Swift/Kotlin alignment: discard preload cache on configuration changes

platforms/android/README.md

@@ -258,6 +258,11 @@ Clear unused preloaded checkout work with `invalidate`:
 ShopifyCheckoutKit.invalidate()
 ```
 
+Updating configuration through `ShopifyCheckoutKit.configure {}` triggers
+`ShopifyCheckoutKit.invalidate()`. Discarding cached preloads avoids presenting a
+stale checkout. If a preload may already have run when configuration changes,
+call `preload` again.
+
 Preloading is enabled by default. Disable it when appropriate, for example for data-saver modes or app-specific runtime conditions:
 
 ```kotlin

platforms/android/lib/src/main/java/com/shopify/checkoutkit/ShopifyCheckoutKit.kt

@@ -35,6 +35,8 @@ public object ShopifyCheckoutKit {
     /**
      * Allows configuring ShopifyCheckoutKit.
      *
+     * Calling this function invalidates any cached preload.
+     *
      * Kotlin example:
      * {@code ShopifyCheckoutKit.configure { it.appearance = CheckoutAppearance.App(ColorScheme.Dark()) }}
      *

platforms/react-native/README.md

@@ -767,7 +767,15 @@ Instead, a better approach is to call `preload()` when you have a strong enough
 
 ### Cache invalidation
 
-Should you wish to manually clear the preload cache, call `invalidate()` on your `ShopifyCheckout` instance or the value returned by `useShopifyCheckout()`.
+To manually clear the preload cache, call `invalidate()` on your `ShopifyCheckout`
+instance or the value returned by `useShopifyCheckout()`.
+
+Updating configuration through `shopifyCheckout.setConfig(...)` or the
+`configuration` prop on `ShopifyCheckoutProvider` triggers
+`shopifyCheckout.invalidate()`. Discarding cached preloads avoids presenting a
+stale checkout. If a preload may already have run when configuration changes,
+call `preload` again. Keep a provider's configuration object stable across renders to
+avoid unintentionally invalidating preloads.
 
 ## Checkout lifecycle
 

platforms/swift/README.md

@@ -226,6 +226,12 @@ Clear unused preloaded checkout work with `invalidate`:
 ShopifyCheckoutKit.invalidate()
 ```
 
+Updating configuration through `ShopifyCheckoutKit.configure {}` or a direct
+mutation such as `ShopifyCheckoutKit.configuration.title = "Checkout"` triggers
+`ShopifyCheckoutKit.invalidate()`. Discarding cached preloads avoids presenting a
+stale checkout. If a preload may already have run when configuration changes,
+call `preload` again.
+
 Preloading is enabled by default. Disable it when appropriate, for example for data-saver modes or app-specific runtime conditions:
 
 ```swift

platforms/swift/Sources/ShopifyCheckoutKit/ShopifyCheckoutKit.swift

@@ -9,35 +9,29 @@ public let version = "4.0.0-alpha.5"
 private let lockedCheckoutKitConfiguration = LockedValue(Configuration())
 
 /// The configuration options for the `ShopifyCheckoutKit` library.
+///
+/// Assigning configuration invalidates any cached preload.
 public var configuration: Configuration {
     get { lockedCheckoutKitConfiguration.get() }
     set {
-        let previousConfiguration = lockedCheckoutKitConfiguration.get()
         lockedCheckoutKitConfiguration.set(newValue)
-        applyConfigurationChange(
-            configuration: newValue,
-            previousConfiguration: previousConfiguration
-        )
+        applyConfigurationChange(newValue)
     }
 }
 
-/// A convienence function for configuring the `ShopifyCheckoutKit` library.
+/// A convenience function for configuring the `ShopifyCheckoutKit` library.
+///
+/// Calling this function invalidates any cached preload.
 public func configure(_ block: (inout Configuration) -> Void) {
-    let previousConfiguration = lockedCheckoutKitConfiguration.get()
     lockedCheckoutKitConfiguration.update(block)
-    applyConfigurationChange(
-        configuration: lockedCheckoutKitConfiguration.get(),
-        previousConfiguration: previousConfiguration
-    )
+    applyConfigurationChange(lockedCheckoutKitConfiguration.get())
 }
 
-private func applyConfigurationChange(configuration: Configuration, previousConfiguration: Configuration) {
+private func applyConfigurationChange(_ configuration: Configuration) {
     OSLogger.shared.logLevel = configuration.logLevel
 
-    if configuration.preloading.enabled != previousConfiguration.preloading.enabled {
-        Task { @MainActor in
-            invalidate()
-        }
+    Task { @MainActor in
+        invalidate()
     }
 }
 

platforms/swift/Tests/ShopifyCheckoutKitTests/ConfigurationTests.swift

@@ -69,21 +69,22 @@ class ConfigurationTests: XCTestCase {
         XCTAssertFalse(CheckoutWebView.preloadCache.hasEntry())
     }
 
-    func testChangingConfigurationWithoutChangingPreloadingDoesNotInvalidatePreload() async throws {
+    func testChangingConfigurationWithoutChangingPreloadingInvalidatesPreload() async throws {
         let checkoutURL = try XCTUnwrap(URL(string: "https://shopify1.shopify.com/checkouts/cn/123"))
 
+        await Task.yield()
         ShopifyCheckoutKit.preload(checkout: checkoutURL)
         XCTAssertTrue(CheckoutWebView.preloadCache.hasEntry())
 
         ShopifyCheckoutKit.configure {
             $0.title = "Thank you!"
         }
 
-        for _ in 0 ..< 10 {
+        for _ in 0 ..< 10 where CheckoutWebView.preloadCache.hasEntry() {
             await Task.yield()
         }
 
-        XCTAssertTrue(CheckoutWebView.preloadCache.hasEntry())
+        XCTAssertFalse(CheckoutWebView.preloadCache.hasEntry())
     }
 
     func testAppearanceCanBeSetDirectly() {