Read the default_payment_method field from elements session and use that as the default PM

StripePaymentSheet/StripePaymentSheet/Source/Internal/API Bindings/v1-elements-sessions/ElementsCustomer.swift

@@ -36,14 +36,17 @@ struct ElementsCustomer: Equatable, Hashable {
         }
 
         // Optional
-        // to test default payment methods reading from back end, hard-code a valid default payment method
-        // later, when API calls to get and update default payment method are available, that will no longer be needed
         let defaultPaymentMethod = response["default_payment_method"] as? String
         return ElementsCustomer(paymentMethods: paymentMethods, defaultPaymentMethod: defaultPaymentMethod, customerSession: customerSession)
     }
 
-    static func getDefaultPaymentMethod(from customer: ElementsCustomer?) -> STPPaymentMethod? {
-        guard let customer = customer else { return nil }
-        return customer.paymentMethods.first { $0.stripeId == customer.defaultPaymentMethod }
+    func getDefaultOrFirstPaymentMethod() -> STPPaymentMethod? {
+        // if customer has a default payment method from the elements session, return the default payment method
+        let defaultSavedPaymentMethod = paymentMethods.first { $0.stripeId == defaultPaymentMethod }
+        if let defaultSavedPaymentMethod = defaultSavedPaymentMethod {
+            return defaultSavedPaymentMethod
+        }
+        // otherwise, return the first payment method from the customer's list of saved payment methods
+        return paymentMethods.first
     }
 }

StripePaymentSheet/StripePaymentSheet/Source/PaymentSheet/CustomerSessionAdapter/CustomerSessionAdapter.swift

@@ -108,13 +108,14 @@ extension CustomerSessionAdapter {
     }
 
     func fetchSelectedPaymentOption(for customerId: String, customer: ElementsCustomer? = nil) -> CustomerPaymentOption? {
-        guard configuration.allowsSetAsDefaultPM,
-              let customer = customer,
-              let defaultPaymentMethod = customer.defaultPaymentMethod else {
-            return CustomerPaymentOption.defaultPaymentMethod(for: customerId)
+        // if opted in to the "set as default" feature, try to get default payment method from elements session
+        if configuration.allowsSetAsDefaultPM {
+            guard let customer = customer,
+                 let defaultPaymentMethod = customer.getDefaultOrFirstPaymentMethod() else { return nil }
+            return CustomerPaymentOption.stripeId(defaultPaymentMethod.stripeId)
         }
 
-        return CustomerPaymentOption.stripeId(defaultPaymentMethod)
+        return CustomerPaymentOption.defaultPaymentMethod(for: customerId)
     }
 
     func detachPaymentMethod(paymentMethodId: String) async throws {

StripePaymentSheet/StripePaymentSheet/Source/PaymentSheet/CustomerSheet/CustomerSheet.swift

@@ -329,9 +329,10 @@ extension CustomerSheet {
 
             var selectedPaymentOption: CustomerPaymentOption?
 
-            // get default payment method from elements session
-            if configuration.allowsSetAsDefaultPM,
-               let defaultPaymentMethod = ElementsCustomer.getDefaultPaymentMethod(from: elementsSession.customer) {
+            // if opted in to the "set as default" feature, try to get default payment method from elements session
+            if configuration.allowsSetAsDefaultPM {
+                guard let customer = elementsSession.customer,
+                    let defaultPaymentMethod = customer.getDefaultOrFirstPaymentMethod() else { return nil }
                 selectedPaymentOption = CustomerPaymentOption.stripeId(defaultPaymentMethod.stripeId)
             }
             else {

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

@@ -37,12 +37,6 @@ extension EmbeddedPaymentElement {
             isFlatCheckmarkStyle: configuration.appearance.embeddedPaymentElement.row.style == .flatWithCheckmark
         )
         let initialSelection: EmbeddedPaymentMethodsView.Selection? = {
-            // get default payment method from elements session
-            if configuration.allowsSetAsDefaultPM,
-               let defaultPaymentMethod = ElementsCustomer.getDefaultPaymentMethod(from: loadResult.elementsSession.customer) {
-                    return .saved(paymentMethod: defaultPaymentMethod)
-            }
-
             // Select the previous payment option
             switch previousPaymentOption {
             case .applePay:
@@ -60,7 +54,19 @@ extension EmbeddedPaymentElement {
             }
 
             // If there's no previous customer input, default to the customer's default or the first saved payment method, if any
-            let customerDefault = CustomerPaymentOption.defaultPaymentMethod(for: configuration.customer?.id)
+            var customerDefault: CustomerPaymentOption?
+            // if opted in to the "set as default" feature, try to get default payment method from elements session
+            if configuration.allowsSetAsDefaultPM {
+                if let defaultPaymentMethod = loadResult.elementsSession.customer?.getDefaultOrFirstPaymentMethod() {
+                    customerDefault = CustomerPaymentOption.stripeId(defaultPaymentMethod.stripeId)
+                }
+                else {
+                    customerDefault = nil
+                }
+            }
+            else {
+                customerDefault = CustomerPaymentOption.defaultPaymentMethod(for: configuration.customer?.id)
+            }
             switch customerDefault {
             case .applePay:
                 return .applePay

StripePaymentSheet/StripePaymentSheet/Source/PaymentSheet/PaymentSheetLoader.swift

@@ -319,9 +319,10 @@ final class PaymentSheetLoader {
         // Move default PM to front
         if let customerID = configuration.customer?.id {
             var defaultPaymentMethodOption: CustomerPaymentOption?
-            // get default payment method from elements session
-            if configuration.allowsSetAsDefaultPM,
-               let defaultPaymentMethod = ElementsCustomer.getDefaultPaymentMethod(from: elementsSession.customer) {
+            // if opted in to the "set as default" feature, try to get default payment method from elements session
+            if configuration.allowsSetAsDefaultPM {
+                guard let customer = elementsSession.customer,
+                  let defaultPaymentMethod = customer.getDefaultOrFirstPaymentMethod() else { return [] }
                 defaultPaymentMethodOption = CustomerPaymentOption.stripeId(defaultPaymentMethod.stripeId)
             }
             else {

StripePaymentSheet/StripePaymentSheet/Source/PaymentSheet/Saved Payment Method Screen/SavedPaymentOptionsViewController.swift

@@ -446,10 +446,15 @@ class SavedPaymentOptionsViewController: UIViewController {
     static func makeViewModels(savedPaymentMethods: [STPPaymentMethod], customerID: String?, showApplePay: Bool, showLink: Bool, allowsSetAsDefaultPM: Bool, customer: ElementsCustomer?) -> (defaultSelectedIndex: Int, viewModels: [Selection]) {
         // Get the default
         var defaultPaymentMethodOption: CustomerPaymentOption?
-        // get default payment method from elements session
-        if allowsSetAsDefaultPM,
-           let defaultPaymentMethod = ElementsCustomer.getDefaultPaymentMethod(from: customer) {
-            defaultPaymentMethodOption = CustomerPaymentOption.stripeId(defaultPaymentMethod.stripeId)
+        // if opted in to the "set as default" feature, try to get default payment method from elements session
+        if allowsSetAsDefaultPM {
+           if let customer = customer,
+              let defaultPaymentMethod = customer.getDefaultOrFirstPaymentMethod() {
+               defaultPaymentMethodOption = CustomerPaymentOption.stripeId(defaultPaymentMethod.stripeId)
+           }
+            else {
+                defaultPaymentMethodOption = nil
+            }
         }
         else {
             defaultPaymentMethodOption = CustomerPaymentOption.defaultPaymentMethod(for: customerID)

StripePaymentSheet/StripePaymentSheet/Source/PaymentSheet/ViewControllers/PaymentSheetVerticalViewController.swift

@@ -288,11 +288,6 @@ class PaymentSheetVerticalViewController: UIViewController, FlowControllerViewCo
             if let selection {
                 return selection
             }
-            // get default payment method from elements session
-            if configuration.allowsSetAsDefaultPM,
-               let defaultPaymentMethod = ElementsCustomer.getDefaultPaymentMethod(from: elementsSession.customer) {
-                return .saved(paymentMethod: defaultPaymentMethod)
-            }
 
             switch previousPaymentOption {
             case .applePay:
@@ -323,7 +318,20 @@ class PaymentSheetVerticalViewController: UIViewController, FlowControllerViewCo
                     }
                 }
                 // Default to the customer's default or the first saved payment method, if any
-                let customerDefault = CustomerPaymentOption.defaultPaymentMethod(for: configuration.customer?.id)
+                var customerDefault: CustomerPaymentOption?
+                // if opted in to the "set as default" feature, try to get default payment method from elements session
+                if configuration.allowsSetAsDefaultPM {
+                    if let customer = elementsSession.customer,
+                       let defaultPaymentMethod = customer.getDefaultOrFirstPaymentMethod() {
+                        customerDefault = CustomerPaymentOption.stripeId(defaultPaymentMethod.stripeId)
+                    }
+                    else {
+                        customerDefault = nil
+                    }
+                }
+                else {
+                    customerDefault = CustomerPaymentOption.defaultPaymentMethod(for: configuration.customer?.id)
+                }
                 switch customerDefault {
                 case .applePay:
                     return isFlowController ? .applePay : nil // Only default to Apple Pay in flow controller mode