ -41,7 +41,7 @@ class RotateKeyOperation: ResultOperation<Bool, Error> {
 
     override func main() {
         guard case let .loggedIn(accountData, deviceData) = interactor.deviceState else {
-            finish(completion: .failure(InvalidDeviceStateError()))
+            finish(result: .failure(InvalidDeviceStateError()))
             return
         }
 
@@ -52,7 +52,7 @@ class RotateKeyOperation: ResultOperation<Bool, Error> {
             if nextRotationDate > Date() {
                 logger.debug("Throttle private key rotation.")
 
-                finish(completion: .success(false))
+                finish(result: .success(false))
                 return
             } else {
                 logger.debug("Private key is old enough, rotate right away.")
@@ -70,11 +70,11 @@ class RotateKeyOperation: ResultOperation<Bool, Error> {
             identifier: deviceData.identifier,
             publicKey: newPrivateKey.publicKey,
             retryStrategy: .default
-        ) { completion in
+        ) { result in
             self.dispatchQueue.async {
                 self.didRotateKey(
                     newPrivateKey: newPrivateKey,
-                    completion: completion
+                    result: result
                 )
             }
         }
@@ -85,11 +85,8 @@ class RotateKeyOperation: ResultOperation<Bool, Error> {
         task = nil
     }
 
-    private func didRotateKey(
-        newPrivateKey: PrivateKey,
-        completion: OperationCompletion<REST.Device, REST.Error>
-    ) {
-        switch completion {
+    private func didRotateKey(newPrivateKey: PrivateKey, result: Result<REST.Device, Error>) {
+        switch result {
         case let .success(device):
             logger.debug("Successfully rotated device key. Persisting settings...")
 
@@ -103,20 +100,19 @@ class RotateKeyOperation: ResultOperation<Bool, Error> {
 
                 interactor.setDeviceState(.loggedIn(accountData, deviceData), persist: true)
 
-                finish(completion: .success(true))
+                finish(result: .success(true))
             default:
-                finish(completion: .failure(InvalidDeviceStateError()))
+                finish(result: .failure(InvalidDeviceStateError()))
             }
 
         case let .failure(error):
-            logger.error(
-                error: error,
-                message: "Failed to rotate device key."
-            )
-            finish(completion: .failure(error))
-
-        case .cancelled:
-            finish(completion: .cancelled)
+            if !error.isOperationCancellationError {
+                logger.error(
+                    error: error,
+                    message: "Failed to rotate device key."
+                )
+            }
+            finish(result: .failure(error))
         }
     }
 }
diff --git a/ios/MullvadVPN/TunnelManager/SendTunnelProviderMessageOperation.swift b/ios/MullvadVPN/TunnelManager/SendTunnelProviderMessageOperation.swift
index 9fc30565f5..b7fafa326d 100644
--- a/ios/MullvadVPN/TunnelManager/SendTunnelProviderMessageOperation.swift
+++ b/ios/MullvadVPN/TunnelManager/SendTunnelProviderMessageOperation.swift
@@ -20,7 +20,7 @@ private let connectingStateWaitDelay: TimeInterval = 5
 /// Default timeout in seconds.
 private let defaultTimeout: TimeInterval = 5
 
-final class SendTunnelProviderMessageOperation<Output>: ResultOperation<Output, Error> {
+final class SendTunnelProviderMessageOperation<Output>: ResultOperation<Output> {
     typealias DecoderHandler = (Data?) throws -> Output
 
     private let tunnel: Tunnel
@@ -68,11 +68,11 @@ final class SendTunnelProviderMessageOperation<Output>: ResultOperation<Output,
 
     override func operationDidCancel() {
         if isExecuting {
-            finish(completion: .cancelled)
+            finish(result: .failure(OperationError.cancelled))
         }
     }
 
-    override func finish(completion: Completion) {
+    override func finish(result: Result<Output, Error>) {
         // Release status observer.
         removeVPNStatusObserver()
 
@@ -81,7 +81,7 @@ final class SendTunnelProviderMessageOperation<Output>: ResultOperation<Output,
         waitForConnectingStateWork?.cancel()
 
         // Finish operation.
-        super.finish(completion: completion)
+        super.finish(result: result)
     }
 
     private func removeVPNStatusObserver() {
@@ -91,7 +91,7 @@ final class SendTunnelProviderMessageOperation<Output>: ResultOperation<Output,
 
     private func setTimeoutTimer(connectingStateWaitDelay delay: TimeInterval) {
         let workItem = DispatchWorkItem { [weak self] in
-            self?.finish(completion: .failure(SendTunnelProviderMessageError.timeout))
+            self?.finish(result: .failure(SendTunnelProviderMessageError.timeout))
         }
 
         // Cancel pending timeout work.
@@ -124,7 +124,7 @@ final class SendTunnelProviderMessageOperation<Output>: ResultOperation<Output,
             sendMessage()
 
         case .invalid, .disconnecting, .disconnected:
-            finish(completion: .failure(SendTunnelProviderMessageError.tunnelDown(status)))
+            finish(result: .failure(SendTunnelProviderMessageError.tunnelDown(status)))
 
         @unknown default:
             break
@@ -180,7 +180,7 @@ final class SendTunnelProviderMessageOperation<Output>: ResultOperation<Output,
         do {
             messageData = try message.encode()
         } catch {
-            finish(completion: .failure(error))
+            finish(result: .failure(error))
             return
         }
 
@@ -192,11 +192,11 @@ final class SendTunnelProviderMessageOperation<Output>: ResultOperation<Output,
                 self.dispatchQueue.async {
                     let decodingResult = Result { try self.decoderHandler(responseData) }
 
-                    self.finish(completion: OperationCompletion(result: decodingResult))
+                    self.finish(result: decodingResult)
                 }
             }
         } catch {
-            finish(completion: .failure(SendTunnelProviderMessageError.system(error)))
+            finish(result: .failure(SendTunnelProviderMessageError.system(error)))
         }
     }
 }
diff --git a/ios/MullvadVPN/TunnelManager/SetAccountOperation.swift b/ios/MullvadVPN/TunnelManager/SetAccountOperation.swift
index e2c1de0656..d07170bdc2 100644
--- a/ios/MullvadVPN/TunnelManager/SetAccountOperation.swift
+++ b/ios/MullvadVPN/TunnelManager/SetAccountOperation.swift
@@ -62,7 +62,7 @@ private struct SetAccountContext: OperationInputContext {
     }
 }
 
-class SetAccountOperation: ResultOperation<StoredAccountData?, Error> {
+class SetAccountOperation: ResultOperation<StoredAccountData?> {
     private let interactor: TunnelInteractor
     private let accountsProxy: REST.AccountsProxy
     private let devicesProxy: REST.DevicesProxy
@@ -156,7 +156,7 @@ class SetAccountOperation: ResultOperation<StoredAccountData?, Error> {
 
     private func completeOperation(accountData: StoredAccountData?) {
         guard !isCancelled else {
-            finish(completion: .cancelled)
+            finish(result: .failure(OperationError.cancelled))
             return
         }
 
@@ -165,13 +165,13 @@ class SetAccountOperation: ResultOperation<StoredAccountData?, Error> {
         }
 
         if let error = errors.first {
-            finish(completion: .failure(error))
+            finish(result: .failure(error))
         } else {
-            finish(completion: .success(accountData))
+            finish(result: .success(accountData))
         }
     }
 
-    private func getAccountDataOperation() -> ResultOperation<StoredAccountData, Error>? {
+    private func getAccountDataOperation() -> ResultOperation<StoredAccountData>? {
         switch action {
         case .new:
             return getCreateAccountOperation()
@@ -184,19 +184,20 @@ class SetAccountOperation: ResultOperation<StoredAccountData?, Error> {
         }
     }
 
-    private func getCreateAccountOperation() -> ResultBlockOperation<StoredAccountData, Error> {
-        let operation = ResultBlockOperation<StoredAccountData, Error>(dispatchQueue: dispatchQueue)
+    private func getCreateAccountOperation() -> ResultBlockOperation<StoredAccountData> {
+        let operation = ResultBlockOperation<StoredAccountData>(dispatchQueue: dispatchQueue)
 
         operation.setExecutionBlock { operation in
             self.logger.debug("Create new account...")
 
-            let task = self.accountsProxy.createAccount(retryStrategy: .default) { completion in
-                let mappedCompletion = completion.mapError { error -> Error in
+            let task = self.accountsProxy.createAccount(retryStrategy: .default) { result in
+                let result = result.inspectError { error in
+                    guard !error.isOperationCancellationError else { return }
+
                     self.logger.error(
                         error: error,
                         message: "Failed to create new account."
                     )
-                    return error
                 }.map { newAccountData -> StoredAccountData in
                     self.logger.debug("Created new account.")
 
@@ -207,7 +208,7 @@ class SetAccountOperation: ResultOperation<StoredAccountData?, Error> {
                     )
                 }
 
-                operation.finish(completion: mappedCompletion)
+                operation.finish(result: result)
             }
 
             operation.addCancellationBlock {
@@ -219,9 +220,9 @@ class SetAccountOperation: ResultOperation<StoredAccountData?, Error> {
     }
 
     private func getExistingAccountOperation(accountNumber: String)
-        -> ResultOperation<StoredAccountData, Error>
+        -> ResultOperation<StoredAccountData>
     {
-        let operation = ResultBlockOperation<StoredAccountData, Error>(dispatchQueue: dispatchQueue)
+        let operation = ResultBlockOperation<StoredAccountData>(dispatchQueue: dispatchQueue)
 
         operation.setExecutionBlock { operation in
             self.logger.debug("Request account data...")
@@ -229,13 +230,14 @@ class SetAccountOperation: ResultOperation<StoredAccountData?, Error> {
             let task = self.accountsProxy.getAccountData(
                 accountNumber: accountNumber,
                 retryStrategy: .default
-            ) { completion in
-                let mappedCompletion = completion.mapError { error -> Error in
+            ) { result in
+                let result = result.inspectError { error in
+                    guard !error.isOperationCancellationError else { return }
+
                     self.logger.error(
                         error: error,
                         message: "Failed to receive account data."
                     )
-                    return error
                 }.map { accountData -> StoredAccountData in
                     self.logger.debug("Received account data.")
 
@@ -246,7 +248,7 @@ class SetAccountOperation: ResultOperation<StoredAccountData?, Error> {
                     )
                 }
 
-                operation.finish(completion: mappedCompletion)
+                operation.finish(result: result)
             }
 
             operation.addCancellationBlock {
@@ -257,12 +259,12 @@ class SetAccountOperation: ResultOperation<StoredAccountData?, Error> {
         return operation
     }
 
-    private func getDeleteDeviceOperation() -> ResultBlockOperation<Void, Error>? {
+    private func getDeleteDeviceOperation() -> AsyncBlockOperation? {
         guard case let .loggedIn(accountData, deviceData) = interactor.deviceState else {
             return nil
         }
 
-        let operation = ResultBlockOperation<Void, Error>(dispatchQueue: dispatchQueue)
+        let operation = AsyncBlockOperation(dispatchQueue: dispatchQueue)
 
         operation.setExecutionBlock { operation in
             self.logger.debug("Delete current device...")
@@ -271,23 +273,22 @@ class SetAccountOperation: ResultOperation<StoredAccountData?, Error> {
                 accountNumber: accountData.number,
                 identifier: deviceData.identifier,
                 retryStrategy: .default
-            ) { completion in
-                let mappedCompletion = completion
-                    .mapError { error -> Error in
-                        self.logger.error(
-                            error: error,
-                            message: "Failed to delete device."
-                        )
-                        return error
-                    }.map { isDeleted in
-                        if isDeleted {
-                            self.logger.debug("Deleted device.")
-                        } else {
-                            self.logger.debug("Device is already deleted.")
-                        }
-                    }
+            ) { result in
+                switch result {
+                case let .success(isDeleted):
+                    self.logger.debug(isDeleted ? "Deleted device." : "Device is already deleted.")
+
+                case let .failure(error) where !error.isOperationCancellationError:
+                    self.logger.error(
+                        error: error,
+                        message: "Failed to delete device."
+                    )
+
+                default:
+                    break
+                }
 
-                operation.finish(completion: mappedCompletion)
+                operation.finish(error: result.error)
             }
 
             operation.addCancellationBlock {
@@ -336,12 +337,11 @@ class SetAccountOperation: ResultOperation<StoredAccountData?, Error> {
     }
 
     private func getCreateDeviceOperation()
-        -> TransformOperation<StoredAccountData, (PrivateKey, REST.Device), Error>
+        -> TransformOperation<StoredAccountData, (PrivateKey, REST.Device)>
     {
         let createDeviceOperation = TransformOperation<
             StoredAccountData,
-            (PrivateKey, REST.Device),
-            Error
+            (PrivateKey, REST.Device)
         >(dispatchQueue: dispatchQueue)
 
         createDeviceOperation.setExecutionBlock { storedAccountData, operation in
@@ -369,17 +369,16 @@ class SetAccountOperation: ResultOperation<StoredAccountData?, Error> {
                 accountNumber: storedAccountData.number,
                 request: request,
                 retryStrategy: .default
-            ) { completion in
-                let mappedCompletion = completion
+            ) { result in
+                let result = result
                     .map { device in
                         return (privateKey, device)
                     }
-                    .mapError { error -> Error in
+                    .inspectError { error in
                         self.logger.error(error: error, message: "Failed to create device.")
-                        return error
                     }
 
-                operation.finish(completion: mappedCompletion)
+                operation.finish(result: result)
             }
 
             operation.addCancellationBlock {
@@ -391,10 +390,11 @@ class SetAccountOperation: ResultOperation<StoredAccountData?, Error> {
     }
 
     private func getSaveSettingsOperation()
-        -> TransformOperation<SetAccountResult, StoredAccountData, Error>
+        -> TransformOperation<SetAccountResult, StoredAccountData>
     {
         let saveSettingsOperation = TransformOperation<
-            SetAccountResult, StoredAccountData, Error
+            SetAccountResult,
+            StoredAccountData
         >(dispatchQueue: dispatchQueue)
 
         saveSettingsOperation.setExecutionBlock { input in
diff --git a/ios/MullvadVPN/TunnelManager/StartTunnelOperation.swift b/ios/MullvadVPN/TunnelManager/StartTunnelOperation.swift
index 12934a4790..6954fd3c24 100644
--- a/ios/MullvadVPN/TunnelManager/StartTunnelOperation.swift
+++ b/ios/MullvadVPN/TunnelManager/StartTunnelOperation.swift
@@ -14,7 +14,7 @@ import RelayCache
 import RelaySelector
 import TunnelProviderMessaging
 
-class StartTunnelOperation: ResultOperation<Void, Error> {
+class StartTunnelOperation: ResultOperation<Void> {
     typealias EncodeErrorHandler = (Error) -> Void
 
     private let interactor: TunnelInteractor
@@ -36,7 +36,7 @@ class StartTunnelOperation: ResultOperation<Void, Error> {
 
     override func main() {
         guard case .loggedIn = interactor.deviceState else {
-            finish(completion: .failure(InvalidDeviceStateError()))
+            finish(result: .failure(InvalidDeviceStateError()))
             return
         }
 
@@ -47,21 +47,21 @@ class StartTunnelOperation: ResultOperation<Void, Error> {
                 tunnelStatus.state = .disconnecting(.reconnect)
             }
 
-            finish(completion: .success(()))
+            finish(result: .success(()))
 
         case .disconnected, .pendingReconnect:
             do {
                 let selectorResult = try interactor.selectRelay()
 
                 makeTunnelProviderAndStartTunnel(selectorResult: selectorResult) { error in
-                    self.finish(completion: OperationCompletion(error: error))
+                    self.finish(result: error.map { .failure($0) } ?? .success(()))
                 }
             } catch {
-                finish(completion: .failure(error))
+                finish(result: .failure(error))
             }
 
         default:
-            finish(completion: .success(()))
+            finish(result: .success(()))
         }
     }
 
diff --git a/ios/MullvadVPN/TunnelManager/StopTunnelOperation.swift b/ios/MullvadVPN/TunnelManager/StopTunnelOperation.swift
index 2c63b1ae2e..38e60c7cf4 100644
--- a/ios/MullvadVPN/TunnelManager/StopTunnelOperation.swift
+++ b/ios/MullvadVPN/TunnelManager/StopTunnelOperation.swift
@@ -9,7 +9,7 @@
 import Foundation
 import Operations
 
-class StopTunnelOperation: ResultOperation<Void, Error> {
+class StopTunnelOperation: ResultOperation<Void> {
     private let interactor: TunnelInteractor
 
     init(
@@ -33,11 +33,11 @@ class StopTunnelOperation: ResultOperation<Void, Error> {
                 tunnelStatus.state = .disconnecting(.nothing)
             }
 
-            finish(completion: .success(()))
+            finish(result: .success(()))
 
         case .connected, .connecting, .reconnecting, .waitingForConnectivity:
             guard let tunnel = interactor.tunnel else {
-                finish(completion: .failure(UnsetTunnelError()))
+                finish(result: .failure(UnsetTunnelError()))
                 return
             }
 
@@ -47,16 +47,16 @@ class StopTunnelOperation: ResultOperation<Void, Error> {
             tunnel.saveToPreferences { error in
                 self.dispatchQueue.async {
                     if let error = error {
-                        self.finish(completion: .failure(error))
+                        self.finish(result: .failure(error))
                     } else {
                         tunnel.stop()
-                        self.finish(completion: .success(()))
+                        self.finish(result: .success(()))
                     }
                 }
             }
 
         case .disconnected, .disconnecting, .pendingReconnect:
-            finish(completion: .success(()))
+            finish(result: .success(()))
         }
     }
 }
diff --git a/ios/MullvadVPN/TunnelManager/Tunnel+Messaging.swift b/ios/MullvadVPN/TunnelManager/Tunnel+Messaging.swift
index 339e9b0da6..7dea6451f6 100644
--- a/ios/MullvadVPN/TunnelManager/Tunnel+Messaging.swift
+++ b/ios/MullvadVPN/TunnelManager/Tunnel+Messaging.swift
@@ -27,7 +27,7 @@ extension Tunnel {
     /// Packet tunnel will reconnect to the current relay if relay selector result is not provided.
     func reconnectTunnel(
         relaySelectorResult: RelaySelectorResult?,
-        completionHandler: @escaping (OperationCompletion<Void, Error>) -> Void
+        completionHandler: @escaping (Result<Void, Error>) -> Void
     ) -> Cancellable {
         let operation = SendTunnelProviderMessageOperation(
             dispatchQueue: dispatchQueue,
@@ -43,7 +43,7 @@ extension Tunnel {
 
     /// Request status from packet tunnel process.
     func getTunnelStatus(
-        completionHandler: @escaping (OperationCompletion<PacketTunnelStatus, Error>) -> Void
+        completionHandler: @escaping (Result<PacketTunnelStatus, Error>) -> Void
     ) -> Cancellable {
         let operation = SendTunnelProviderMessageOperation(
             dispatchQueue: dispatchQueue,
@@ -60,7 +60,7 @@ extension Tunnel {
     /// Send HTTP request via packet tunnel process bypassing VPN.
     func sendRequest(
         _ proxyRequest: ProxyURLRequest,
-        completionHandler: @escaping (OperationCompletion<ProxyURLResponse, Error>) -> Void
+        completionHandler: @escaping (Result<ProxyURLResponse, Error>) -> Void
     ) -> Cancellable {
         let operation = SendTunnelProviderMessageOperation(
             dispatchQueue: dispatchQueue,
diff --git a/ios/MullvadVPN/TunnelManager/TunnelManager.swift b/ios/MullvadVPN/TunnelManager/TunnelManager.swift
index 3854f3ca54..6ac13e7ac3 100644
--- a/ios/MullvadVPN/TunnelManager/TunnelManager.swift
+++ b/ios/MullvadVPN/TunnelManager/TunnelManager.swift
@@ -67,7 +67,7 @@ final class TunnelManager: StorePaymentObserver {
     private var privateKeyRotationTimer: DispatchSourceTimer?
     private var lastKeyRotationData: (
         attempt: Date,
-        completion: OperationCompletion<Bool, Error>
+        completion: Result<Bool, Error>
     )?
     private var isRunningPeriodicPrivateKeyRotation = false
 
@@ -198,11 +198,11 @@ final class TunnelManager: StorePaymentObserver {
         logger.debug("Schedule next private key rotation at \(scheduleDate.logFormatDate()).")
     }
 
-    private func setFinishedKeyRotation(_ completion: OperationCompletion<Bool, Error>) {
+    private func setFinishedKeyRotation(_ result: Result<Bool, Error>) {
         nslock.lock()
         defer { nslock.unlock() }
 
-        lastKeyRotationData = (Date(), completion)
+        lastKeyRotationData = (Date(), result)
         updatePrivateKeyRotationTimer()
     }
 
@@ -252,15 +252,15 @@ final class TunnelManager: StorePaymentObserver {
         operationQueue.addOperation(loadTunnelOperation)
     }
 
-    func startTunnel(completionHandler: ((OperationCompletion<Void, Error>) -> Void)? = nil) {
+    func startTunnel(completionHandler: ((Error?) -> Void)? = nil) {
         let operation = StartTunnelOperation(
             dispatchQueue: internalQueue,
             interactor: TunnelInteractorProxy(self),
-            completionHandler: { [weak self] completion in
+            completionHandler: { [weak self] result in
                 guard let self = self else { return }
 
                 DispatchQueue.main.async {
-                    if let error = completion.error {
+                    if let error = result.error {
                         self.logger.error(
                             error: error,
                             message: "Failed to start the tunnel."
@@ -273,7 +273,7 @@ final class TunnelManager: StorePaymentObserver {
                         }
                     }
 
-                    completionHandler?(completion)
+                    completionHandler?(result.error)
                 }
             }
         )
@@ -288,15 +288,15 @@ final class TunnelManager: StorePaymentObserver {
         operationQueue.addOperation(operation)
     }
 
-    func stopTunnel(completionHandler: ((OperationCompletion<Void, Error>) -> Void)? = nil) {
+    func stopTunnel(completionHandler: ((Error?) -> Void)? = nil) {
         let operation = StopTunnelOperation(
             dispatchQueue: internalQueue,
             interactor: TunnelInteractorProxy(self)
-        ) { [weak self] completion in
+        ) { [weak self] result in
             guard let self = self else { return }
 
             DispatchQueue.main.async {
-                if let error = completion.error {
+                if let error = result.error {
                     self.logger.error(
                         error: error,
                         message: "Failed to stop the tunnel."
@@ -309,7 +309,7 @@ final class TunnelManager: StorePaymentObserver {
                     }
                 }
 
-                completionHandler?(completion)
+                completionHandler?(result.error)
             }
         }
 
@@ -325,7 +325,7 @@ final class TunnelManager: StorePaymentObserver {
 
     func reconnectTunnel(
         selectNewRelay: Bool,
-        completionHandler: ((OperationCompletion<Void, Error>) -> Void)? = nil
+        completionHandler: ((Error?) -> Void)? = nil
     ) {
         let operation = ReconnectTunnelOperation(
             dispatchQueue: internalQueue,
@@ -334,10 +334,10 @@ final class TunnelManager: StorePaymentObserver {
         )
 
         operation.completionQueue = .main
-        operation.completionHandler = { [weak self] completion in
-            self?.didReconnectTunnel(completion: completion)
+        operation.completionHandler = { [weak self] result in
+            self?.didReconnectTunnel(error: result.error)
 
-            completionHandler?(completion)
+            completionHandler?(result.error)
         }
 
         operation.addObserver(
@@ -356,7 +356,7 @@ final class TunnelManager: StorePaymentObserver {
 
     func setAccount(
         action: SetAccountAction,
-        completionHandler: @escaping (OperationCompletion<StoredAccountData?, Error>) -> Void
+        completionHandler: @escaping (Result<StoredAccountData?, Error>) -> Void
     ) {
         let operation = SetAccountOperation(
             dispatchQueue: internalQueue,
@@ -367,10 +367,10 @@ final class TunnelManager: StorePaymentObserver {
         )
 
         operation.completionQueue = .main
-        operation.completionHandler = { [weak self] completion in
+        operation.completionHandler = { [weak self] result in
             self?.resetKeyRotationData()
 
-            completionHandler(completion)
+            completionHandler(result)
         }
 
         operation.addObserver(BackgroundObserver(
@@ -461,7 +461,7 @@ final class TunnelManager: StorePaymentObserver {
 
     func rotatePrivateKey(
         forceRotate: Bool,
-        completionHandler: @escaping (OperationCompletion<Bool, Error>) -> Void
+        completionHandler: @escaping (Result<Bool, Error>) -> Void
     ) -> Cancellable {
         var rotationInterval: TimeInterval?
         if !forceRotate {
@@ -476,24 +476,23 @@ final class TunnelManager: StorePaymentObserver {
         )
 
         operation.completionQueue = .main
-        operation.completionHandler = { [weak self] completion in
+        operation.completionHandler = { [weak self] result in
             guard let self = self else { return }
 
-            self.setFinishedKeyRotation(completion)
+            self.setFinishedKeyRotation(result)
 
-            switch completion {
+            switch result {
             case .success:
                 self.reconnectTunnel(selectNewRelay: true) { _ in
-                    completionHandler(completion)
+                    completionHandler(result)
                 }
 
             case let .failure(error):
-                self.checkIfDeviceRevoked(error)
-
-                completionHandler(.failure(error))
+                if !error.isOperationCancellationError {
+                    self.checkIfDeviceRevoked(error)
+                }
 
-            case .cancelled:
-                completionHandler(completion)
+                completionHandler(result)
             }
         }
 
@@ -814,15 +813,12 @@ final class TunnelManager: StorePaymentObserver {
         )
     }
 
-    private func didReconnectTunnel(completion: OperationCompletion<Void, Error>) {
+    private func didReconnectTunnel(error: Error?) {
         nslock.lock()
         defer { nslock.unlock() }
 
-        if let error = completion.error {
-            logger.error(
-                error: error,
-                message: "Failed to reconnect the tunnel."
-            )
+        if let error = error, !error.isOperationCancellationError {
+            logger.error(error: error, message: "Failed to reconnect the tunnel.")
         }
 
         // Refresh tunnel status only when connecting or reasserting to pick up the next relay,
diff --git a/ios/MullvadVPN/TunnelManager/UpdateAccountDataOperation.swift b/ios/MullvadVPN/TunnelManager/UpdateAccountDataOperation.swift
index e0e4f5229d..00531bc2e0 100644
--- a/ios/MullvadVPN/TunnelManager/UpdateAccountDataOperation.swift
+++ b/ios/MullvadVPN/TunnelManager/UpdateAccountDataOperation.swift
@@ -12,7 +12,7 @@ import MullvadREST
 import MullvadTypes
 import Operations
 
-class UpdateAccountDataOperation: ResultOperation<Void, Error> {
+class UpdateAccountDataOperation: ResultOperation<Void> {
     private let logger = Logger(label: "UpdateAccountDataOperation")
     private let interactor: TunnelInteractor
     private let accountsProxy: REST.AccountsProxy
@@ -31,16 +31,16 @@ class UpdateAccountDataOperation: ResultOperation<Void, Error> {
 
     override func main() {
         guard case let .loggedIn(accountData, _) = interactor.deviceState else {
-            finish(completion: .failure(InvalidDeviceStateError()))
+            finish(result: .failure(InvalidDeviceStateError()))
             return
         }
 
         task = accountsProxy.getAccountData(
             accountNumber: accountData.number,
             retryStrategy: .default
-        ) { completion in
+        ) { result in
             self.dispatchQueue.async {
-                self.didReceiveAccountData(completion: completion)
+                self.didReceiveAccountData(result: result)
             }
         }
     }
@@ -50,15 +50,14 @@ class UpdateAccountDataOperation: ResultOperation<Void, Error> {
         task = nil
     }
 
-    private func didReceiveAccountData(
-        completion: OperationCompletion<REST.AccountData, REST.Error>
-    ) {
-        let mappedCompletion = completion.mapError { error -> Error in
+    private func didReceiveAccountData(result: Result<REST.AccountData, Error>) {
+        let result = result.inspectError { error in
+            guard !error.isOperationCancellationError else { return }
+
             self.logger.error(
                 error: error,
                 message: "Failed to fetch account expiry."
             )
-            return error
         }.tryMap { accountData in
             switch interactor.deviceState {
             case .loggedIn(var storedAccountData, let storedDeviceData):
@@ -73,6 +72,6 @@ class UpdateAccountDataOperation: ResultOperation<Void, Error> {
             }
         }
 
-        finish(completion: mappedCompletion)
+        finish(result: result)
     }
 }
diff --git a/ios/MullvadVPN/TunnelManager/UpdateDeviceDataOperation.swift b/ios/MullvadVPN/TunnelManager/UpdateDeviceDataOperation.swift
index 877b654b55..2f0f276153 100644
--- a/ios/MullvadVPN/TunnelManager/UpdateDeviceDataOperation.swift
+++ b/ios/MullvadVPN/TunnelManager/UpdateDeviceDataOperation.swift
@@ -13,7 +13,7 @@ import MullvadTypes
 import Operations
 import class WireGuardKitTypes.PublicKey
 
-class UpdateDeviceDataOperation: ResultOperation<StoredDeviceData, Error> {
+class UpdateDeviceDataOperation: ResultOperation<StoredDeviceData> {
     private let interactor: TunnelInteractor
     private let devicesProxy: REST.DevicesProxy
 
@@ -32,7 +32,7 @@ class UpdateDeviceDataOperation: ResultOperation<StoredDeviceData, Error> {
 
     override func main() {
         guard case let .loggedIn(accountData, deviceData) = interactor.deviceState else {
-            finish(completion: .failure(InvalidDeviceStateError()))
+            finish(result: .failure(InvalidDeviceStateError()))
             return
         }
 
@@ -40,11 +40,9 @@ class UpdateDeviceDataOperation: ResultOperation<StoredDeviceData, Error> {
             accountNumber: accountData.number,
             identifier: deviceData.identifier,
             retryStrategy: .default,
-            completion: { [weak self] completion in
+            completion: { [weak self] result in
                 self?.dispatchQueue.async {
-                    self?.didReceiveDeviceResponse(
-                        completion: completion
-                    )
+                    self?.didReceiveDeviceResponse(result: result)
                 }
             }
         )
@@ -55,23 +53,21 @@ class UpdateDeviceDataOperation: ResultOperation<StoredDeviceData, Error> {
         task = nil
     }
 
-    private func didReceiveDeviceResponse(completion: OperationCompletion<REST.Device, REST.Error>)
-    {
-        let mappedCompletion = completion
-            .tryMap { device -> StoredDeviceData in
-                switch interactor.deviceState {
-                case .loggedIn(let storedAccount, var storedDevice):
-                    storedDevice.update(from: device)
-                    let newDeviceState = DeviceState.loggedIn(storedAccount, storedDevice)
-                    interactor.setDeviceState(newDeviceState, persist: true)
+    private func didReceiveDeviceResponse(result: Result<REST.Device, Error>) {
+        let result = result.tryMap { device -> StoredDeviceData in
+            switch interactor.deviceState {
+            case .loggedIn(let storedAccount, var storedDevice):
+                storedDevice.update(from: device)
+                let newDeviceState = DeviceState.loggedIn(storedAccount, storedDevice)
+                interactor.setDeviceState(newDeviceState, persist: true)
 
-                    return storedDevice
+                return storedDevice
 
-                default:
-                    throw InvalidDeviceStateError()
-                }
+            default:
+                throw InvalidDeviceStateError()
             }
+        }
 
-        finish(completion: mappedCompletion)
+        finish(result: result)
     }
 }
diff --git a/ios/Operations/AsyncOperation.swift b/ios/Operations/AsyncOperation.swift
index 61630573d3..2939f0708e 100644
--- a/ios/Operations/AsyncOperation.swift
+++ b/ios/Operations/AsyncOperation.swift
@@ -188,9 +188,10 @@ open class AsyncOperation: Operation {
 
     public func addCondition(_ condition: OperationCondition) {
         operationLock.lock()
+        defer { operationLock.unlock() }
+
         assert(state < .evaluatingConditions)
         _conditions.append(condition)
-        operationLock.unlock()
     }
 
     private func evaluateConditions() {
diff --git a/ios/Operations/InputInjectionBuilder.swift b/ios/Operations/InputInjectionBuilder.swift
index a4c63a6a00..0c87ab767a 100644
--- a/ios/Operations/InputInjectionBuilder.swift
+++ b/ios/Operations/InputInjectionBuilder.swift
@@ -56,15 +56,15 @@ public final class InputInjectionBuilder<OperationType, Context>
         return self
     }
 
-    public func injectCompletion<T, Success, Failure>(
+    public func injectResult<T, Success>(
         from dependency: T,
-        via block: @escaping (inout Context, T.Completion) -> Void
+        via block: @escaping (inout Context, Result<T.Output, Error>) -> Void
     ) -> Self
-        where T: ResultOperation<Success, Failure>
+        where T: ResultOperation<Success>
     {
         inputBlocks.append { context in
-            if let completion = dependency.completion {
-                block(&context, completion)
+            if let result = dependency.result {
+                block(&context, result)
             }
         }
 
diff --git a/ios/Operations/OperationCompletion.swift b/ios/Operations/OperationCompletion.swift
deleted file mode 100644
index 49a34e0884..0000000000
--- a/ios/Operations/OperationCompletion.swift
+++ /dev/null
@@ -1,159 +0,0 @@
-//
-//  OperationCompletion.swift
-//  Operations
-//
-//  Created by pronebird on 24/01/2022.
-//  Copyright © 2022 Mullvad VPN AB. All rights reserved.
-//
-
-import Foundation
-
-public enum OperationCompletion<Success, Failure: Error> {
-    case cancelled
-    case success(Success)
-    case failure(Failure)
-
-    public var isSuccess: Bool {
-        if case .success = self {
-            return true
-        } else {
-            return false
-        }
-    }
-
-    public var value: Success? {
-        if case let .success(value) = self {
-            return value
-        } else {
-            return nil
-        }
-    }
-
-    public var error: Failure? {
-        if case let .failure(error) = self {
-            return error
-        } else {
-            return nil
-        }
-    }
-
-    public var result: Result<Success, Failure>? {
-        switch self {
-        case let .success(value):
-            return .success(value)
-        case let .failure(error):
-            return .failure(error)
-        case .cancelled:
-            return nil
-        }
-    }
-
-    public init(result: Result<Success, Failure>) {
-        switch result {
-        case let .success(value):
-            self = .success(value)
-        case let .failure(error):
-            self = .failure(error)
-        }
-    }
-
-    public init(error: Failure?) where Success == Void {
-        if let error = error {
-            self = .failure(error)
-        } else {
-            self = .success(())
-        }
-    }
-
-    public func get() throws -> Success {
-        if let result = result {
-            return try result.get()
-        } else {
-            throw OperationCancellationError()
-        }
-    }
-
-    public func map<NewSuccess>(_ block: (Success) -> NewSuccess)
-        -> OperationCompletion<NewSuccess, Failure>
-    {
-        switch self {
-        case let .success(value):
-            return .success(block(value))
-        case let .failure(error):
-            return .failure(error)
-        case .cancelled:
-            return .cancelled
-        }
-    }
-
-    public func mapError<NewFailure: Error>(_ block: (Failure) -> NewFailure)
-        -> OperationCompletion<Success, NewFailure>
-    {
-        switch self {
-        case let .success(value):
-            return .success(value)
-        case let .failure(error):
-            return .failure(block(error))
-        case .cancelled:
-            return .cancelled
-        }
-    }
-
-    public func flatMap<NewSuccess>(_ block: (Success) -> OperationCompletion<NewSuccess, Failure>)
-        -> OperationCompletion<NewSuccess, Failure>
-    {
-        switch self {
-        case let .success(value):
-            return block(value)
-        case let .failure(error):
-            return .failure(error)
-        case .cancelled:
-            return .cancelled
-        }
-    }
-
-    public func flatMapError<NewFailure: Error>(
-        _ block: (Failure)
-            -> OperationCompletion<Success, NewFailure>
-    ) -> OperationCompletion<Success, NewFailure> {
-        switch self {
-        case let .success(value):
-            return .success(value)
-        case let .failure(error):
-            return block(error)
-        case .cancelled:
-            return .cancelled
-        }
-    }
-
-    public func tryMap<NewSuccess>(_ block: (Success) throws -> NewSuccess)
-        -> OperationCompletion<NewSuccess, Error>
-    {
-        switch self {
-        case let .success(value):
-            do {
-                return .success(try block(value))
-            } catch {
-                return .failure(error)
-            }
-        case let .failure(error):
-            return .failure(error)
-        case .cancelled:
-            return .cancelled
-        }
-    }
-
-    public func ignoreOutput() -> OperationCompletion<Void, Failure> {
-        return map { _ in () }
-    }
-
-    public func eraseFailureType() -> OperationCompletion<Success, Error> {
-        return mapError { $0 }
-    }
-}
-
-public struct OperationCancellationError: LocalizedError {
-    public var errorDescription: String? {
-        return "Operation was cancelled."
-    }
-}
diff --git a/ios/Operations/OperationError.swift b/ios/Operations/OperationError.swift
new file mode 100644
index 0000000000..3b96cf6c82
--- /dev/null
+++ b/ios/Operations/OperationError.swift
@@ -0,0 +1,32 @@
+//
+//  OperationError.swift
+//  Operations
+//
+//  Created by pronebird on 24/01/2022.
+//  Copyright © 2022 Mullvad VPN AB. All rights reserved.
+//
+
+import Foundation
+
+public enum OperationError: LocalizedError, Equatable {
+    /// Unsatisfied operation requirement.
+    case unsatisfiedRequirement
+
+    /// Operation cancelled.
+    case cancelled
+
+    public var errorDescription: String? {
+        switch self {
+        case .unsatisfiedRequirement:
+            return "Unsatisfied operation requirement."
+        case .cancelled:
+            return "Operation was cancelled."
+        }
+    }
+}
+
+extension Error {
+    public var isOperationCancellationError: Bool {
+        return (self as? OperationError) == .cancelled
+    }
+}
diff --git a/ios/Operations/ResultBlockOperation.swift b/ios/Operations/ResultBlockOperation.swift
index 9329a566e1..5f21cd202e 100644
--- a/ios/Operations/ResultBlockOperation.swift
+++ b/ios/Operations/ResultBlockOperation.swift
@@ -8,11 +8,8 @@
 
 import Foundation
 
-public final class ResultBlockOperation<Success, Failure: Error>: ResultOperation<
-    Success,
-    Failure
-> {
-    public typealias ExecutionBlock = (ResultBlockOperation<Success, Failure>) -> Void
+public final class ResultBlockOperation<Success>: ResultOperation<Success> {
+    public typealias ExecutionBlock = (ResultBlockOperation<Success>) -> Void
     public typealias ThrowingExecutionBlock = () throws -> Success
 
     private var executionBlock: ExecutionBlock?
@@ -78,10 +75,7 @@ public final class ResultBlockOperation<Success, Failure: Error>: ResultOperatio
         executionBlock = nil
     }
 
-    public func setExecutionBlock(
-        _ block: @escaping (ResultBlockOperation<Success, Failure>)
-            -> Void
-    ) {
+    public func setExecutionBlock(_ block: @escaping ExecutionBlock) {
         dispatchQueue.async {
             assert(!self.isExecuting && !self.isFinished)
             self.executionBlock = block
@@ -106,15 +100,9 @@ public final class ResultBlockOperation<Success, Failure: Error>: ResultOperatio
         -> ExecutionBlock
     {
         return { operation in
-            do {
-                let value = try executionBlock()
-
-                operation.finish(completion: .success(value))
-            } catch {
-                let castedError = error as! Failure
+            let result = Result { try executionBlock() }
 
-                operation.finish(completion: .failure(castedError))
-            }
+            operation.finish(result: result)
         }
     }
 }
diff --git a/ios/Operations/ResultOperation+Output.swift b/ios/Operations/ResultOperation+Output.swift
deleted file mode 100644
index ba31220a46..0000000000
--- a/ios/Operations/ResultOperation+Output.swift
+++ /dev/null
@@ -1,15 +0,0 @@
-//
-//  ResultOperation+Output.swift
-//  Operations
-//
-//  Created by pronebird on 31/05/2022.
-//  Copyright © 2022 Mullvad VPN AB. All rights reserved.
-//
-
-import Foundation
-
-extension ResultOperation: OutputOperation {
-    public var output: Success? {
-        return completion?.value
-    }
-}
diff --git a/ios/Operations/ResultOperation.swift b/ios/Operations/ResultOperation.swift
index 9be0f1c0f4..c884ceb9b2 100644
--- a/ios/Operations/ResultOperation.swift
+++ b/ios/Operations/ResultOperation.swift
@@ -9,20 +9,27 @@
 import Foundation
 
 /// Base class for operations producing result.
-open class ResultOperation<Success, Failure: Error>: AsyncOperation {
-    public typealias Completion = OperationCompletion<Success, Failure>
-    public typealias CompletionHandler = (Completion) -> Void
+open class ResultOperation<Success>: AsyncOperation, OutputOperation {
+    public typealias CompletionHandler = (Result<Success, Error>) -> Void
 
     private let nslock = NSLock()
-    private var completionValue: Completion?
+    private var _output: Success?
     private var _completionQueue: DispatchQueue?
     private var _completionHandler: CompletionHandler?
     private var pendingFinish = false
 
-    public var completion: Completion? {
+    public var result: Result<Success, Error>? {
         nslock.lock()
         defer { nslock.unlock() }
-        return completionValue
+
+        return _output.map { .success($0) } ?? error.map { .failure($0) }
+    }
+
+    public var output: Success? {
+        nslock.lock()
+        defer { nslock.unlock() }
+
+        return _output
     }
 
     public var completionQueue: DispatchQueue? {
@@ -34,8 +41,9 @@ open class ResultOperation<Success, Failure: Error>: AsyncOperation {
         }
         set {
             nslock.lock()
+            defer { nslock.unlock() }
+
             _completionQueue = newValue
-            nslock.unlock()
         }
     }
 
@@ -72,25 +80,19 @@ open class ResultOperation<Success, Failure: Error>: AsyncOperation {
 
     @available(*, unavailable)
     override public func finish() {
-        _finish(error: nil)
+        _finish(result: .failure(OperationError.cancelled))
     }
 
     @available(*, unavailable)
     override public func finish(error: Error?) {
-        _finish(error: error)
+        _finish(result: .failure(error ?? OperationError.cancelled))
     }
 
-    open func finish(completion: Completion) {
-        nslock.lock()
-        if completionValue == nil {
-            completionValue = completion
-        }
-        nslock.unlock()
-
-        _finish(error: completion.error)
+    open func finish(result: Result<Success, Error>) {
+        _finish(result: result)
     }
 
-    private func _finish(error: Error?) {
+    private func _finish(result: Result<Success, Error>) {
         nslock.lock()
         // Bail if operation is already finishing.
         guard !pendingFinish else {
@@ -108,7 +110,9 @@ open class ResultOperation<Success, Failure: Error>: AsyncOperation {
         _completionHandler = nil
 
         // Copy completion value.
-        let completion = completionValue ?? .cancelled
+        if case let .success(output) = result {
+            _output = output
+        }
 
         // Copy completion queue.
         let completionQueue = _completionQueue
@@ -116,7 +120,12 @@ open class ResultOperation<Success, Failure: Error>: AsyncOperation {
 
         let block = {
             // Call completion handler.
-            completionHandler?(completion)
+            completionHandler?(result)
+
+            var error: Error?
+            if case let .failure(failure) = result {
+                error = failure
+            }
 
             // Finish operation.
             super.finish(error: error)
diff --git a/ios/Operations/TransformOperation.swift b/ios/Operations/TransformOperation.swift
index 58048d1033..0b144707be 100644
--- a/ios/Operations/TransformOperation.swift
+++ b/ios/Operations/TransformOperation.swift
@@ -8,11 +8,8 @@
 
 import Foundation
 
-public final class TransformOperation<Input, Output, Failure: Error>:
-    ResultOperation<Output, Failure>,
-    InputOperation
-{
-    public typealias ExecutionBlock = (Input, TransformOperation<Input, Output, Failure>) -> Void
+public final class TransformOperation<Input, Output>: ResultOperation<Output>, InputOperation {
+    public typealias ExecutionBlock = (Input, TransformOperation<Input, Output>) -> Void
     public typealias ThrowingExecutionBlock = (Input) throws -> Output
     public typealias InputBlock = () -> Input?
 
@@ -69,7 +66,7 @@ public final class TransformOperation<Input, Output, Failure: Error>:
         _input = inputValue
 
         guard let inputValue = inputValue, let executionBlock = executionBlock else {
-            finish(completion: .cancelled)
+            finish(result: .failure(OperationError.unsatisfiedRequirement))
             return
         }
 
@@ -125,15 +122,9 @@ public final class TransformOperation<Input, Output, Failure: Error>:
         -> ExecutionBlock
     {
         return { input, operation in
-            do {
-                let value = try executionBlock(input)
+            let result = Result { try executionBlock(input) }
 
-                operation.finish(completion: .success(value))
-            } catch {
-                let castedError = error as! Failure
-
-                operation.finish(completion: .failure(castedError))
-            }
+            operation.finish(result: result)
         }
     }
 }
diff --git a/ios/OperationsTests/OperationConditionTests.swift b/ios/OperationsTests/OperationConditionTests.swift
index ca4a15f20a..b35e687319 100644
--- a/ios/OperationsTests/OperationConditionTests.swift
+++ b/ios/OperationsTests/OperationConditionTests.swift
@@ -78,7 +78,7 @@ class OperationConditionTests: XCTestCase {
         let expectToNeverExecute = expectation(description: "Expect child to never execute.")
         expectToNeverExecute.isInverted = true
 
-        let parent = ResultBlockOperation<Void, URLError> {
+        let parent = ResultBlockOperation<Void> {
             throw URLError(.badURL)
         }
 
diff --git a/ios/OperationsTests/OperationInputInjectionTests.swift b/ios/OperationsTests/OperationInputInjectionTests.swift
index 828afd2643..559228e348 100644
--- a/ios/OperationsTests/OperationInputInjectionTests.swift
+++ b/ios/OperationsTests/OperationInputInjectionTests.swift
@@ -11,11 +11,11 @@ import XCTest
 
 class OperationInputInjectionTests: XCTestCase {
     func testInject() throws {
-        let provider = ResultBlockOperation<Int, Error> {
+        let provider = ResultBlockOperation<Int> {
             return 1
         }
 
-        let consumer = TransformOperation<Int, Int, Error> { input in
+        let consumer = TransformOperation<Int, Int> { input in
             return input + 1
         }
 
@@ -29,11 +29,11 @@ class OperationInputInjectionTests: XCTestCase {
     }
 
     func testInjectVia() throws {
-        let provider = ResultBlockOperation<Int, Error> {
+        let provider = ResultBlockOperation<Int> {
             return 1
         }
 
-        let consumer = TransformOperation<String, Int, Error> { input in
+        let consumer = TransformOperation<String, Int> { input in
             return Int(input)!
         }
 
@@ -62,15 +62,15 @@ class OperationInputInjectionTests: XCTestCase {
 
         let operationQueue = AsyncOperationQueue()
 
-        let providerA = ResultBlockOperation<Int, Error> {
+        let providerA = ResultBlockOperation<Int> {
             return 1
         }
 
-        let providerB = ResultBlockOperation<Int, Error> {
+        let providerB = ResultBlockOperation<Int> {
             return 2
         }
 
-        let consumer = TransformOperation<Int, String, Error> { input in
+        let consumer = TransformOperation<Int, String> { input in
             return "\(input)"
         }
 
diff --git a/ios/PacketTunnel/PacketTunnelProvider.swift b/ios/PacketTunnel/PacketTunnelProvider.swift
index c8bdfd2ea2..8b59185b90 100644
--- a/ios/PacketTunnel/PacketTunnelProvider.swift
+++ b/ios/PacketTunnel/PacketTunnelProvider.swift
@@ -597,31 +597,37 @@ class PacketTunnelProvider: NEPacketTunnelProvider, TunnelMonitorDelegate {
             var newAccountExpiry: Date?
             var newDeviceRevoked: Bool?
 
-            switch accountOperation.completion {
+            switch accountOperation.result {
             case let .failure(error):
-                self.providerLogger.error(
-                    error: error,
-                    message: "Failed to fetch account data."
-                )
+                if !error.isOperationCancellationError {
+                    self.providerLogger.error(
+                        error: error,
+                        message: "Failed to fetch account data."
+                    )
+                }
 
             case let .success(accountData):
                 newAccountExpiry = accountData.expiry
 
-            case .none, .cancelled: break
+            case .none:
+                break
             }
 
-            switch deviceOperation.completion {
+            switch deviceOperation.result {
             case let .failure(error):
-                if error.compareErrorCode(.deviceNotFound) {
+                if let restError = error as? REST.Error,
+                   restError.compareErrorCode(.deviceNotFound)
+                {
                     newDeviceRevoked = true
-                } else {
+                } else if !error.isOperationCancellationError {
                     self.providerLogger.error(
                         error: error,
                         message: "Failed to fetch device data."
                     )
                 }
 
-            case .none, .cancelled, .success: break
+            case .none, .success:
+                break
             }
 
             if var deviceCheck = self.deviceCheck {
@@ -657,9 +663,9 @@ class PacketTunnelProvider: NEPacketTunnelProvider, TunnelMonitorDelegate {
     }
 
     private func createGetAccountDataOperation(accountNumber: String)
-        -> ResultOperation<REST.AccountData, REST.Error>
+        -> ResultOperation<REST.AccountData>
     {
-        let operation = ResultBlockOperation<REST.AccountData, REST.Error>(
+        let operation = ResultBlockOperation<REST.AccountData>(
             dispatchQueue: dispatchQueue
         )
 
@@ -667,8 +673,8 @@ class PacketTunnelProvider: NEPacketTunnelProvider, TunnelMonitorDelegate {
             let task = self.accountsProxy.getAccountData(
                 accountNumber: accountNumber,
                 retryStrategy: .noRetry
-            ) { completion in
-                operation.finish(completion: completion)
+            ) { result in
+                operation.finish(result: result)
             }
 
             operation.addCancellationBlock {
@@ -680,17 +686,17 @@ class PacketTunnelProvider: NEPacketTunnelProvider, TunnelMonitorDelegate {
     }
 
     private func createGetDeviceDataOperation(accountNumber: String, identifier: String)
-        -> ResultOperation<REST.Device, REST.Error>
+        -> ResultOperation<REST.Device>
     {
-        let operation = ResultBlockOperation<REST.Device, REST.Error>(dispatchQueue: dispatchQueue)
+        let operation = ResultBlockOperation<REST.Device>(dispatchQueue: dispatchQueue)
 
         operation.setExecutionBlock { operation in
             let task = self.devicesProxy.getDevice(
                 accountNumber: accountNumber,
                 identifier: identifier,
                 retryStrategy: .noRetry
-            ) { completion in
-                operation.finish(completion: completion)
+            ) { result in
+                operation.finish(result: result)
             }
 
             operation.addCancellationBlock {