Ensure thread safety

Source/Bridge.swift

@@ -18,6 +18,7 @@ protocol Bridgable: AnyObject {
 /// `Bridge` is the object for configuring a web view and
 /// the channel for sending/receiving messages
 public final class Bridge: Bridgable {
+    public typealias InitializationCompletionHandler = () -> Void
     weak var delegate: BridgeDelegate?
     weak var webView: WKWebView?
 
@@ -26,38 +27,38 @@ public final class Bridge: Bridgable {
             initialize(Bridge(webView: webView))
         }
     }
-
+    
     init(webView: WKWebView) {
         self.webView = webView
         loadIntoWebView()
     }
 
-    deinit {
-        webView?.configuration.userContentController.removeScriptMessageHandler(forName: scriptHandlerName)
-    }
-
     // MARK: - Internal API
 
     /// Register a single component
     /// - Parameter component: Name of a component to register support for
+    @MainActor 
     func register(component: String) async throws {
         try await callBridgeFunction(.register, arguments: [component])
     }
 
     /// Register multiple components
     /// - Parameter components: Array of component names to register
+    @MainActor 
     func register(components: [String]) async throws {
         try await callBridgeFunction(.register, arguments: [components])
     }
 
     /// Unregister support for a single component
     /// - Parameter component: Component name
+    @MainActor 
     func unregister(component: String) async throws {
         try await callBridgeFunction(.unregister, arguments: [component])
     }
 
     /// Send a message through the bridge to the web application
     /// - Parameter message: Message to send
+    @MainActor
     func reply(with message: Message) async throws {
         logger.debug("bridgeWillReplyWithMessage: \(String(describing: message))")
         let internalMessage = InternalMessage(from: message)
@@ -72,15 +73,15 @@ public final class Bridge: Bridgable {
 //        let replyMessage = message.replacing(data: data)
 //        callBridgeFunction("send", arguments: [replyMessage.toJSON()])
 //    }
-    @MainActor
     @discardableResult
-    func evaluate(javaScript: String) async throws -> Any {
+    @MainActor
+    func evaluate(javaScript: String) async throws -> Any? {
         guard let webView else {
             throw BridgeError.missingWebView
         }
 
         do {
-            return try await webView.evaluateJavaScript(javaScript)
+            return try await webView.evaluateJavaScriptAsync(javaScript)
         } catch {
             logger.error("Error evaluating JavaScript: \(error)")
             throw error
@@ -90,7 +91,8 @@ public final class Bridge: Bridgable {
     /// Evaluates a JavaScript function with optional arguments by encoding the arguments
     /// Function should not include the parens
     /// Usage: evaluate(function: "console.log", arguments: ["test"])
-    func evaluate(function: String, arguments: [Any] = []) async throws -> Any {
+    @MainActor
+    func evaluate(function: String, arguments: [Any] = []) async throws -> Any? {
         try await evaluate(javaScript: JavaScript(functionName: function, arguments: arguments).toString())
     }
 
@@ -112,6 +114,7 @@ public final class Bridge: Bridgable {
     /// The webkit.messageHandlers name
     private let scriptHandlerName = "strada"
 
+    @MainActor
     private func callBridgeFunction(_ function: JavaScriptBridgeFunction, arguments: [Any]) async throws {
         let js = JavaScript(object: bridgeGlobal, functionName: function.rawValue, arguments: arguments)
         try await evaluate(javaScript: js)
@@ -151,7 +154,8 @@ public final class Bridge: Bridgable {
     // MARK: - JavaScript Evaluation
 
     @discardableResult
-    private func evaluate(javaScript: JavaScript) async throws -> Any {
+    @MainActor
+    private func evaluate(javaScript: JavaScript) async throws -> Any? {
         do {
             return try await evaluate(javaScript: javaScript.toString())
         } catch {
@@ -169,9 +173,9 @@ public final class Bridge: Bridgable {
 
 extension Bridge: ScriptMessageHandlerDelegate {
     @MainActor
-    func scriptMessageHandlerDidReceiveMessage(_ scriptMessage: WKScriptMessage) async throws {
+    func scriptMessageHandlerDidReceiveMessage(_ scriptMessage: WKScriptMessage) {
         if let event = scriptMessage.body as? String, event == "ready" {
-            try await delegate?.bridgeDidInitialize()
+            delegate?.bridgeDidInitialize()
             return
         }
 
@@ -183,3 +187,22 @@ extension Bridge: ScriptMessageHandlerDelegate {
         logger.warning("Unhandled message received: \(String(describing: scriptMessage.body))")
     }
 }
+
+private extension WKWebView {
+    /// NOTE: The async version crashes the app with `Fatal error: Unexpectedly found nil while implicitly unwrapping an Optional value`
+    /// in case the function doesn't return anything.
+    /// This is a workaround. See https://forums.developer.apple.com/forums/thread/701553 for more details.
+    @discardableResult
+    @MainActor
+    func evaluateJavaScriptAsync(_ javaScriptString: String) async throws -> Any? {
+        return try await withCheckedThrowingContinuation { (continuation: CheckedContinuation<Any?, Error>) in
+            evaluateJavaScript(javaScriptString) { data, error in
+                if let error {
+                    continuation.resume(throwing: error)
+                } else {
+                    continuation.resume(returning: data)
+                }
+            }
+        }
+    }
+}

Source/BridgeComponent.swift

@@ -1,5 +1,6 @@
 import Foundation
 
+@MainActor
 protocol BridgingComponent: AnyObject {
     static var name: String { get }
     var delegate: BridgingDelegate { get }
@@ -22,6 +23,7 @@ protocol BridgingComponent: AnyObject {
     func viewDidDisappear()
 }
 
+@MainActor
 open class BridgeComponent: BridgingComponent {
     public typealias ReplyCompletionHandler = (Result<Bool, Error>) -> Void
 
@@ -30,7 +32,7 @@ open class BridgeComponent: BridgingComponent {
     /// Subclasses must provide their own implementation of this property.
     ///
     /// - Note: This property is used for identifying the component.
-    open class var name: String {
+    nonisolated open class var name: String {
         fatalError("BridgeComponent subclass must provide a unique 'name'")
     }
 
@@ -149,7 +151,7 @@ open class BridgeComponent: BridgingComponent {
 
     @discardableResult
     /// Replies to the web with the last received message for a given `event`, replacing its `jsonData`
-    /// with the provided `Encodable` object. 
+    /// with the provided `Encodable` object.
     ///
     /// NOTE: If a message has not been received for the given `event`, the reply will be ignored.
     ///
@@ -275,3 +277,4 @@ open class BridgeComponent: BridgingComponent {
 
     private var receivedMessages = [String: Message]()
 }
+

Source/BridgeDelegate.swift

@@ -3,6 +3,7 @@ import WebKit
 
 public protocol BridgeDestination: AnyObject {}
 
+@MainActor
 public protocol BridgingDelegate: AnyObject {
     var location: String { get }
     var destination: BridgeDestination { get }
@@ -20,10 +21,11 @@ public protocol BridgingDelegate: AnyObject {
 
     func component<C: BridgeComponent>() -> C?
 
-    func bridgeDidInitialize() async throws
+    func bridgeDidInitialize()
     func bridgeDidReceiveMessage(_ message: Message) -> Bool
 }
 
+@MainActor
 public final class BridgeDelegate: BridgingDelegate {
     public let location: String
     public unowned let destination: BridgeDestination
@@ -109,9 +111,15 @@ public final class BridgeDelegate: BridgingDelegate {
 
     // MARK: Internal use
 
-    public func bridgeDidInitialize() async throws {
+    public func bridgeDidInitialize() {
         let componentNames = componentTypes.map { $0.name }
-        try await bridge?.register(components: componentNames)
+        Task {
+            do {
+                try await bridge?.register(components: componentNames)
+            } catch {
+                logger.error("bridgeDidFailToRegisterComponents: \(error)")
+            }
+        }
     }
 
     @discardableResult
@@ -153,4 +161,3 @@ public final class BridgeDelegate: BridgingDelegate {
         return component
     }
 }
-

Source/ScriptMessageHandler.swift

@@ -1,7 +1,7 @@
 import WebKit
 
 protocol ScriptMessageHandlerDelegate: AnyObject {
-    func scriptMessageHandlerDidReceiveMessage(_ scriptMessage: WKScriptMessage) async throws
+    func scriptMessageHandlerDidReceiveMessage(_ scriptMessage: WKScriptMessage)
 }
 
 // Avoids retain cycle caused by WKUserContentController
@@ -13,6 +13,6 @@ final class ScriptMessageHandler: NSObject, WKScriptMessageHandler {
     }
 
     func userContentController(_ userContentController: WKUserContentController, didReceive scriptMessage: WKScriptMessage) {
-        Task { try await delegate?.scriptMessageHandlerDidReceiveMessage(scriptMessage) }
+        delegate?.scriptMessageHandlerDidReceiveMessage(scriptMessage)
     }
 }

Strada.xcodeproj/project.pbxproj

@@ -33,6 +33,7 @@
 		E2DB15912A7163B0001EE08C /* BridgeDelegate.swift in Sources */ = {isa = PBXBuildFile; fileRef = E2DB15902A7163B0001EE08C /* BridgeDelegate.swift */; };
 		E2DB15932A7282CF001EE08C /* BridgeComponent.swift in Sources */ = {isa = PBXBuildFile; fileRef = E2DB15922A7282CF001EE08C /* BridgeComponent.swift */; };
 		E2DB15952A72B0A8001EE08C /* BridgeDelegateTests.swift in Sources */ = {isa = PBXBuildFile; fileRef = E2DB15942A72B0A8001EE08C /* BridgeDelegateTests.swift */; };
+		E2F4E06B2B9095BC000A3A24 /* TimeInterval+ExpectationTimeout.swift in Sources */ = {isa = PBXBuildFile; fileRef = E2F4E06A2B9095BC000A3A24 /* TimeInterval+ExpectationTimeout.swift */; };
 		E2FDCF982A8297DA003D27AE /* BridgeComponentTests.swift in Sources */ = {isa = PBXBuildFile; fileRef = E2FDCF972A8297DA003D27AE /* BridgeComponentTests.swift */; };
 		E2FDCF9B2A829AEE003D27AE /* BridgeSpy.swift in Sources */ = {isa = PBXBuildFile; fileRef = E2FDCF9A2A829AEE003D27AE /* BridgeSpy.swift */; };
 		E2FDCF9D2A829C6F003D27AE /* TestData.swift in Sources */ = {isa = PBXBuildFile; fileRef = E2FDCF9C2A829C6F003D27AE /* TestData.swift */; };
@@ -79,6 +80,7 @@
 		E2DB15902A7163B0001EE08C /* BridgeDelegate.swift */ = {isa = PBXFileReference; lastKnownFileType = sourcecode.swift; path = BridgeDelegate.swift; sourceTree = "<group>"; };
 		E2DB15922A7282CF001EE08C /* BridgeComponent.swift */ = {isa = PBXFileReference; lastKnownFileType = sourcecode.swift; path = BridgeComponent.swift; sourceTree = "<group>"; };
 		E2DB15942A72B0A8001EE08C /* BridgeDelegateTests.swift */ = {isa = PBXFileReference; lastKnownFileType = sourcecode.swift; path = BridgeDelegateTests.swift; sourceTree = "<group>"; };
+		E2F4E06A2B9095BC000A3A24 /* TimeInterval+ExpectationTimeout.swift */ = {isa = PBXFileReference; lastKnownFileType = sourcecode.swift; path = "TimeInterval+ExpectationTimeout.swift"; sourceTree = "<group>"; };
 		E2FDCF972A8297DA003D27AE /* BridgeComponentTests.swift */ = {isa = PBXFileReference; lastKnownFileType = sourcecode.swift; path = BridgeComponentTests.swift; sourceTree = "<group>"; };
 		E2FDCF9A2A829AEE003D27AE /* BridgeSpy.swift */ = {isa = PBXFileReference; lastKnownFileType = sourcecode.swift; path = BridgeSpy.swift; sourceTree = "<group>"; };
 		E2FDCF9C2A829C6F003D27AE /* TestData.swift */ = {isa = PBXFileReference; lastKnownFileType = sourcecode.swift; path = TestData.swift; sourceTree = "<group>"; };
@@ -146,6 +148,7 @@
 		9274F1F22229963B003E85F4 /* Tests */ = {
 			isa = PBXGroup;
 			children = (
+				E2F4E0692B9095A5000A3A24 /* Extensions */,
 				E227FAF12A94D48C00A645E4 /* ComponentTestExample */,
 				E2FDCF9C2A829C6F003D27AE /* TestData.swift */,
 				E2FDCF992A829AD5003D27AE /* Spies */,
@@ -181,6 +184,14 @@
 			path = ComponentTestExample;
 			sourceTree = "<group>";
 		};
+		E2F4E0692B9095A5000A3A24 /* Extensions */ = {
+			isa = PBXGroup;
+			children = (
+				E2F4E06A2B9095BC000A3A24 /* TimeInterval+ExpectationTimeout.swift */,
+			);
+			path = Extensions;
+			sourceTree = "<group>";
+		};
 		E2FDCF992A829AD5003D27AE /* Spies */ = {
 			isa = PBXGroup;
 			children = (
@@ -327,6 +338,7 @@
 			files = (
 				E2DB15952A72B0A8001EE08C /* BridgeDelegateTests.swift in Sources */,
 				E227FAF02A94D34E00A645E4 /* ComposerComponent.swift in Sources */,
+				E2F4E06B2B9095BC000A3A24 /* TimeInterval+ExpectationTimeout.swift in Sources */,
 				E227FAEE2A94B35900A645E4 /* BridgeDelegateSpy.swift in Sources */,
 				C11349C2258801F6000A6E56 /* JavaScriptTests.swift in Sources */,
 				E227FAF32A94D57300A645E4 /* ComposerComponentTests.swift in Sources */,

Tests/BridgeComponentTests.swift

@@ -3,6 +3,7 @@ import XCTest
 import WebKit
 import Strada
 
+@MainActor
 class BridgeComponentTest: XCTestCase {
     private var delegate: BridgeDelegateSpy!
     private var destination: AppBridgeDestination!
@@ -222,7 +223,3 @@ class BridgeComponentTest: XCTestCase {
         wait(for: [expectation], timeout: .expectationTimeout)
     }
 }
-
-private extension TimeInterval {
-    static let expectationTimeout: TimeInterval = 5
-}

Tests/BridgeDelegateTests.swift

@@ -3,6 +3,7 @@ import XCTest
 import WebKit
 @testable import Strada
 
+@MainActor
 class BridgeDelegateTests: XCTestCase {
     private var delegate: BridgeDelegate!
     private var destination: AppBridgeDestination!
@@ -23,8 +24,11 @@ class BridgeDelegateTests: XCTestCase {
     }
 
     func testBridgeDidInitialize() async throws {
-        try await delegate.bridgeDidInitialize()
-
+        await withCheckedContinuation { continuation in
+            bridge.registerComponentsContinuation = continuation
+            delegate.bridgeDidInitialize()
+        }
+
         XCTAssertTrue(bridge.registerComponentsWasCalled)
         XCTAssertEqual(bridge.registerComponentsArg, ["one", "two"])
 

Tests/BridgeTests.swift

@@ -2,6 +2,7 @@ import XCTest
 import WebKit
 @testable import Strada
 
+@MainActor
 class BridgeTests: XCTestCase {
     func testInitWithANewWebViewAutomaticallyLoadsIntoWebView() {
         let webView = WKWebView()
@@ -27,7 +28,6 @@ class BridgeTests: XCTestCase {
     /// NOTE: Each call to `webView.evaluateJavaScript(String)` will throw an error.
     /// We intentionally disregard any thrown errors (`try? await bridge...`)
     /// because we validate the evaluated JavaScript string ourselves.
-    @MainActor
     func testRegisterComponentCallsJavaScriptFunction() async throws {
         let webView = TestWebView()
         let bridge = Bridge(webView: webView)
@@ -37,7 +37,6 @@ class BridgeTests: XCTestCase {
         XCTAssertEqual(webView.lastEvaluatedJavaScript, "window.nativeBridge.register(\"test\")")
     }
 
-    @MainActor
     func testRegisterComponentsCallsJavaScriptFunction() async throws {
         let webView = TestWebView()
         let bridge = Bridge(webView: webView)
@@ -47,7 +46,6 @@ class BridgeTests: XCTestCase {
         XCTAssertEqual(webView.lastEvaluatedJavaScript, "window.nativeBridge.register([\"one\",\"two\"])")
     }
 
-    @MainActor
     func testUnregisterComponentCallsJavaScriptFunction() async throws {
         let webView = TestWebView()
         let bridge = Bridge(webView: webView)
@@ -57,7 +55,6 @@ class BridgeTests: XCTestCase {
         XCTAssertEqual(webView.lastEvaluatedJavaScript, "window.nativeBridge.unregister(\"test\")")
     }
 
-    @MainActor
     func testSendCallsJavaScriptFunction() async throws {
         let webView = TestWebView()
         let bridge = Bridge(webView: webView)
@@ -78,7 +75,6 @@ class BridgeTests: XCTestCase {
         XCTAssertEqual(webView.lastEvaluatedJavaScript, "window.nativeBridge.replyWith({\"component\":\"page\",\"event\":\"connect\",\"data\":{\"title\":\"Page-title\"},\"id\":\"1\"})")
     }
 
-    @MainActor
     func testEvaluateJavaScript() async throws {
         let webView = TestWebView()
         let bridge = Bridge(webView: webView)
@@ -88,7 +84,6 @@ class BridgeTests: XCTestCase {
         XCTAssertEqual(webView.lastEvaluatedJavaScript, "test(1,2,3)")
     }
 
-    @MainActor
     func testEvaluateJavaScriptReturnsErrorForNoWebView() async throws {
         let bridge = Bridge(webView: WKWebView())
         bridge.webView = nil
@@ -101,7 +96,6 @@ class BridgeTests: XCTestCase {
         XCTAssertEqual(bridgeError, BridgeError.missingWebView)
     }
 
-    @MainActor
     func testEvaluateFunction() async throws {
         let webView = TestWebView()
         let bridge = Bridge(webView: webView)

Tests/ComponentTestExample/ComposerComponentTests.swift

@@ -2,6 +2,7 @@ import XCTest
 import WebKit
 import Strada
 
+@MainActor
 final class ComposerComponentTests: XCTestCase {
     private var delegate: BridgeDelegateSpy!
     private var destination: AppBridgeDestination!

Tests/Extensions/TimeInterval+ExpectationTimeout.swift

@@ -0,0 +1,5 @@
+import Foundation
+
+extension TimeInterval {
+    static let expectationTimeout: TimeInterval = 5
+}