Implement embedded update (part 1)

.gitattributes

@@ -0,0 +1 @@
+*.tail linguist-generated=true

StripePaymentSheet/StripePaymentSheet.xcodeproj/project.pbxproj

@@ -236,6 +236,7 @@
 		B6B3481CBA798CF22EE8411A /* TextFieldElement+IBAN.swift in Sources */ = {isa = PBXBuildFile; fileRef = 570931B897DCCAC0F55FB6E3 /* TextFieldElement+IBAN.swift */; };
 		B6BF12392C2F2E790033601E /* PaymentSheetImageTests.swift in Sources */ = {isa = PBXBuildFile; fileRef = B6BF12382C2F2E780033601E /* PaymentSheetImageTests.swift */; };
 		B6CACC9E2CB8B90700682ECE /* EmbeddedPaymentElement+Internal.swift in Sources */ = {isa = PBXBuildFile; fileRef = B6CACC9D2CB8B8E800682ECE /* EmbeddedPaymentElement+Internal.swift */; };
+		B6CACCA02CBD9A3300682ECE /* EmbeddedPaymentElementTest.swift in Sources */ = {isa = PBXBuildFile; fileRef = B6CACC9F2CBD9A3300682ECE /* EmbeddedPaymentElementTest.swift */; };
 		B6D1B3662C5DFCE800A9E0D7 /* PaymentSheetAnalyticsHelperTest.swift in Sources */ = {isa = PBXBuildFile; fileRef = B6D1B3652C5DFCE800A9E0D7 /* PaymentSheetAnalyticsHelperTest.swift */; };
 		B6E8C7FB2C184A0300B977B2 /* PaymentSheetFormFactory+Mandates.swift in Sources */ = {isa = PBXBuildFile; fileRef = B6E8C7FA2C184A0300B977B2 /* PaymentSheetFormFactory+Mandates.swift */; };
 		B6F4C5F82CADB0CB00AF3767 /* USBankAccountPaymentMethodElementTest.swift in Sources */ = {isa = PBXBuildFile; fileRef = B6F4C5F72CADB0CB00AF3767 /* USBankAccountPaymentMethodElementTest.swift */; };
@@ -607,6 +608,7 @@
 		B68CB9622B0D2169006ACDB1 /* STPAPIClient+PaymentSheetTest.swift */ = {isa = PBXFileReference; fileEncoding = 4; lastKnownFileType = sourcecode.swift; path = "STPAPIClient+PaymentSheetTest.swift"; sourceTree = "<group>"; };
 		B6BF12382C2F2E780033601E /* PaymentSheetImageTests.swift */ = {isa = PBXFileReference; lastKnownFileType = sourcecode.swift; path = PaymentSheetImageTests.swift; sourceTree = "<group>"; };
 		B6CACC9D2CB8B8E800682ECE /* EmbeddedPaymentElement+Internal.swift */ = {isa = PBXFileReference; lastKnownFileType = sourcecode.swift; path = "EmbeddedPaymentElement+Internal.swift"; sourceTree = "<group>"; };
+		B6CACC9F2CBD9A3300682ECE /* EmbeddedPaymentElementTest.swift */ = {isa = PBXFileReference; lastKnownFileType = sourcecode.swift; path = EmbeddedPaymentElementTest.swift; sourceTree = "<group>"; };
 		B6D1B3652C5DFCE800A9E0D7 /* PaymentSheetAnalyticsHelperTest.swift */ = {isa = PBXFileReference; lastKnownFileType = sourcecode.swift; path = PaymentSheetAnalyticsHelperTest.swift; sourceTree = "<group>"; };
 		B6E8C7FA2C184A0300B977B2 /* PaymentSheetFormFactory+Mandates.swift */ = {isa = PBXFileReference; lastKnownFileType = sourcecode.swift; path = "PaymentSheetFormFactory+Mandates.swift"; sourceTree = "<group>"; };
 		B6F4C5F72CADB0CB00AF3767 /* USBankAccountPaymentMethodElementTest.swift */ = {isa = PBXFileReference; lastKnownFileType = sourcecode.swift; path = USBankAccountPaymentMethodElementTest.swift; sourceTree = "<group>"; };
@@ -1425,11 +1427,12 @@
 				989C2E3E03E42DA64A2FAE0D /* CustomerSheetSnapshotTests.swift */,
 				31699A822BE183D40048677F /* DownloadManagerTest.swift */,
 				73FB30705EC36BD0868904A2 /* Elements+TestHelpers.swift */,
+				B6CACC9F2CBD9A3300682ECE /* EmbeddedPaymentElementTest.swift */,
 				61FB6BCC2C8901B200F8E074 /* EmbeddedPaymentMethodsViewSnapshotTests.swift */,
 				614068E12CB0BF10003D2F12 /* EmbeddedPaymentMethodsViewTests.swift */,
 				64C8F350CDB5A29F62E86592 /* FlowControllerStateTests.swift */,
-				6B0E5AE62C08F4B5008AAFBE /* IntentConfirmParamsTest.swift */,
 				61D842902CB06047009D2D51 /* FormMandateProviderTests.swift */,
+				6B0E5AE62C08F4B5008AAFBE /* IntentConfirmParamsTest.swift */,
 				990304EF35A0EE37DCE20D5B /* IntentStatusPollerTest.swift */,
 				FCA28FF8CD5BA829A44CDCE7 /* Link */,
 				33B8F21A22FA091BC9D2924B /* LinkStubs.swift */,
@@ -1719,6 +1722,7 @@
 				9C42A106FF30A22CFBB38AE8 /* Elements+TestHelpers.swift in Sources */,
 				D442C49095DDEC2C6ADAF392 /* FlowControllerStateTests.swift in Sources */,
 				619AF0852BF56C5E00D1C981 /* PaymentMethodRowButtonSnapshotTests.swift in Sources */,
+				B6CACCA02CBD9A3300682ECE /* EmbeddedPaymentElementTest.swift in Sources */,
 				2EC9C94DD8D62E4F4EFC8AB8 /* IntentStatusPollerTest.swift in Sources */,
 				ABC3A7CF6D5B21D0C9684A09 /* LinkPopupURLParserTests.swift in Sources */,
 				F94F6A157CEB937896B682D4 /* LinkURLGeneratorTests.swift in Sources */,

StripePaymentSheet/StripePaymentSheet/Source/PaymentSheet/Embedded/EmbeddedPaymentElement+Internal.swift

@@ -9,7 +9,8 @@ extension EmbeddedPaymentElement {
     @MainActor
     static func makeView(
         configuration: Configuration,
-        loadResult: PaymentSheetLoader.LoadResult
+        loadResult: PaymentSheetLoader.LoadResult,
+        delegate: EmbeddedPaymentMethodsViewDelegate? = nil
     ) -> EmbeddedPaymentMethodsView {
         let shouldShowApplePay = PaymentSheet.isApplePayEnabled(elementsSession: loadResult.elementsSession, configuration: configuration)
         let shouldShowLink = PaymentSheet.isLinkEnabled(elementsSession: loadResult.elementsSession, configuration: configuration)
@@ -46,7 +47,8 @@ extension EmbeddedPaymentElement {
             shouldShowLink: shouldShowLink,
             savedPaymentMethodAccessoryType: savedPaymentMethodAccessoryType,
             mandateProvider: mandateProvider,
-            shouldShowMandate: configuration.embeddedViewDisplaysMandateText
+            shouldShowMandate: configuration.embeddedViewDisplaysMandateText,
+            delegate: delegate
         )
     }
 }

StripePaymentSheet/StripePaymentSheet/Source/PaymentSheet/Embedded/EmbeddedPaymentElement.swift

@@ -13,10 +13,11 @@ import UIKit
 /// An object that manages a view that displays payment methods and completes a checkout.
 @_spi(EmbeddedPaymentElementPrivateBeta)
 @MainActor
-public class EmbeddedPaymentElement {
+public final class EmbeddedPaymentElement {
 
     /// A view that displays payment methods. It can present a sheet to collect more details or display saved payment methods.
     public var view: UIView {
+        // TODO: Make this a _container view_ so that we can swap out the inner `embeddedPaymentMethodsView` when `update` is called.
         return embeddedPaymentMethodsView
     }
 
@@ -29,7 +30,8 @@ public class EmbeddedPaymentElement {
     /// See `EmbeddedPaymentElementDelegate`.
     public weak var delegate: EmbeddedPaymentElementDelegate?
 
-    public struct PaymentOptionDisplayData {
+    /// Contains details about a payment method that can be displayed to the customer
+    public struct PaymentOptionDisplayData: Equatable {
         /// An image representing a payment method; e.g. the Apple Pay logo or a VISA logo
         public let image: UIImage
         /// A user facing string representing the payment method; e.g. "Apple Pay" or "····4242" for a card
@@ -90,13 +92,65 @@ public class EmbeddedPaymentElement {
     /// Call this method when the IntentConfiguration values you used to initialize `EmbeddedPaymentElement` (amount, currency, etc.) change.
     /// This ensures the appropriate payment methods are displayed, collect the right fields, etc.
     /// - Parameter intentConfiguration: An updated IntentConfiguration.
-    /// - Returns: The result of the update. Any calls made to `update` before this call that are still in progress will return a `.canceled` result.
+    /// - Returns: The result of the update.
     /// - Note: Upon completion, `paymentOption` may become nil if it's no longer available.
+    /// - Note: If you call `update` while a previous call to `update` is still in progress, the previous call returns `.canceled`.
     public func update(
         intentConfiguration: IntentConfiguration
     ) async -> UpdateResult {
-        // TODO(https://jira.corp.stripe.com/browse/MOBILESDK-2524)
-        return .succeeded
+        // Cancel the old task and let it finish so that merchants receive update results in order
+        currentUpdateTask?.cancel()
+        _ = await currentUpdateTask?.value
+        // Start the new update task
+        let currentUpdateTask = Task { [weak self, configuration, paymentOption] in
+            // 1. Reload v1/elements/session.
+            let loadResult: PaymentSheetLoader.LoadResult
+            do {
+                // TODO: Change dummy analytics helper
+                let dummyAnalyticsHelper = PaymentSheetAnalyticsHelper(isCustom: false, configuration: .init())
+                // TODO(nice to have): Make `load` respect task cancellation to reduce network consumption
+                loadResult = try await PaymentSheetLoader.load(
+                    mode: .deferredIntent(intentConfiguration),
+                    configuration: configuration,
+                    analyticsHelper: dummyAnalyticsHelper,
+                    integrationShape: .embedded
+                )
+            } catch {
+                return UpdateResult.failed(error: error)
+            }
+            guard !Task.isCancelled else {
+                return UpdateResult.canceled
+            }
+
+            // 2. Re-initialize embedded view to update the UI to match the newly loaded data.
+            let embeddedPaymentMethodsView = Self.makeView(
+                configuration: configuration,
+                loadResult: loadResult,
+                delegate: self
+                // TODO: https://jira.corp.stripe.com/browse/MOBILESDK-2583 Restore previous payment option
+            )
+
+            // 2. Pre-load image into cache
+            // Hack: Accessing paymentOption has the side-effect of ensuring its `image` property is loaded (from the internet instead of disk) before we call the completion handler.
+            // Call this on a detached Task b/c this synchronously (!) loads the image from network and we don't want to block the main actor
+            let fetchPaymentOption = Task.detached(priority: .userInitiated) {
+                return await embeddedPaymentMethodsView.displayData
+            }
+            _ = await fetchPaymentOption.value
+
+            guard let self, !Task.isCancelled else {
+                return .canceled
+            }
+            // At this point, we're the latest update - update self properties and inform our delegate.
+            self.loadResult = loadResult
+            self.embeddedPaymentMethodsView = embeddedPaymentMethodsView
+            if paymentOption != embeddedPaymentMethodsView.displayData {
+                self.delegate?.embeddedPaymentElementDidUpdatePaymentOption(embeddedPaymentElement: self)
+            }
+            return .succeeded
+        }
+        self.currentUpdateTask = currentUpdateTask
+        return await currentUpdateTask.value
     }
 
     /// Completes the payment or setup.
@@ -109,18 +163,16 @@ public class EmbeddedPaymentElement {
 
     // MARK: - Internal
 
-    private let embeddedPaymentMethodsView: EmbeddedPaymentMethodsView
-
-    private let loadResult: PaymentSheetLoader.LoadResult
+    internal private(set) var embeddedPaymentMethodsView: EmbeddedPaymentMethodsView
+    internal private(set) var loadResult: PaymentSheetLoader.LoadResult
+    internal private(set) var currentUpdateTask: Task<UpdateResult, Never>?
 
     private init(
         configuration: Configuration,
-        loadResult: PaymentSheetLoader.LoadResult,
-        delegate: EmbeddedPaymentElementDelegate? = nil
+        loadResult: PaymentSheetLoader.LoadResult
     ) {
         self.configuration = configuration
         self.loadResult = loadResult
-        self.delegate = delegate
         self.embeddedPaymentMethodsView = Self.makeView(
             configuration: configuration,
             loadResult: loadResult

StripePaymentSheet/StripePaymentSheet/Source/PaymentSheet/Embedded/EmbeddedPaymentMethodsView.swift

@@ -49,19 +49,23 @@ class EmbeddedPaymentMethodsView: UIView {
 
     weak var delegate: EmbeddedPaymentMethodsViewDelegate?
 
-    init(initialSelection: Selection?,
-         paymentMethodTypes: [PaymentSheet.PaymentMethodType],
-         savedPaymentMethod: STPPaymentMethod?,
-         appearance: PaymentSheet.Appearance,
-         shouldShowApplePay: Bool,
-         shouldShowLink: Bool,
-         savedPaymentMethodAccessoryType: RowButton.RightAccessoryButton.AccessoryType?,
-         mandateProvider: MandateTextProvider,
-         shouldShowMandate: Bool = true) {
+    init(
+        initialSelection: Selection?,
+        paymentMethodTypes: [PaymentSheet.PaymentMethodType],
+        savedPaymentMethod: STPPaymentMethod?,
+        appearance: PaymentSheet.Appearance,
+        shouldShowApplePay: Bool,
+        shouldShowLink: Bool,
+        savedPaymentMethodAccessoryType: RowButton.RightAccessoryButton.AccessoryType?,
+        mandateProvider: MandateTextProvider,
+        shouldShowMandate: Bool = true,
+        delegate: EmbeddedPaymentMethodsViewDelegate? = nil
+    ) {
         self.appearance = appearance
         self.selection = initialSelection
         self.mandateProvider = mandateProvider
         self.shouldShowMandate = shouldShowMandate
+        self.delegate = delegate
         super.init(frame: .zero)
 
         let rowButtonAppearance = appearance.embeddedPaymentElement.style.appearanceForStyle(appearance: appearance)

StripePaymentSheet/StripePaymentSheet/Source/PaymentSheet/Embedded/UIStackView+Separator.swift

@@ -11,8 +11,10 @@ extension UIStackView {
     func addSeparators(color: UIColor, backgroundColor: UIColor, thickness: CGFloat = 1, inset: UIEdgeInsets, addTopSeparator: Bool = true, addBottomSeparator: Bool = true) {
         let numberOfSeparators = arrangedSubviews.count - 1
 
-        for i in 1...numberOfSeparators {
-            addSeparator(color: color, backgroundColor: backgroundColor, thickness: thickness, inset: inset, at: i * 2 - 1)
+        if numberOfSeparators > 0 {
+            for i in 1...numberOfSeparators {
+                addSeparator(color: color, backgroundColor: backgroundColor, thickness: thickness, inset: inset, at: i * 2 - 1)
+            }
         }
 
         if addTopSeparator {

StripePaymentSheet/StripePaymentSheet/Source/PaymentSheet/PaymentSheetLoader.swift

@@ -228,7 +228,12 @@ final class PaymentSheetLoader {
     static func fetchElementsSessionAndIntent(mode: PaymentSheet.InitializationMode, configuration: PaymentElementConfiguration, analyticsHelper: PaymentSheetAnalyticsHelper) async throws -> ElementSessionAndIntent {
         let intent: Intent
         let elementsSession: STPElementsSession
-        let clientDefaultPaymentMethod = defaultStripePaymentMethodId(forCustomerID: configuration.customer?.id)
+        let clientDefaultPaymentMethod: String? = {
+            guard let customer = configuration.customer else {
+                return nil
+            }
+            return defaultStripePaymentMethodId(forCustomerID: customer.id)
+        }()
 
         switch mode {
         case .paymentIntentClientSecret(let clientSecret):