[Swift] 4.0.0-alpha.4

Breaking changes

New checkout failure case

Checkout now reports WebKit content-process termination as a terminal failure through checkoutDidFail(error:) or .onFail.

CheckoutErrorCode includes a new case. Exhaustive switches must handle it:

 switch error.code {
 case .networkError:
     showRetry()
+case .webContentProcessTerminated:
+    showRetry()
 case .sdkError:
     showBrowserFallback()
 // Other cases...
 }

Checkout Kit does not automatically reload after the process terminates. The buyer must explicitly retry or reopen checkout.

New preload failure case

PreloadState.FailureReason also includes a new case. Exhaustive switches over preload failures must be updated:

 switch reason {
 case .httpError(let statusCode):
     recordHTTPFailure(statusCode)
 case .navigationFailed:
     recordNavigationFailure()
-case .keepAliveLost, .protocolError:
+case .keepAliveLost, .webContentProcessTerminated, .protocolError:
     discardPreload()
 }

A terminated background WebView now transitions the preload to:

.failed(reason: .webContentProcessTerminated)

This failure applies only to the preload. A subsequent checkout presentation can still load normally.

Additive changes

Incoming message origin validation

Checkout messages can now be restricted to explicitly trusted origins using allowedMessageOrigins:

 ShopifyCheckoutKit.configure {
+    $0.allowedMessageOrigins = [
+        "https://checkout.example.com",
+        "https://*.example.com"
+    ]
 }

The loaded checkout origin and shop.app are always trusted. An empty list preserves the previous behavior and accepts messages from all origins.

Rejected messages can be observed with onMessageRejected:

 ShopifyCheckoutKit.configure {
+    $0.onMessageRejected = { rejection in
+        logger.warning(
+            "Rejected message from \(rejection.origin): \(rejection.reason)"
+        )
+    }
 }

The MessageRejection payload is untrusted and should only be used for diagnostics.

Enumerate checkout error codes

CheckoutErrorCode now conforms to CaseIterable:

-public enum CheckoutErrorCode: String, Codable, Sendable {
+public enum CheckoutErrorCode: String, Codable, CaseIterable, Sendable {

This allows applications and tests to enumerate every known error code:

for code in CheckoutErrorCode.allCases {
    registerAnalyticsValue(code.rawValue)
}

Behavior changes

WebKit content-process termination no longer fails silently

When WebKit terminates an active checkout's content process, Checkout Kit now reports .webContentProcessTerminated.

For a background preload, Checkout Kit evicts the cached WebView and reports:

.failed(reason: .webContentProcessTerminated)

Checkout header layout changed

The checkout navigation bar now uses a transparent background, and checkout content extends behind the navigation bar:

-checkoutView.scrollView.contentInsetAdjustmentBehavior = .never
+checkoutView.scrollView.contentInsetAdjustmentBehavior = .automatic

-checkoutView.topAnchor.constraint(
-    equalTo: view.safeAreaLayoutGuide.topAnchor
-)
+checkoutView.topAnchor.constraint(
+    equalTo: view.topAnchor
+)

Apps that visually test or customize checkout presentation should verify their header, title, close button, and content positioning after upgrading.

What's Changed

• add multipass deprecation warning by @kiftio in #564
• Document checkout lifecycle errors by @kiftio in #538
• Handle WebView process termination by @kiftio in #539
• feat: incoming message origin validation for ios by @michaeljsXu in #476
• ci: cache Mint packages in the Swift test workflow by @kieran-osgood-shopify in #586
• [Swift]: conform CheckoutErrorCode to CaseIterable by @kieran-osgood-shopify in #571
• ci: extract Mint provisioning into a setup-mint composite action by @kieran-osgood-shopify in #591
• Readme discrepancies by @markmur in #526
• Add sample app test seams and run them in CI by @kieran-osgood-shopify in #553
• [Swift] Drop header background, anchor webview to top by @markmur in #615
• feat: setup nightly for testflight swift by @kieran-osgood-shopify in #605
• Release Swift 4.0.0-alpha.4 by @tiagocandido in #622

Full Changelog: 4.0.0-alpha.3...4.0.0-alpha.4