[Link] Determine payment types from funding sources (#2075)

* [Link] Determine payment types from funding sources

* Fix tests

* Add link_settings to JSON mocks

* Put link_settings where it belongs

* Add explanatory comments around JSON parsing

StripePaymentSheet/StripePaymentSheet/Helpers/PaymentSheetLinkAccount.swift

@@ -472,7 +472,7 @@ extension PaymentSheetLinkAccount {
     /// - Parameter intent: The Intent that the user is trying to confirm.
     /// - Returns: A set containing the supported Payment Details types.
     func supportedPaymentDetailsTypes(for intent: Intent) -> Set<ConsumerPaymentDetails.DetailsType> {
-        guard let currentSession = currentSession else {
+        guard let currentSession = currentSession, let fundingSources = intent.linkFundingSources else {
             return []
         }
 
@@ -480,10 +480,12 @@ extension PaymentSheetLinkAccount {
             currentSession.supportedPaymentDetailsTypes ?? []
         )
 
-        if !intent.linkBankOnboardingEnabled {
-            supportedPaymentDetailsTypes.remove(.bankAccount)
-        }
+        // Take the intersection of the consumer session types and the merchant-provided Link funding sources
+        let fundingSourceDetailsTypes = Set(fundingSources.compactMap { $0.detailsType })
 
+        supportedPaymentDetailsTypes.formIntersection(fundingSourceDetailsTypes)
+
+        // Special testmode handling
         if !intent.livemode && Self.emailSupportsMultipleFundingSourcesOnTestMode(email) {
             supportedPaymentDetailsTypes.insert(.bankAccount)
         }
@@ -526,3 +528,16 @@ private extension PaymentSheetLinkAccount {
     }
 
 }
+
+private extension LinkSettings.FundingSource {
+    var detailsType: ConsumerPaymentDetails.DetailsType? {
+        switch self {
+        case .card:
+            return .card
+        case .bankAccount:
+            return .bankAccount
+        @unknown default:
+            return nil
+        }
+    }
+}

StripePaymentSheet/StripePaymentSheet/Internal/Link/Extensions/Intent+Link.swift

@@ -18,12 +18,12 @@ extension Intent {
         }
     }
 
-    var linkBankOnboardingEnabled: Bool {
+    var linkFundingSources: Set<LinkSettings.FundingSource>? {
         switch self {
         case .paymentIntent(let paymentIntent):
-            return paymentIntent.linkSettings?.bankOnboardingEnabled ?? false
+            return paymentIntent.linkSettings?.fundingSources
         case .setupIntent(let setupIntent):
-            return setupIntent.linkSettings?.bankOnboardingEnabled ?? false
+            return setupIntent.linkSettings?.fundingSources
         }
     }
 

StripePayments/StripePayments/API Bindings/Models/Shared/LinkSettings.swift

@@ -11,16 +11,20 @@ import Foundation
 /// For internal SDK use only
 @objc(STP_Internal_LinkSettings)
 @_spi(STP) public final class LinkSettings: NSObject, STPAPIResponseDecodable {
+    @_spi(STP) public enum FundingSource: String {
+        case card = "CARD"
+        case bankAccount = "BANK_ACCOUNT"
+    }
 
-    @_spi(STP) public let bankOnboardingEnabled: Bool
+    @_spi(STP) public let fundingSources: Set<FundingSource>
 
     @_spi(STP) public let allResponseFields: [AnyHashable: Any]
 
     @_spi(STP) public init(
-        bankOnboardingEnabled: Bool,
+        fundingSources: Set<FundingSource>,
         allResponseFields: [AnyHashable: Any]
     ) {
-        self.bankOnboardingEnabled = bankOnboardingEnabled
+        self.fundingSources = fundingSources
         self.allResponseFields = allResponseFields
     }
 
@@ -29,13 +33,16 @@ import Foundation
     ) -> Self? {
         guard
             let response = response,
-            let bankOnboardingEnabled = response["link_bank_onboarding_enabled"] as? Bool
+            let fundingSourcesStrings = response["link_funding_sources"] as? [String]
         else {
             return nil
         }
 
+        // Server may send down funding sources we haven't implemented yet, so we'll just ignore any unknown sources
+        let validFundingSources = Set(fundingSourcesStrings.compactMap(FundingSource.init))
+
         return LinkSettings(
-            bankOnboardingEnabled: bankOnboardingEnabled,
+            fundingSources: validFundingSources,
             allResponseFields: response
         ) as? Self
     }

Tests/Tests/PayWithLinkViewController-WalletViewModelTests.swift

@@ -106,10 +106,17 @@ class PayWithLinkViewController_WalletViewModelTests: XCTestCase {
 extension PayWithLinkViewController_WalletViewModelTests {
 
     func makeSUT() throws -> PayWithLinkViewController.WalletViewModel {
+        // Link settings don't live in the PaymentIntent object itself, but in the /elements/sessions API response
+        // So we construct a minimal response (see STPPaymentIntentTest.testDecodedObjectFromAPIResponseMapping) to parse them
+        let paymentIntentJson = try XCTUnwrap(STPTestUtils.jsonNamed(STPTestJSONPaymentIntent))
+        let orderedPaymentJson = ["card", "link"]
+        let paymentIntentResponse = ["payment_intent": paymentIntentJson,
+                                     "ordered_payment_method_types": orderedPaymentJson] as [String : Any]
+        let linkSettingsJson = ["link_funding_sources": ["CARD"]]
+        let response = ["payment_method_preference": paymentIntentResponse,
+                        "link_settings": linkSettingsJson]
         let paymentIntent = try XCTUnwrap(
-            STPPaymentIntent.decodedObject(
-                fromAPIResponse: STPTestUtils.jsonNamed(STPTestJSONPaymentIntent)
-            )
+            STPPaymentIntent.decodedObject(fromAPIResponse: response)
         )
 
         return PayWithLinkViewController.WalletViewModel(