Add FC Lite killswitch and priority override

Author: mats-stripe

Diff for: Example/FinancialConnections Example/FinancialConnections Example/Playground/PlaygroundViewModel.swift

@@ -288,9 +288,12 @@ final class PlaygroundViewModel: ObservableObject {
     }
 
     func didSelectShow() {
+        let useFCLite = playgroundConfiguration.sdkType == .fcLite
+        FinancialConnectionsSDKAvailability.shouldPreferFCLite = useFCLite
+
         switch playgroundConfiguration.integrationType {
         case .standalone:
-            if playgroundConfiguration.sdkType == .fcLite {
+            if useFCLite {
                 setupFcLite()
             } else {
                 setupStandalone()

Diff for: StripePaymentSheet/StripePaymentSheet/Source/PaymentSheet/PaymentSheetLoader.swift

@@ -110,6 +110,10 @@ final class PaymentSheetLoader {
                 let isLinkEnabled = PaymentSheet.isLinkEnabled(elementsSession: elementsSession, configuration: configuration)
                 let isApplePayEnabled = PaymentSheet.isApplePayEnabled(elementsSession: elementsSession, configuration: configuration)
 
+                // Disable FC Lite if killswitch is enabled
+                let isFcLiteKillswitchEnabled = elementsSession.flags["elements_disable_fc_lite"] == true
+                FinancialConnectionsSDKAvailability.fcLiteKillswitchEnabled = isFcLiteKillswitchEnabled
+
                 // Send load finished analytic
                 // This is hacky; the logic to determine the default selected payment method belongs to the SavedPaymentOptionsViewController. We invoke it here just to report it to analytics before that VC loads.
                 let (defaultSelectedIndex, paymentOptionsViewModels) = SavedPaymentOptionsViewController.makeViewModels(

Diff for: StripePayments/StripePayments/Source/Internal/Helpers/ConnectionsSDKAvailability.swift

@@ -15,10 +15,20 @@ import UIKit
         NSClassFromString("StripeFinancialConnections.FinancialConnectionsSDKImplementation")
         as? FinancialConnectionsSDKInterface.Type
 
-    static let FinancialConnectionsLiteClass: FinancialConnectionsSDKInterface.Type? =
+    static let FinancialConnectionsLiteImplementation: FinancialConnectionsSDKInterface.Type? =
         NSClassFromString("StripePaymentSheet.FCLiteImplementation")
         as? FinancialConnectionsSDKInterface.Type
 
+    @_spi(STP) public static var fcLiteKillswitchEnabled: Bool = false
+    @_spi(STP) public static var shouldPreferFCLite: Bool = false
+
+    private static var FCLiteClassIfEnabled: FinancialConnectionsSDKInterface.Type? {
+        guard !Self.fcLiteKillswitchEnabled else {
+            return nil
+        }
+        return Self.FinancialConnectionsLiteImplementation
+    }
+
     static let isUnitTest: Bool = {
         #if targetEnvironment(simulator)
         return NSClassFromString("XCTest") != nil
@@ -37,14 +47,15 @@ import UIKit
 
     // Return true for unit tests, the value of `FinancialConnectionsSDKAvailable` for UI tests,
     // and whether or not the Financial Connections SDK is available otherwise.
+    // Falls back on FC Lite availability.
     @_spi(STP) public static var isFinancialConnectionsSDKAvailable: Bool {
         if isUnitTest {
             return true
         } else if isUITest {
             let financialConnectionsSDKAvailable = ProcessInfo.processInfo.environment["FinancialConnectionsSDKAvailable"] == "true"
             return financialConnectionsSDKAvailable
         } else {
-            return (FinancialConnectionsSDKClass != nil || FinancialConnectionsLiteClass != nil)
+            return (FinancialConnectionsSDKClass != nil || FCLiteClassIfEnabled != nil)
         }
     }
 
@@ -54,7 +65,11 @@ import UIKit
             return StubbedConnectionsSDKInterface()
         }
 
-        guard let klass = /*FinancialConnectionsSDKClass ??*/ FinancialConnectionsLiteClass else {
+        let klass: FinancialConnectionsSDKInterface.Type? = shouldPreferFCLite
+            ? (FCLiteClassIfEnabled ?? FinancialConnectionsSDKClass)
+            : (FinancialConnectionsSDKClass ?? FCLiteClassIfEnabled)
+
+        guard let klass else {
             return nil
         }