Move consumer session creation before verification screens (#4632)

## Summary
<!-- Simple summary of what was changed. -->

This pull request aligns the Financial Connections iOS SDK with Android
and Web, where we create a consumer session before we display any
verification screens. This removes a decent amount of error handling
code (for very unlikely errors) and will make implementing
#4272 correctly easier.

## Motivation
<!-- Why are you making this change? If it's for fixing a bug, if
possible, please include a code snippet or example project that
demonstrates the issue. -->

## Testing
<!-- How was the code tested? Be as specific as possible. -->

## Changelog
<!-- Is this a notable change that affects users? If so, add a line to
`CHANGELOG.md` and prefix the line with one of the following:
    - [Added] for new features.
    - [Changed] for changes in existing functionality.
    - [Deprecated] for soon-to-be removed features.
    - [Removed] for now removed features.
    - [Fixed] for any bug fixes.
    - [Security] in case of vulnerabilities.
-->

---------

Co-authored-by: Mat Schmid <[email protected]>

Author: tillh-stripe

StripeFinancialConnections/StripeFinancialConnections/Source/Native/NativeFlowController.swift

@@ -1031,8 +1031,12 @@ extension NativeFlowController: NetworkingLinkSignupViewControllerDelegate {
 extension NativeFlowController: NetworkingLinkLoginWarmupViewControllerDelegate {
 
     func networkingLinkLoginWarmupViewControllerDidSelectContinue(
-        _ viewController: NetworkingLinkLoginWarmupViewController
+        _ viewController: NetworkingLinkLoginWarmupViewController,
+        withSession consumerSession: ConsumerSessionData,
+        consumerPublishableKey: String
     ) {
+        dataManager.consumerSession = consumerSession
+        dataManager.consumerPublishableKey = consumerPublishableKey
         pushPane(.networkingLinkVerification, animated: true)
     }
 
@@ -1063,6 +1067,17 @@ extension NativeFlowController: NetworkingLinkLoginWarmupViewControllerDelegate
     ) {
         showTerminalError(error)
     }
+
+    func networkingLinkLoginWarmupViewControllerDidFailAttestationVerdict(
+        _ viewController: NetworkingLinkLoginWarmupViewController,
+        prefillDetails: WebPrefillDetails
+    ) {
+        delegate?.nativeFlowController(
+            self,
+            shouldLaunchWebFlow: dataManager.manifest,
+            prefillDetails: prefillDetails
+        )
+    }
 }
 
 // MARK: - TerminalErrorViewControllerDelegate
@@ -1119,10 +1134,6 @@ extension NativeFlowController: AttachLinkedPaymentAccountViewControllerDelegate
 // MARK: - NetworkingLinkVerificationViewControllerDelegate
 
 extension NativeFlowController: NetworkingLinkVerificationViewControllerDelegate {
-    func networkingLinkVerificationViewController(_ viewController: NetworkingLinkVerificationViewController, didReceiveConsumerPublishableKey consumerPublishableKey: String) {
-        dataManager.consumerPublishableKey = consumerPublishableKey
-    }
-
     func networkingLinkVerificationViewController(
         _ viewController: NetworkingLinkVerificationViewController,
         didRequestNextPane nextPane: FinancialConnectionsSessionManifest.NextPane,
@@ -1139,17 +1150,6 @@ extension NativeFlowController: NetworkingLinkVerificationViewControllerDelegate
     ) {
         showTerminalError(error)
     }
-
-    func networkingLinkVerificationViewControllerDidFailAttestationVerdict(
-        _ viewController: NetworkingLinkVerificationViewController,
-        prefillDetails: WebPrefillDetails
-    ) {
-        delegate?.nativeFlowController(
-            self,
-            shouldLaunchWebFlow: dataManager.manifest,
-            prefillDetails: prefillDetails
-        )
-    }
 }
 
 // MARK: - LinkAccountPickerViewControllerDelegate
@@ -1219,10 +1219,6 @@ extension NativeFlowController: LinkAccountPickerViewControllerDelegate {
 
 extension NativeFlowController: NetworkingSaveToLinkVerificationViewControllerDelegate {
 
-    func networkingSaveToLinkVerificationViewController(_ viewController: NetworkingSaveToLinkVerificationViewController, didReceiveConsumerPublishableKey consumerPublishableKey: String) {
-        dataManager.consumerPublishableKey = consumerPublishableKey
-    }
-
     func networkingSaveToLinkVerificationViewControllerDidFinish(
         _ viewController: NetworkingSaveToLinkVerificationViewController,
         saveToLinkWithStripeSucceeded: Bool?,
@@ -1241,27 +1237,12 @@ extension NativeFlowController: NetworkingSaveToLinkVerificationViewControllerDe
     ) {
         showTerminalError(error)
     }
-
-    func networkingSaveToLinkVerificationViewControllerDidFailAttestationVerdict(
-        _ viewController: NetworkingSaveToLinkVerificationViewController,
-        prefillDetails: WebPrefillDetails
-    ) {
-        delegate?.nativeFlowController(
-            self,
-            shouldLaunchWebFlow: dataManager.manifest,
-            prefillDetails: prefillDetails
-        )
-    }
 }
 
 // MARK: - NetworkingLinkStepUpVerificationViewControllerDelegate
 
 extension NativeFlowController: NetworkingLinkStepUpVerificationViewControllerDelegate {
 
-    func networkingLinkStepUpVerificationViewController(_ viewController: NetworkingLinkStepUpVerificationViewController, didReceiveConsumerPublishableKey consumerPublishableKey: String) {
-        dataManager.consumerPublishableKey = consumerPublishableKey
-    }
-
     func networkingLinkStepUpVerificationViewController(
         _ viewController: NetworkingLinkStepUpVerificationViewController,
         didCompleteVerificationWithInstitution institution: FinancialConnectionsInstitution?,
@@ -1281,23 +1262,6 @@ extension NativeFlowController: NetworkingLinkStepUpVerificationViewControllerDe
     ) {
         showTerminalError(error)
     }
-
-    func networkingLinkStepUpVerificationViewControllerEncounteredSoftError(
-        _ viewController: NetworkingLinkStepUpVerificationViewController
-    ) {
-        pushPane(.institutionPicker, animated: true)
-    }
-
-    func networkingLinkStepUpVerificationViewControllerDidFailAttestationVerdict(
-        _ viewController: NetworkingLinkStepUpVerificationViewController,
-        prefillDetails: WebPrefillDetails
-    ) {
-        delegate?.nativeFlowController(
-            self,
-            shouldLaunchWebFlow: dataManager.manifest,
-            prefillDetails: prefillDetails
-        )
-    }
 }
 
 // MARK: - LinkLoginViewControllerDelegate
@@ -1538,15 +1502,13 @@ private func CreatePaneViewController(
         networkingLinkSignupViewController.delegate = nativeFlowController
         viewController = networkingLinkSignupViewController
     case .networkingLinkVerification:
-        let accountholderCustomerEmailAddress = dataManager.manifest.accountholderCustomerEmailAddress
-        let consumerSessionEmailAddress = dataManager.consumerSession?.emailAddress
-        if let accountholderCustomerEmailAddress = consumerSessionEmailAddress ?? accountholderCustomerEmailAddress {
+        if let consumerSession = dataManager.consumerSession {
             let networkingLinkVerificationDataSource = NetworkingLinkVerificationDataSourceImplementation(
-                accountholderCustomerEmailAddress: accountholderCustomerEmailAddress,
                 manifest: dataManager.manifest,
                 apiClient: dataManager.apiClient,
                 clientSecret: dataManager.clientSecret,
                 returnURL: dataManager.returnURL,
+                consumerSession: consumerSession,
                 analyticsClient: dataManager.analyticsClient
             )
             let networkingLinkVerificationViewController = NetworkingLinkVerificationViewController(dataSource: networkingLinkVerificationDataSource)
@@ -1557,9 +1519,7 @@ private func CreatePaneViewController(
             viewController = nil
         }
     case .networkingSaveToLinkVerification:
-        if
-            let consumerSession = dataManager.consumerSession
-        {
+        if let consumerSession = dataManager.consumerSession {
             let networkingSaveToLinkVerificationDataSource = NetworkingSaveToLinkVerificationDataSourceImplementation(
                 manifest: dataManager.manifest,
                 consumerSession: consumerSession,
@@ -1667,7 +1627,8 @@ private func CreatePaneViewController(
             apiClient: dataManager.apiClient,
             clientSecret: dataManager.clientSecret,
             analyticsClient: dataManager.analyticsClient,
-            nextPaneOrDrawerOnSecondaryCta: parameters?.nextPaneOrDrawerOnSecondaryCta
+            nextPaneOrDrawerOnSecondaryCta: parameters?.nextPaneOrDrawerOnSecondaryCta,
+            elementsSessionContext: dataManager.elementsSessionContext
         )
         let networkingLinkWarmupViewController = NetworkingLinkLoginWarmupViewController(
             dataSource: networkingLinkWarmupDataSource,

StripeFinancialConnections/StripeFinancialConnections/Source/Native/NetworkingLinkLoginWarmup/NetworkingLinkLoginWarmupDataSource.swift

@@ -11,8 +11,14 @@ import Foundation
 protocol NetworkingLinkLoginWarmupDataSource: AnyObject {
     var manifest: FinancialConnectionsSessionManifest { get }
     var analyticsClient: FinancialConnectionsAnalyticsClient { get }
+    var email: String? { get }
 
+    func lookupConsumerSession() -> Future<LookupConsumerSessionResponse>
     func disableNetworking() -> Future<FinancialConnectionsSessionManifest>
+    func completeAssertionIfNeeded(
+        possibleError: Error?,
+        api: FinancialConnectionsAPIClientLogger.API
+    ) -> Error?
 }
 
 final class NetworkingLinkLoginWarmupDataSourceImplementation: NetworkingLinkLoginWarmupDataSource {
@@ -22,19 +28,46 @@ final class NetworkingLinkLoginWarmupDataSourceImplementation: NetworkingLinkLog
     private let clientSecret: String
     let analyticsClient: FinancialConnectionsAnalyticsClient
     private let nextPaneOrDrawerOnSecondaryCta: String?
+    private let elementsSessionContext: ElementsSessionContext?
+
+    var email: String? {
+        manifest.accountholderCustomerEmailAddress ?? elementsSessionContext?.prefillDetails?.email
+    }
 
     init(
         manifest: FinancialConnectionsSessionManifest,
         apiClient: any FinancialConnectionsAPI,
         clientSecret: String,
         analyticsClient: FinancialConnectionsAnalyticsClient,
-        nextPaneOrDrawerOnSecondaryCta: String?
+        nextPaneOrDrawerOnSecondaryCta: String?,
+        elementsSessionContext: ElementsSessionContext?
     ) {
         self.manifest = manifest
         self.apiClient = apiClient
         self.clientSecret = clientSecret
         self.analyticsClient = analyticsClient
         self.nextPaneOrDrawerOnSecondaryCta = nextPaneOrDrawerOnSecondaryCta
+        self.elementsSessionContext = elementsSessionContext
+    }
+
+    func lookupConsumerSession() -> Future<LookupConsumerSessionResponse> {
+        guard let email else {
+            let error = FinancialConnectionsSheetError.unknown(debugDescription: "Unexpected nil email in warmup data source")
+            analyticsClient.logUnexpectedError(
+                error,
+                errorName: "NoEmailInWarmupPaneError",
+                pane: .networkingLinkLoginWarmup
+            )
+            return Promise(error: error)
+        }
+        return apiClient.consumerSessionLookup(
+            emailAddress: email,
+            clientSecret: clientSecret,
+            sessionId: manifest.id,
+            emailSource: .customerObject,
+            useMobileEndpoints: manifest.verified,
+            pane: .networkingLinkLoginWarmup
+        )
     }
 
     func disableNetworking() -> Future<FinancialConnectionsSessionManifest> {
@@ -44,4 +77,17 @@ final class NetworkingLinkLoginWarmupDataSourceImplementation: NetworkingLinkLog
             clientSecret: clientSecret
         )
     }
+
+    // Marks the assertion as completed and logs possible errors during verified flows.
+    func completeAssertionIfNeeded(
+        possibleError: Error?,
+        api: FinancialConnectionsAPIClientLogger.API
+    ) -> Error? {
+        guard manifest.verified else { return nil }
+        return apiClient.completeAssertion(
+            possibleError: possibleError,
+            api: api,
+            pane: .networkingLinkLoginWarmup
+        )
+    }
 }