[BANKCON-14524] Allow pay by bank when linkCardBrand criteria is met …

…& dedupe instant debits (#4021)

## Summary

Per the [Panther project
plan](https://docs.google.com/document/d/1ErJVA3lLvNspPe3A8uYP9feK8Yvfq-Sw5aatNIvlGxk/edit?usp=sharing),
this adds Link Card Brand as a payment method when the following
criteria is met:

- `link_funding_sources` contains `BANK_ACCOUNT`
- `US_BANK_ACCOUNT` is not an available payment method.
- `link_mode` is `LINK_CARD_BRAND`

This also makes sure that both Instant Debits and Link Card Brand won't
both be shown at the same time, since they appear as identical payment
methods to a user (same name, icon, and elements form).

## Motivation

Building Panther support!

## Testing

Added a unit test, and manually verified the new payment method shows up
when the conditions are met:


https://github.com/user-attachments/assets/28a1f8d6-abab-4143-ae1f-0a468340718d


## Changelog

N/a

Example/PaymentSheet Example/PaymentSheetUITest/PaymentSheetUITest.swift

@@ -196,7 +196,7 @@ class PaymentSheetStandardUITests: PaymentSheetUITestCase {
         // `mc_load_succeeded` event `selected_lpm` should be "apple_pay", the default payment method.
         XCTAssertEqual(analyticsLog[2][string: "selected_lpm"], "apple_pay")
         app.buttons["+ Add"].waitForExistenceAndTap()
-        XCTAssertTrue(app.staticTexts["Add a card"].waitForExistence(timeout: 2))
+        XCTAssertTrue(app.staticTexts["Card information"].waitForExistence(timeout: 2))
 
         // Should fire the `mc_form_shown` event w/ `selected_lpm` = card
         XCTAssertEqual(analyticsLog.last?[string: "event"], "mc_form_shown")

StripePaymentSheet/StripePaymentSheet/Source/PaymentSheet/PaymentMethodType.swift

@@ -165,12 +165,29 @@ extension PaymentSheet {
                 // External Payment Methods
                 + elementsSession.externalPaymentMethods.map { PaymentMethodType.external($0) }
 
-            if
-                elementsSession.orderedPaymentMethodTypes.contains(.link),
-                !elementsSession.orderedPaymentMethodTypes.contains(.USBankAccount),
-                !intent.isDeferredIntent,
+            // We should manually add Instant Debits as a payment method when:
+            // - Link is an available payment method.
+            // - US Bank Account is *not* an available payment method.
+            // - Not a deferred intent flow.
+            // - Link Funding Sources contains Bank Account.
+            var eligibleForInstantDebits: Bool {
+                elementsSession.orderedPaymentMethodTypes.contains(.link) &&
+                !elementsSession.orderedPaymentMethodTypes.contains(.USBankAccount) &&
+                !intent.isDeferredIntent &&
                 elementsSession.linkFundingSources?.contains(.bankAccount) == true
-            {
+            }
+
+            // We should manually add Link Card Brand as a payment method when:
+            // - Link Funding Sources contains Bank Account.
+            // - US Bank Account is *not* an available payment method.
+            // - Link Card Brand is the Link Mode
+            var eligibleForLinkCardBrand: Bool {
+                elementsSession.linkFundingSources?.contains(.bankAccount) == true &&
+                !elementsSession.orderedPaymentMethodTypes.contains(.USBankAccount) &&
+                elementsSession.linkSettings?.linkMode == .linkCardBrand
+            }
+
+            if eligibleForInstantDebits {
                 let availabilityStatus = configurationSatisfiesRequirements(
                     requirements: [.financialConnectionsSDK],
                     configuration: configuration,
@@ -179,6 +196,16 @@ extension PaymentSheet {
                 if availabilityStatus == .supported {
                     recommendedPaymentMethodTypes.append(.instantDebits)
                 }
+            // Else if here so we don't show both Instant Debits and Link Card Brand together.
+            } else if eligibleForLinkCardBrand {
+                let availabilityStatus = configurationSatisfiesRequirements(
+                    requirements: [.financialConnectionsSDK],
+                    configuration: configuration,
+                    intent: intent
+                )
+                if availabilityStatus == .supported {
+                    recommendedPaymentMethodTypes.append(.linkCardBrand)
+                }
             }
 
             if let merchantPaymentMethodOrder = configuration.paymentMethodOrder?.map({ $0.lowercased() }) {

StripePaymentSheet/StripePaymentSheetTests/PaymentSheet/PaymentSheetPaymentMethodTypeTest.swift

@@ -340,6 +340,8 @@ class PaymentSheetPaymentMethodTypeTest: XCTestCase {
         XCTAssertEqual(elementsSession.orderedPaymentMethodTypes, [.klarna, .card])
     }
 
+    // MARK: - Payment Method Types
+
     func testPaymentIntentFilteredPaymentMethodTypes() {
         let intent = Intent._testPaymentIntent(paymentMethodTypes: [.card, .klarna, .przelewy24])
         var configuration = PaymentSheet.Configuration()
@@ -407,6 +409,23 @@ class PaymentSheetPaymentMethodTypeTest: XCTestCase {
         XCTAssertEqual(types, [.stripe(.card)])
     }
 
+    func testPaymentMethodTypesLinkCardBrand() {
+        let intent = Intent._testPaymentIntent(paymentMethodTypes: [.card])
+        let configuration = PaymentSheet.Configuration()
+        let types = PaymentSheet.PaymentMethodType.filteredPaymentMethodTypes(
+            from: intent,
+            elementsSession: ._testValue(
+                intent: intent,
+                linkMode: .linkCardBrand,
+                linkFundingSources: [.card, .bankAccount]
+            ),
+            configuration: configuration
+        )
+        XCTAssertEqual(types, [.stripe(.card), .linkCardBrand])
+    }
+
+    // MARK: Other
+
     func testUnknownPMTypeIsUnsupported() {
         let setupIntent = STPFixtures.makeSetupIntent(paymentMethodTypes: [.unknown])
         let paymentMethod = STPPaymentMethod.type(from: "luxe_bucks")
@@ -518,7 +537,7 @@ extension STPFixtures {
         captureMethod: String = "automatic",
         confirmationMethod: String = "automatic",
         shippingProvided: Bool = false,
-        paymentMethodJson: [String:Any]? = nil
+        paymentMethodJson: [String: Any]? = nil
     ) -> STPPaymentIntent {
         var json = STPTestUtils.jsonNamed(STPTestJSONPaymentIntent)!
         if let setupFutureUsage = setupFutureUsage {
@@ -539,7 +558,7 @@ extension STPFixtures {
         }
         if let paymentMethodJson = paymentMethodJson {
             json["payment_method"] = paymentMethodJson
-            
+
         }
         if let paymentMethodOptions = paymentMethodOptions {
             json["payment_method_options"] = paymentMethodOptions.dictionaryValue
@@ -550,7 +569,7 @@ extension STPFixtures {
     static func makeSetupIntent(
         paymentMethodTypes: [STPPaymentMethodType] = [.card],
         usage: String = "off_session",
-        paymentMethodJson: [String:Any]? = nil
+        paymentMethodJson: [String: Any]? = nil
     ) -> STPSetupIntent {
         var json = STPTestUtils.jsonNamed(STPTestJSONSetupIntent)!
         json["usage"] = usage
@@ -559,7 +578,7 @@ extension STPFixtures {
         }
         if let paymentMethodJson = paymentMethodJson {
             json["payment_method"] = paymentMethodJson
-            
+
         }
         return STPSetupIntent.decodedObject(fromAPIResponse: json)!
     }

StripePaymentSheet/StripePaymentSheetTests/PaymentSheet/STPFixtures+PaymentSheet.swift

@@ -37,6 +37,8 @@ extension STPElementsSession {
         customerSessionData: [String: Any]? = nil,
         cardBrandChoiceData: [String: Any]? = nil,
         isLinkPassthroughModeEnabled: Bool? = nil,
+        linkMode: LinkSettings.LinkMode? = nil,
+        linkFundingSources: Set<LinkSettings.FundingSource> = [],
         disableLinkSignup: Bool? = nil
     ) -> STPElementsSession {
         var json = STPTestUtils.jsonNamed("ElementsSession")!
@@ -70,6 +72,12 @@ extension STPElementsSession {
             json[jsonDict: "link_settings"]!["link_passthrough_mode_enabled"] = isLinkPassthroughModeEnabled
         }
 
+        if let linkMode {
+            json[jsonDict: "link_settings"]!["link_mode"] = linkMode.rawValue
+        }
+
+        json[jsonDict: "link_settings"]!["link_funding_sources"] = linkFundingSources.map(\.rawValue)
+
         if let disableLinkSignup {
             json[jsonDict: "link_settings"]!["link_mobile_disable_signup"] = disableLinkSignup
         }
@@ -78,7 +86,11 @@ extension STPElementsSession {
         return elementsSession
     }
 
-    static func _testValue(intent: Intent) -> STPElementsSession {
+    static func _testValue(
+        intent: Intent,
+        linkMode: LinkSettings.LinkMode? = nil,
+        linkFundingSources: Set<LinkSettings.FundingSource> = []
+    ) -> STPElementsSession {
         let paymentMethodTypes: [String] = {
             switch intent {
             case .paymentIntent(let paymentIntent):
@@ -89,7 +101,11 @@ extension STPElementsSession {
                 return intentConfig.paymentMethodTypes ?? []
             }
         }()
-        return STPElementsSession._testValue(paymentMethodTypes: paymentMethodTypes)
+        return STPElementsSession._testValue(
+            paymentMethodTypes: paymentMethodTypes,
+            linkMode: linkMode,
+            linkFundingSources: linkFundingSources
+        )
     }
 }