Fix WKNavigationDelegate policy signatures (#320)

Assisted-By: devx/058cd5b9-f1cc-431b-b520-15657ace50f1

Author: kieran-osgood-shopify

platforms/swift/Sources/ShopifyCheckoutKit/CheckoutWebView.swift

@@ -479,7 +479,7 @@ extension CheckoutWebView: WKScriptMessageHandler {
 }
 
 extension CheckoutWebView: WKNavigationDelegate {
-    func webView(_: WKWebView, decidePolicyFor action: WKNavigationAction, decisionHandler: @escaping (WKNavigationActionPolicy) -> Void) {
+    func webView(_: WKWebView, decidePolicyFor action: WKNavigationAction, decisionHandler: @escaping @MainActor @Sendable (WKNavigationActionPolicy) -> Void) {
         // Handle rare cases where the url is nil
         guard let url = action.request.url else {
             decisionHandler(.allow)
@@ -505,7 +505,7 @@ extension CheckoutWebView: WKNavigationDelegate {
         decisionHandler(.allow)
     }
 
-    func webView(_: WKWebView, decidePolicyFor navigationResponse: WKNavigationResponse, decisionHandler: @escaping (WKNavigationResponsePolicy) -> Void) {
+    func webView(_: WKWebView, decidePolicyFor navigationResponse: WKNavigationResponse, decisionHandler: @escaping @MainActor @Sendable (WKNavigationResponsePolicy) -> Void) {
         if let response = navigationResponse.response as? HTTPURLResponse {
             decisionHandler(handleResponse(response))
             return

platforms/swift/Tests/ShopifyCheckoutKitTests/CheckoutWebViewTests.swift

@@ -32,6 +32,14 @@ class CheckoutWebViewTests: XCTestCase {
         XCTAssertTrue(view.configuration.allowsInlineMediaPlayback)
     }
 
+    func testImplementsWKNavigationDelegatePolicySelectors() {
+        let navigationActionSelector = NSSelectorFromString("webView:decidePolicyForNavigationAction:decisionHandler:")
+        let navigationResponseSelector = NSSelectorFromString("webView:decidePolicyForNavigationResponse:decisionHandler:")
+
+        XCTAssertTrue(view.responds(to: navigationActionSelector))
+        XCTAssertTrue(view.responds(to: navigationResponseSelector))
+    }
+
     func testDetachBridgeIsIdempotent() {
         XCTAssertTrue(view.isBridgeAttached)