First round of PR review fixes re: concurrency

Package.swift

@@ -38,6 +38,7 @@ let package = Package(
             ],
             swiftSettings: [
                 .define("MOCKING", .when(configuration: .debug)),
+                .enableExperimentalFeature("StrictConcurrency"),
             ]
         ),
         .target(
@@ -46,10 +47,16 @@ let package = Package(
                 .target(name: "InternalUtils"),
                 .product(name: "MapLibre", package: "maplibre-gl-native-distribution"),
                 .product(name: "MapLibreSwiftMacros", package: "maplibre-swift-macros"),
+            ],
+            swiftSettings: [
+                .enableExperimentalFeature("StrictConcurrency"),
             ]
         ),
         .target(
-            name: "InternalUtils"
+            name: "InternalUtils",
+            swiftSettings: [
+                .enableExperimentalFeature("StrictConcurrency"),
+            ]
         ),
 
         // MARK: Tests

Sources/MapLibreSwiftUI/Examples/Layers.swift

@@ -5,6 +5,7 @@ import SwiftUI
 
 // A collection of points with various
 // attributes
+@MainActor
 let pointSource = ShapeSource(identifier: "points") {
     // Uses the DSL to quickly construct point features inline
     MLNPointFeature(coordinate: CLLocationCoordinate2D(latitude: 51.47778, longitude: -0.00139))

Sources/MapLibreSwiftUI/Examples/User Location.swift

@@ -1,6 +1,7 @@
 import CoreLocation
 import SwiftUI
 
+@MainActor
 private let locationManager = StaticLocationManager(initialLocation: CLLocation(
     coordinate: switzerland,
     altitude: 0,

Sources/MapLibreSwiftUI/Extensions/MapLibre/MLNMapViewCameraUpdating.swift

@@ -5,15 +5,15 @@ import Mockable
 
 @Mockable
 protocol MLNMapViewCameraUpdating: AnyObject {
-    var userTrackingMode: MLNUserTrackingMode { get set }
-    var minimumPitch: CGFloat { get set }
-    var maximumPitch: CGFloat { get set }
-    func setCenter(_ coordinate: CLLocationCoordinate2D,
-                   zoomLevel: Double,
-                   direction: CLLocationDirection,
-                   animated: Bool)
-    func setZoomLevel(_ zoomLevel: Double, animated: Bool)
-    func setVisibleCoordinateBounds(
+    @MainActor var userTrackingMode: MLNUserTrackingMode { get set }
+    @MainActor var minimumPitch: CGFloat { get set }
+    @MainActor var maximumPitch: CGFloat { get set }
+    @MainActor func setCenter(_ coordinate: CLLocationCoordinate2D,
+                              zoomLevel: Double,
+                              direction: CLLocationDirection,
+                              animated: Bool)
+    @MainActor func setZoomLevel(_ zoomLevel: Double, animated: Bool)
+    @MainActor func setVisibleCoordinateBounds(
         _ bounds: MLNCoordinateBounds,
         edgePadding: UIEdgeInsets,
         animated: Bool,

Sources/MapLibreSwiftUI/Extensions/MapView/MapViewGestures.swift

@@ -9,7 +9,7 @@ extension MapView {
     ///   - mapView: The MLNMapView that will host the gesture itself.
     ///   - context: The UIViewRepresentable context that will orchestrate the response sender
     ///   - gesture: The gesture definition.
-    func registerGesture(_ mapView: MLNMapView, _ context: Context, gesture: MapGesture) {
+    @MainActor func registerGesture(_ mapView: MLNMapView, _ context: Context, gesture: MapGesture) {
         switch gesture.method {
         case let .tap(numberOfTaps: numberOfTaps):
             let gestureRecognizer = UITapGestureRecognizer(target: context.coordinator,
@@ -41,7 +41,7 @@ extension MapView {
     ///   - mapView: The MapView emitting the gesture. This is used to calculate the point and coordinate of the
     /// gesture.
     ///   - sender: The UIGestureRecognizer
-    func processGesture(_ mapView: MLNMapView, _ sender: UIGestureRecognizer) {
+    @MainActor func processGesture(_ mapView: MLNMapView, _ sender: UIGestureRecognizer) {
         guard let gesture = gestures.first(where: { $0.gestureRecognizer == sender }) else {
             assertionFailure("\(sender) is not a registered UIGestureRecongizer on the MapView")
             return
@@ -60,8 +60,8 @@ extension MapView {
     ///   - gesture: The gesture definition for this event.
     ///   - sender: The UIKit gesture emitting from the map view.
     /// - Returns: The calculated context from the sending UIKit gesture
-    func processContextFromGesture(_ mapView: MLNMapView, gesture: MapGesture,
-                                   sender: UIGestureRecognizing) -> MapGestureContext
+    @MainActor func processContextFromGesture(_ mapView: MLNMapView, gesture: MapGesture,
+                                              sender: UIGestureRecognizing) -> MapGestureContext
     {
         // Build the context of the gesture's event.
         let point: CGPoint = switch gesture.method {

Sources/MapLibreSwiftUI/Extensions/UIKit/UIGestureRecognizing.swift

@@ -3,9 +3,9 @@ import UIKit
 
 @Mockable
 protocol UIGestureRecognizing: AnyObject {
-    var state: UIGestureRecognizer.State { get }
-    func location(in view: UIView?) -> CGPoint
-    func location(ofTouch touchIndex: Int, in view: UIView?) -> CGPoint
+    @MainActor var state: UIGestureRecognizer.State { get }
+    @MainActor func location(in view: UIView?) -> CGPoint
+    @MainActor func location(ofTouch touchIndex: Int, in view: UIView?) -> CGPoint
 }
 
 extension UIGestureRecognizer: UIGestureRecognizing {

Sources/MapLibreSwiftUI/MapView.swift

@@ -59,6 +59,7 @@ public struct MapView: UIViewRepresentable {
         context.coordinator.updateCamera(mapView: mapView,
                                          camera: $camera.wrappedValue,
                                          animated: false)
+        mapView.locationManager = mapView.locationManager
 
         // Link the style loaded to the coordinator that emits the delegate event.
         context.coordinator.onStyleLoaded = onStyleLoaded
@@ -88,7 +89,7 @@ public struct MapView: UIViewRepresentable {
                                          animated: isStyleLoaded)
     }
 
-    private func applyModifiers(_ mapView: MLNMapView, runUnsafe: Bool) {
+    @MainActor private func applyModifiers(_ mapView: MLNMapView, runUnsafe: Bool) {
         mapView.contentInset = mapViewContentInset
 
         mapView.logoView.isHidden = isLogoViewHidden

Sources/MapLibreSwiftUI/MapViewCoordinator.swift

@@ -11,6 +11,12 @@ public class MapViewCoordinator: NSObject {
     // every update cycle so we can avoid unnecessary updates
     private var snapshotUserLayers: [StyleLayerDefinition] = []
     private var snapshotCamera: MapViewCamera?
+
+    // Indicates whether we are currently in a push-down camera update cycle.
+    // This is necessary in order to ensure we don't keep trying to reset a state value which we were already processing
+    // an update for.
+    private var isUpdatingCamera = false
+
     var onStyleLoaded: ((MLNStyle) -> Void)?
     var onGesture: (MLNMapView, UIGestureRecognizer) -> Void
 
@@ -41,12 +47,13 @@ public class MapViewCoordinator: NSObject {
     /// camera related MLNMapView functionality.
     ///   - camera: The new camera from the binding.
     ///   - animated: Whether to animate.
-    func updateCamera(mapView: MLNMapViewCameraUpdating, camera: MapViewCamera, animated: Bool) {
+    @MainActor func updateCamera(mapView: MLNMapViewCameraUpdating, camera: MapViewCamera, animated: Bool) {
         guard camera != snapshotCamera else {
             // No action - camera has not changed.
             return
         }
 
+        isUpdatingCamera = true
         switch camera.state {
         case let .centered(onCoordinate: coordinate, zoom: zoom, pitch: pitch, direction: direction):
             mapView.userTrackingMode = .none
@@ -85,11 +92,12 @@ public class MapViewCoordinator: NSObject {
         }
 
         snapshotCamera = camera
+        isUpdatingCamera = false
     }
 
     // MARK: - Coordinator API - Styles + Layers
 
-    func updateStyleSource(_ source: MapStyleSource, mapView: MLNMapView) {
+    @MainActor func updateStyleSource(_ source: MapStyleSource, mapView: MLNMapView) {
         switch (source, parent.styleSource) {
         case let (.url(newURL), .url(oldURL)):
             if newURL != oldURL {
@@ -98,7 +106,7 @@ public class MapViewCoordinator: NSObject {
         }
     }
 
-    func updateLayers(mapView: MLNMapView) {
+    @MainActor func updateLayers(mapView: MLNMapView) {
         // TODO: Figure out how to selectively update layers when only specific props changed. New function in addition to makeMLNStyleLayer?
 
         // TODO: Extract this out into a separate function or three...
@@ -195,35 +203,48 @@ extension MapViewCoordinator: MLNMapViewDelegate {
 
     /// The MapView's region has changed with a specific reason.
     public func mapView(_ mapView: MLNMapView, regionDidChangeWith reason: MLNCameraChangeReason, animated _: Bool) {
+        guard !isUpdatingCamera else {
+            return
+        }
+
         // If any of these are a mismatch, we know the camera is no longer following a desired method, so we should
         // detach and revert to a .centered camera. If any one of these is true, the desired camera state still
         // matches the mapView's userTrackingMode
-        let isProgrammaticallyTracking: Bool = switch parent.camera.state {
-        case .centered(onCoordinate: _):
-            false
-        case .trackingUserLocation:
-            mapView.userTrackingMode == .follow
-        case .trackingUserLocationWithHeading:
-            mapView.userTrackingMode == .followWithHeading
-        case .trackingUserLocationWithCourse:
-            mapView.userTrackingMode == .followWithCourse
-        case .rect(boundingBox: _, edgePadding: _):
-            false
-        case .showcase(shapeCollection: _):
-            false
-        }
+        // NOTE: The use of assumeIsolated is just to make Swift strict concurrency checks happy.
+        // This invariant is upheld by the MLNMapView.
+        MainActor.assumeIsolated {
+            let userTrackingMode = mapView.userTrackingMode
+            let isProgrammaticallyTracking: Bool = switch parent.camera.state {
+            case .trackingUserLocation:
+                userTrackingMode == .follow
+            case .trackingUserLocationWithHeading:
+                userTrackingMode == .followWithHeading
+            case .trackingUserLocationWithCourse:
+                userTrackingMode == .followWithCourse
+            case .centered, .rect, .showcase:
+                false
+            }
 
-        if isProgrammaticallyTracking {
-            // Programmatic tracking is still active, we can ignore camera updates until we unset/fail this boolean
-            // check
-            return
-        }
+            guard !isProgrammaticallyTracking else {
+                // Programmatic tracking is still active, we can ignore camera updates until we unset/fail this boolean
+                // check
+                return
+            }
 
-        DispatchQueue.main.async {
             // Publish the MLNMapView's "raw" camera state to the MapView camera binding.
-            self.parent.camera = .center(mapView.centerCoordinate,
-                                         zoom: mapView.zoomLevel,
-                                         reason: CameraChangeReason(reason))
+            // This path only executes when the map view diverges from the parent state, so this is a "matter of fact"
+            // state propagation.
+            let newCamera: MapViewCamera = .center(mapView.centerCoordinate,
+                                                   zoom: mapView.zoomLevel,
+                                                   // TODO: Pitch doesn't really describe current state
+                                                   pitch: .freeWithinRange(
+                                                       minimum: mapView.minimumPitch,
+                                                       maximum: mapView.maximumPitch
+                                                   ),
+                                                   direction: mapView.direction,
+                                                   reason: CameraChangeReason(reason))
+            snapshotCamera = newCamera
+            self.parent.camera = newCamera
         }
     }
 }

Sources/MapLibreSwiftUI/Models/MapCamera/CameraPitch.swift

@@ -2,7 +2,7 @@ import Foundation
 import MapLibre
 
 /// The current pitch state for the MapViewCamera
-public enum CameraPitch: Hashable {
+public enum CameraPitch: Hashable, Sendable {
     /// The user is free to control pitch from it's default min to max.
     case free
 

Sources/MapLibreSwiftUI/StaticLocationManager.swift

@@ -11,31 +11,20 @@ import MapLibre
 /// You can provide a new location by setting the ``lastLocation`` property.
 ///
 /// This class does not ever perform any authorization checks. That is the responsiblity of the caller.
-public class StaticLocationManager: NSObject {
-    public var delegate: (any MLNLocationManagerDelegate)? = nil {
-        didSet {
-            DispatchQueue.main.async {
-                self.delegate?.locationManagerDidChangeAuthorization(self)
-                self.delegate?.locationManager(self, didUpdate: [self.lastLocation])
-            }
-        }
-    }
+public final class StaticLocationManager: NSObject, @unchecked Sendable {
+    public var delegate: (any MLNLocationManagerDelegate)?
 
     public var authorizationStatus: CLAuthorizationStatus = .authorizedAlways {
         didSet {
-            DispatchQueue.main.async {
-                self.delegate?.locationManagerDidChangeAuthorization(self)
-            }
+            delegate?.locationManagerDidChangeAuthorization(self)
         }
     }
 
     public var headingOrientation: CLDeviceOrientation = .portrait
 
     public var lastLocation: CLLocation {
         didSet {
-            DispatchQueue.main.async {
-                self.delegate?.locationManager(self, didUpdate: [self.lastLocation])
-            }
+            delegate?.locationManager(self, didUpdate: [lastLocation])
         }
     }
 
@@ -54,7 +43,13 @@ extension StaticLocationManager: MLNLocationManager {
     }
 
     public func startUpdatingLocation() {
-        // Do nothing
+        // This has to be async dispatched or else the map view will not update immediately if the camera is set to
+        // follow the user's location. This leads to some REALLY (unbearably) bad artifacts. We should find a better
+        // solution for this at some point. This is the reason for the @unchecked Sendable conformance by the way (so
+        // that we don't get a warning about using non-sendable self; it should be safe though).
+        DispatchQueue.main.async {
+            self.delegate?.locationManager(self, didUpdate: [self.lastLocation])
+        }
     }
 
     public func stopUpdatingLocation() {

Tests/MapLibreSwiftUITests/MapView/MapViewGestureTests.swift

@@ -27,7 +27,7 @@ final class MapViewGestureTests: XCTestCase {
 
     // MARK: Gesture Processing
 
-    func testTapGesture() {
+    @MainActor func testTapGesture() {
         let gesture = MapGesture(method: .tap(numberOfTaps: 2)) { _ in
             // Do nothing
         }
@@ -52,7 +52,7 @@ final class MapViewGestureTests: XCTestCase {
         XCTAssertEqual(result.coordinate.longitude, -15, accuracy: 1)
     }
 
-    func testLongPressGesture() {
+    @MainActor func testLongPressGesture() {
         let gesture = MapGesture(method: .longPress(minimumDuration: 1)) { _ in
             // Do nothing
         }

Tests/MapLibreSwiftUITests/MapViewCoordinator/MapViewCoordinatorCameraTests.swift

@@ -16,7 +16,7 @@ final class MapViewCoordinatorCameraTests: XCTestCase {
         }
     }
 
-    func testUnchangedCamera() {
+    @MainActor func testUnchangedCamera() {
         let camera: MapViewCamera = .default()
 
         coordinator.updateCamera(mapView: maplibreMapView, camera: camera, animated: false)
@@ -50,7 +50,7 @@ final class MapViewCoordinatorCameraTests: XCTestCase {
             .called(count: 0)
     }
 
-    func testCenterCameraUpdate() {
+    @MainActor func testCenterCameraUpdate() {
         let coordinate = CLLocationCoordinate2D(latitude: 12.3, longitude: 23.4)
         let newCamera: MapViewCamera = .center(coordinate, zoom: 13)
 
@@ -80,7 +80,7 @@ final class MapViewCoordinatorCameraTests: XCTestCase {
             .called(count: 0)
     }
 
-    func testUserTrackingCameraUpdate() {
+    @MainActor func testUserTrackingCameraUpdate() {
         let newCamera: MapViewCamera = .trackUserLocation()
 
         coordinator.updateCamera(mapView: maplibreMapView, camera: newCamera, animated: false)
@@ -109,7 +109,7 @@ final class MapViewCoordinatorCameraTests: XCTestCase {
             .called(count: 1)
     }
 
-    func testUserTrackingWithCourseCameraUpdate() {
+    @MainActor func testUserTrackingWithCourseCameraUpdate() {
         let newCamera: MapViewCamera = .trackUserLocationWithCourse()
 
         coordinator.updateCamera(mapView: maplibreMapView, camera: newCamera, animated: false)
@@ -138,7 +138,7 @@ final class MapViewCoordinatorCameraTests: XCTestCase {
             .called(count: 1)
     }
 
-    func testUserTrackingWithHeadingUpdate() {
+    @MainActor func testUserTrackingWithHeadingUpdate() {
         let newCamera: MapViewCamera = .trackUserLocationWithHeading()
 
         coordinator.updateCamera(mapView: maplibreMapView, camera: newCamera, animated: false)