fix: requestAlwaysAuthorization sometimes doesn't return

humblehacker · humblehacker · commit 5d217891ba21 · 2022-11-29T09:41:24.000-08:00
In some circumstances, requesting location permission has no effect. When this happens, the call to request permission never returns. This fix uses the UIApplication state as a proxy for knowing if an authorization dialog has been shown, and when it has been dismissed so we can return a value in the case that the dialog is never shown. fixes #30
diff --git a/Sources/AsyncLocationKit/ApplicationStateMonitor.swift b/Sources/AsyncLocationKit/ApplicationStateMonitor.swift
@@ -0,0 +1,98 @@
+//
+//  ApplicationStateMonitor.swift
+//  AsyncLocationKit
+//
+//  Created by David Whetstone on 11/28/22.
+//
+
+import Foundation
+import UIKit
+
+@MainActor
+class ApplicationStateMonitor {
+    private(set) var hasResignedActive = false
+
+    private var hasResignedActiveTask: Task<Void, Never>?
+    private var hasBecomeActiveTask: Task<Void, Never>?
+
+    func startMonitoringApplicationState() {
+        guard #available(macOS 12, iOS 15, tvOS 15, watchOS 8, *) else { return }
+        startMonitoringHasResignedActive()
+        startMonitoringHasBecomeActive()
+    }
+
+    func stopMonitoringApplicationState() {
+        guard #available(macOS 12, iOS 15, tvOS 15, watchOS 8, *) else { return }
+        stopMonitoringHasResignedActive()
+        stopMonitoringHasBecomeActive()
+    }
+
+    func hasResignedActive() async -> Bool {
+        guard #available(macOS 12, iOS 15, tvOS 15, watchOS 8, *) else { return false }
+        var iter = hasResignedActiveSequence.makeAsyncIterator()
+        return await iter.next() != nil
+    }
+
+    func hasBecomeActive() async -> Bool {
+        guard #available(macOS 12, iOS 15, tvOS 15, watchOS 8, *) else { return false }
+        var iter = hasBecomeActiveSequence.makeAsyncIterator()
+        return await iter.next() != nil
+    }
+
+    @available(macOS 12, iOS 15, tvOS 15, watchOS 8, *)
+    private func startMonitoringHasResignedActive() {
+        guard hasResignedActiveTask == nil else { return }
+
+        hasResignedActiveTask = Task {
+            for await _ in self.hasResignedActiveSequence {
+                if Task.isCancelled { break }
+                self.hasResignedActive = true
+                self.stopMonitoringHasResignedActive()
+            }
+        }
+    }
+
+    @available(macOS 12, iOS 15, tvOS 15, watchOS 8, *)
+    private func startMonitoringHasBecomeActive() {
+        guard hasBecomeActiveTask == nil else { return }
+
+        hasBecomeActiveTask = Task {
+            for await _ in self.hasBecomeActiveSequence {
+                if Task.isCancelled { break }
+                self.stopMonitoringHasBecomeActive()
+            }
+        }
+    }
+
+    private func stopMonitoringHasResignedActive() {
+        hasResignedActiveTask?.cancel()
+        hasResignedActiveTask = nil
+    }
+
+    private func stopMonitoringHasBecomeActive() {
+        hasBecomeActiveTask?.cancel()
+        hasBecomeActiveTask = nil
+    }
+
+    @available(macOS 12, iOS 15, tvOS 15, watchOS 8, *)
+    private var hasResignedActiveSequence: AsyncMapSequence<NotificationCenter.Notifications, Bool> {
+        _hasResignedActiveSequence as! AsyncMapSequence<NotificationCenter.Notifications, Bool>
+    }
+
+    @available(macOS 12, iOS 15, tvOS 15, watchOS 8, *)
+    private var hasBecomeActiveSequence: AsyncMapSequence<NotificationCenter.Notifications, Bool> {
+        _hasBecomeActiveSequence as! AsyncMapSequence<NotificationCenter.Notifications, Bool>
+    }
+
+    // We unfortunately need these backing variables since properties cannot be declared conditionally available
+
+    private var _hasResignedActiveSequence: Any? = {
+        guard #available(macOS 12, iOS 15, tvOS 15, watchOS 8, *) else { return nil }
+        return NotificationCenter.default.notifications(named: UIApplication.willResignActiveNotification).map { _ in true }
+    }()
+
+    private var _hasBecomeActiveSequence: Any? = {
+        guard #available(macOS 12, iOS 15, tvOS 15, watchOS 8, *) else { return nil }
+        return NotificationCenter.default.notifications(named: UIApplication.didBecomeActiveNotification).map { _ in true }
+    }()
+}
diff --git a/Sources/AsyncLocationKit/AsyncLocationManager.swift b/Sources/AsyncLocationKit/AsyncLocationManager.swift
@@ -59,8 +59,7 @@ public final class AsyncLocationManager {
         // Though undocumented, `locationServicesEnabled()` must not be called from the main thread. Otherwise,
         // we get a runtime warning "This method can cause UI unresponsiveness if invoked on the main thread"
         // Therefore, we use `Task.detached` to ensure we're off the main thread.
-        // Also, we force `try` as we expect no exceptions to be thrown from `locationServicesEnabled()`
-        try! await Task.detached { CLLocationManager.locationServicesEnabled() }.value
+        await Task.detached { CLLocationManager.locationServicesEnabled() }.value
     }
 
     @available(watchOS 6.0, *)
@@ -133,7 +132,7 @@ public final class AsyncLocationManager {
     @available(*, deprecated, message: "Use new function requestPermission(with:)")
     @available(watchOS 7.0, *)
     public func requestAuthorizationWhenInUse() async -> CLAuthorizationStatus {
-        let authorizationPerformer = RequestAuthorizationPerformer()
+        let authorizationPerformer = RequestAuthorizationPerformer(currentStatus: getAuthorizationStatus())
         return await withTaskCancellationHandler(operation: {
             await withCheckedContinuation { continuation in
                 let authorizationStatus = getAuthorizationStatus()
@@ -155,7 +154,7 @@ public final class AsyncLocationManager {
     @available(watchOS 7.0, *)
     @available(iOS 14, *)
     public func requestAuthorizationAlways() async -> CLAuthorizationStatus {
-        let authorizationPerformer = RequestAuthorizationPerformer()
+        let authorizationPerformer = RequestAuthorizationPerformer(currentStatus: getAuthorizationStatus())
         return await withTaskCancellationHandler(operation: {
             await withCheckedContinuation { continuation in
 #if os(macOS)
@@ -316,7 +315,7 @@ public final class AsyncLocationManager {
 
 extension AsyncLocationManager {
     private func locationPermissionWhenInUse() async -> CLAuthorizationStatus {
-        let authorizationPerformer = RequestAuthorizationPerformer()
+        let authorizationPerformer = RequestAuthorizationPerformer(currentStatus: getAuthorizationStatus())
         return await withTaskCancellationHandler(operation: {
             await withCheckedContinuation { continuation in
                 let authorizationStatus = getAuthorizationStatus()
@@ -334,7 +333,7 @@ extension AsyncLocationManager {
     }
     
     private func locationPermissionAlways() async -> CLAuthorizationStatus {
-        let authorizationPerformer = RequestAuthorizationPerformer()
+        let authorizationPerformer = RequestAuthorizationPerformer(currentStatus: getAuthorizationStatus())
         return await withTaskCancellationHandler(operation: {
             await withCheckedContinuation { continuation in
 #if os(macOS)
@@ -379,6 +378,14 @@ extension AsyncLocationManager {
                             continuation.resume(with: .failure(error))
                             return
                         }
+
+                        // If the user chooses reduced accuracy, the didChangeAuthorization delegate method
+                        // will not called. So we must emulate that here.
+                        if self.locationManager.accuracyAuthorization == .reducedAccuracy {
+                            self.proxyDelegate.eventForMethodInvoked(
+                                .didChangeAccuracyAuthorization(authorization: self.locationManager.accuracyAuthorization)
+                            )
+                        }
                     }
                 }
             }
@@ -387,3 +394,27 @@ extension AsyncLocationManager {
         })
     }
 }
+
+extension CLAuthorizationStatus: CustomStringConvertible {
+    public var description: String {
+        switch self {
+        case .notDetermined: return ".notDetermined"
+        case .restricted: return ".restricted"
+        case .denied: return ".denied"
+        case .authorizedWhenInUse: return ".authorizedWhenInUse"
+        case .authorizedAlways: return ".authorisedAlways"
+        @unknown default: return "unknown \(rawValue)"
+        }
+    }
+}
+
+extension CLAccuracyAuthorization: CustomStringConvertible {
+    public var description: String {
+        switch self {
+        case .fullAccuracy: return ".fullAccuracy"
+        case .reducedAccuracy: return ".reducedAccuracy"
+        @unknown default: return "unknown \(rawValue)"
+        }
+    }
+}
+
diff --git a/Sources/AsyncLocationKit/Performers/AuthorizationPerformer.swift b/Sources/AsyncLocationKit/Performers/AuthorizationPerformer.swift
@@ -24,6 +24,13 @@ import Foundation
 import CoreLocation.CLLocation
 
 class RequestAuthorizationPerformer: AnyLocationPerformer {
+    private let currentStatus: CLAuthorizationStatus
+    private var applicationStateMonitor: ApplicationStateMonitor!
+
+    init(currentStatus: CLAuthorizationStatus) {
+        self.currentStatus = currentStatus
+    }
+
     var typeIdentifier: ObjectIdentifier {
         return ObjectIdentifier(Self.self)
     }
@@ -38,8 +45,29 @@ class RequestAuthorizationPerformer: AnyLocationPerformer {
     
     func linkContinuation(_ continuation: AuthotizationContinuation) {
         self.continuation = continuation
+        Task { await start() }
     }
-    
+
+    func start() async {
+        applicationStateMonitor = await ApplicationStateMonitor()
+        await applicationStateMonitor.startMonitoringApplicationState()
+
+        // Wait a brief amount of time for the permission dialog to appear.
+        Task { [applicationStateMonitor, currentStatus] in
+            guard let applicationStateMonitor else { return }
+            try await Task.sleep(nanoseconds: UInt64(Double(NSEC_PER_SEC) * 0.3))
+
+            if await !applicationStateMonitor.hasResignedActive {
+                // We timed out waiting for the dialog to appear, so we can assume that the permission request
+                // silently failed. We then emit the `currentStatus` to be returned to the caller.
+                await applicationStateMonitor.stopMonitoringApplicationState()
+                await MainActor.run {
+                    self.invokedMethod(event:.didChangeAuthorization(status: currentStatus))
+                }
+            }
+        }
+    }
+
     func eventSupported(_ event: CoreLocationDelegateEvent) -> Bool {
         return eventsSupport.contains(event.rawEvent())
     }
@@ -48,15 +76,26 @@ class RequestAuthorizationPerformer: AnyLocationPerformer {
         switch event {
         case .didChangeAuthorization(let status):
             if status != .notDetermined {
-                guard let continuation = continuation else { cancellabel?.cancel(for: self); return }
-                continuation.resume(returning: status)
-                self.continuation = nil
-                cancellabel?.cancel(for: self)
+                Task {
+                    if await applicationStateMonitor.hasResignedActive {
+                        _ = await applicationStateMonitor.hasBecomeActive()
+                    }
+
+                    guard let continuation = continuation else { cancellabel?.cancel(for: self); return }
+                    continuation.resume(returning: status)
+                    self.continuation = nil
+                    cancellabel?.cancel(for: self)
+                }
             }
         default:
             fatalError("Method can't be execute by this performer: \(String(describing: self)) for event: \(type(of: event))")
         }
     }
-    
-    func cancelation() { }
+
+    func cancelation() {
+        Task {
+            await applicationStateMonitor.stopMonitoringApplicationState()
+        }
+    }
 }
+
