From debae23bc89d05b3cfbd18b84a8f3662833a1f86 Mon Sep 17 00:00:00 2001
From: Seth Friedman <sfriedman@stripe.com>
Date: Thu, 27 Apr 2023 00:06:58 -0400
Subject: [PATCH] Add validation to catch blank ephemeral keys in
 CustomerConfiguration

We currently don't validate that an ephemeral key is non-empty when a
user includes it in the `CustomerConfiguration`. This ends up giving
users a pretty obscure error in the API response, and is difficult to
debug today.

Including this validation will catch this issue early and provide users
a better debugging experience.
---
 StripePaymentSheet/Project.swift              |  2 +-
 .../PaymentSheetConfiguration.swift           |  4 +++-
 .../PaymentSheetConfigurationTests.swift      | 21 +++++++++++++++++++
 3 files changed, 25 insertions(+), 2 deletions(-)
 create mode 100644 StripePaymentSheet/StripePaymentSheetTests/PaymentSheetConfigurationTests.swift

diff --git a/StripePaymentSheet/Project.swift b/StripePaymentSheet/Project.swift
index ce7432d8e45..e2f308f6e65 100644
--- a/StripePaymentSheet/Project.swift
+++ b/StripePaymentSheet/Project.swift
@@ -12,5 +12,5 @@ let project = Project.stripeFramework(
         .project(target: "StripePayments", path: "//StripePayments"),
         .project(target: "StripePaymentsUI", path: "//StripePaymentsUI"),
     ],
-    unitTestOptions: .testOptions()
+    unitTestOptions: .testOptions(usesPreconditionTesting: true)
 )
diff --git a/StripePaymentSheet/StripePaymentSheet/Source/PaymentSheet/PaymentSheetConfiguration.swift b/StripePaymentSheet/StripePaymentSheet/Source/PaymentSheet/PaymentSheetConfiguration.swift
index c37163592c0..6c7630cbe14 100644
--- a/StripePaymentSheet/StripePaymentSheet/Source/PaymentSheet/PaymentSheetConfiguration.swift
+++ b/StripePaymentSheet/StripePaymentSheet/Source/PaymentSheet/PaymentSheetConfiguration.swift
@@ -172,11 +172,13 @@ extension PaymentSheet {
         /// See https://stripe.com/docs/api/customers/object#customer_object-id
         public let id: String
 
-        /// A short-lived token that allows the SDK to access a Customer's payment methods
+        /// A short-lived token that allows the SDK to access a Customer's payment methods. Cannot be empty
         public let ephemeralKeySecret: String
 
         /// Initializes a CustomerConfiguration
         public init(id: String, ephemeralKeySecret: String) {
+            assert(!ephemeralKeySecret.isEmpty, "Ephemeral key secret cannot be empty")
+
             self.id = id
             self.ephemeralKeySecret = ephemeralKeySecret
         }
diff --git a/StripePaymentSheet/StripePaymentSheetTests/PaymentSheetConfigurationTests.swift b/StripePaymentSheet/StripePaymentSheetTests/PaymentSheetConfigurationTests.swift
new file mode 100644
index 00000000000..dc8e9241899
--- /dev/null
+++ b/StripePaymentSheet/StripePaymentSheetTests/PaymentSheetConfigurationTests.swift
@@ -0,0 +1,21 @@
+//
+//  PaymentSheetConfigurationTests.swift
+//  StripePaymentSheetTests
+//
+//  Copyright © 2023 Stripe, Inc. All rights reserved.
+//
+
+import CwlPreconditionTesting
+import StripePaymentSheet
+import XCTest
+
+final class PaymentSheetConfigurationTests: XCTestCase {
+
+    func test_customerConfigurationInit_assertsWhenEphemeralKeyIsBlank() throws {
+        let exception = catchBadInstruction {
+            _ = PaymentSheet.CustomerConfiguration(id: "foo", ephemeralKeySecret: "")
+        }
+
+        XCTAssertNotNil(exception)
+    }
+}