Implement submitStart

Samples/MobileBuyIntegration/MobileBuyIntegration/ViewControllers/ShopifyCheckoutViewController.swift

@@ -128,4 +128,25 @@ extension ShopifyCheckoutViewController: CheckoutDelegate {
         OSLogger.shared.debug("[EmbeddedCheckout] Checkout failed: \(error.localizedDescription)")
         dismiss(animated: true)
     }
+
+    func checkoutDidStartSubmit(event: CheckoutSubmitStart) {
+        // Respond with a test payment token after 1 second to simulate payment processing
+        DispatchQueue.main.asyncAfter(deadline: .now() + 1.0) {
+            let paymentToken = PaymentTokenInput(
+                token: "tok_test_123",
+                tokenType: "card",
+                tokenProvider: "delegated"
+            )
+
+            let response = CheckoutSubmitStartResponsePayload(payment: paymentToken)
+
+            OSLogger.shared.debug("[EmbeddedCheckout] Attempting to respond with test payment token")
+            do {
+                try event.respondWith(payload: response)
+                OSLogger.shared.debug("[EmbeddedCheckout] Successfully sent response")
+            } catch {
+                OSLogger.shared.error("[EmbeddedCheckout] Failed to respond to submit start: \(error)")
+            }
+        }
+    }
 }

Sources/ShopifyCheckoutSheetKit/CheckoutDelegate.swift

@@ -53,6 +53,12 @@ public protocol CheckoutDelegate: AnyObject {
 
     /// Tells the delegate that the checkout is requesting card change intent (e.g., for native card picker)
     func checkoutDidRequestCardChange(event: CheckoutCardChangeRequested)
+
+    /// Tells the delegate that the buyer has attempted to submit the checkout.
+    ///
+    /// This event is only emitted when native payment delegation is configured for the authenticated app.
+    /// When triggered, you can provide payment tokens, update cart data, or handle custom submission logic.
+    func checkoutDidStartSubmit(event: CheckoutSubmitStart)
 }
 
 extension CheckoutDelegate {
@@ -84,6 +90,10 @@ extension CheckoutDelegate {
         /// No-op by default
     }
 
+    public func checkoutDidStartSubmit(event _: CheckoutSubmitStart) {
+        /// No-op by default
+    }
+
     private func handleUrl(_ url: URL) {
         if UIApplication.shared.canOpenURL(url) {
             UIApplication.shared.open(url)

Sources/ShopifyCheckoutSheetKit/CheckoutSubmitStart.swift

@@ -0,0 +1,46 @@
+/*
+ MIT License
+
+ Copyright 2023 - Present, Shopify Inc.
+
+ Permission is hereby granted, free of charge, to any person obtaining a copy
+ of this software and associated documentation files (the "Software"), to deal
+ in the Software without restriction, including without limitation the rights
+ to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
+ copies of the Software, and to permit persons to whom the Software is
+ furnished to do so, subject to the following conditions:
+
+ The above copyright notice and this permission notice shall be included in all
+ copies or substantial portions of the Software.
+
+ THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
+ IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
+ FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
+ AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
+ LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
+ OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE SOFTWARE.
+ */
+
+import Foundation
+import WebKit
+
+public final class CheckoutSubmitStart: BaseRPCRequest<CheckoutSubmitStartParams, CheckoutSubmitStartResponsePayload> {
+    override public static var method: String { "checkout.submitStart" }
+}
+
+public struct CheckoutSubmitStartParams: Codable {
+    public let cart: Cart
+    public let checkout: Checkout
+}
+
+public struct CheckoutSubmitStartResponsePayload: Codable {
+    public let payment: PaymentTokenInput?
+    public let cart: CartInput?
+    public let errors: [ResponseError]?
+
+    public init(payment: PaymentTokenInput? = nil, cart: CartInput? = nil, errors: [ResponseError]? = nil) {
+        self.payment = payment
+        self.cart = cart
+        self.errors = errors
+    }
+}

Sources/ShopifyCheckoutSheetKit/CheckoutWebView.swift

@@ -34,6 +34,7 @@ protocol CheckoutWebViewDelegate: AnyObject {
     func checkoutViewDidToggleModal(modalVisible: Bool)
     func checkoutViewDidStartAddressChange(event: CheckoutAddressChangeStart)
     func checkoutViewDidRequestCardChange(event: CheckoutCardChangeRequested)
+    func checkoutViewDidStartSubmit(event: CheckoutSubmitStart)
 }
 
 private let deprecatedReasonHeader = "x-shopify-api-deprecated-reason"
@@ -298,6 +299,12 @@ extension CheckoutWebView: WKScriptMessageHandler {
             )
             viewDelegate.checkoutViewDidRequestCardChange(event: cardRequest)
 
+        case let submitRequest as CheckoutSubmitStart:
+            OSLogger.shared.info(
+                "Checkout submit start event received"
+            )
+            viewDelegate.checkoutViewDidStartSubmit(event: submitRequest)
+
         case let errorRequest as CheckoutErrorRequest:
             handleCheckoutError(errorRequest)
 

Sources/ShopifyCheckoutSheetKit/CheckoutWebViewController.swift

@@ -267,6 +267,10 @@ extension CheckoutWebViewController: CheckoutWebViewDelegate {
         delegate?.checkoutDidRequestCardChange(event: event)
     }
 
+    func checkoutViewDidStartSubmit(event: CheckoutSubmitStart) {
+        delegate?.checkoutDidStartSubmit(event: event)
+    }
+
     private func isRecoverableError() -> Bool {
         /// Reuse of multipass tokens will cause 422 errors. A new token must be generated
         return !CheckoutURL(from: checkoutURL).isMultipassURL()

Sources/ShopifyCheckoutSheetKit/RPCRequestRegistry.swift

@@ -33,7 +33,8 @@ enum RPCRequestRegistry {
         CheckoutCompleteRequest.self,
         CheckoutErrorRequest.self,
         CheckoutModalToggledRequest.self,
-        CheckoutStartRequest.self
+        CheckoutStartRequest.self,
+        CheckoutSubmitStart.self
     ]
 
     /// Find the request type for a given method name

Sources/ShopifyCheckoutSheetKit/Types.swift

@@ -454,3 +454,30 @@ public struct ResponseError: Codable {
         self.fieldTarget = fieldTarget
     }
 }
+
+// MARK: - Payment Token Types
+
+/// Payment token input structure for checkout submission.
+public struct PaymentTokenInput: Codable {
+    public let token: String
+    public let tokenType: String
+    public let tokenProvider: String
+
+    public init(token: String, tokenType: String, tokenProvider: String) {
+        self.token = token
+        self.tokenType = tokenType
+        self.tokenProvider = tokenProvider
+    }
+}
+
+// MARK: - Checkout Session
+
+/// Checkout session information.
+public struct Checkout: Codable {
+    /// The checkout session identifier
+    public let id: String
+
+    public init(id: String) {
+        self.id = id
+    }
+}

Tests/ShopifyCheckoutSheetKitTests/CheckoutAddressChangeStartTests.swift

@@ -25,6 +25,49 @@
 import XCTest
 
 class CheckoutAddressChangeStartTests: XCTestCase {
+    // MARK: - Response Tests
+
+    func testRespondWithSendsJavaScriptToWebView() throws {
+        let mockWebView = MockWebView()
+        let params = CheckoutAddressChangeStartParams(
+            addressType: "shipping",
+            cart: createTestCart()
+        )
+        let request = CheckoutAddressChangeStart(id: "test-id-789", params: params)
+        request.webview = mockWebView
+
+        let payload = CheckoutAddressChangeStartResponsePayload(
+            cart: CartInput(
+                delivery: CartDeliveryInput(
+                    addresses: [
+                        CartSelectableAddressInput(
+                            address: CartDeliveryAddressInput(countryCode: "US")
+                        )
+                    ]
+                )
+            )
+        )
+
+        let expectation = expectation(description: "JavaScript executed")
+        mockWebView.evaluateJavaScriptExpectation = expectation
+
+        try request.respondWith(payload: payload)
+
+        waitForExpectations(timeout: 2.0)
+
+        // Verify the JavaScript was executed and contains the expected JSON-RPC response
+        XCTAssertNotNil(mockWebView.capturedJavaScript, "JavaScript should have been executed")
+
+        let capturedJS = mockWebView.capturedJavaScript ?? ""
+
+        // Verify the response contains expected JSON-RPC fields
+        XCTAssertTrue(capturedJS.contains("window.postMessage"), "Should call window.postMessage")
+        XCTAssertTrue(capturedJS.contains("\"jsonrpc\":\"2.0\""), "Should include JSON-RPC version")
+        XCTAssertTrue(capturedJS.contains("\"id\":\"test-id-789\""), "Should include request ID")
+        XCTAssertTrue(capturedJS.contains("\"result\""), "Should include result field")
+        XCTAssertTrue(capturedJS.contains("\"cart\""), "Should include cart in result")
+    }
+
     // MARK: - Validation Tests
 
     func testValidateAcceptsValid2CharacterCountryCode() throws {

Tests/ShopifyCheckoutSheetKitTests/CheckoutBridgeTests.swift

@@ -302,4 +302,61 @@ class CheckoutBridgeTests: XCTestCase {
         XCTAssertEqual("gid://shopify/Order/test-order-123", completeRequest.params.orderConfirmation.order.id)
         XCTAssertEqual("gid://shopify/Cart/test-cart-123", completeRequest.params.cart.id)
     }
+
+    func testDecodeSupportsCheckoutSubmitStart() throws {
+        let mock = WKScriptMessageMock(
+            body: """
+            {
+                "jsonrpc": "2.0",
+                "method": "checkout.submitStart",
+                "id": "submit-123",
+                "params": {
+                    "cart": {
+                        "id": "gid://shopify/Cart/test-cart-456",
+                        "lines": [],
+                        "cost": {
+                            "subtotalAmount": {
+                                "amount": "100.00",
+                                "currencyCode": "USD"
+                            },
+                            "totalAmount": {
+                                "amount": "100.00",
+                                "currencyCode": "USD"
+                            }
+                        },
+                        "buyerIdentity": {
+                            "email": "[email protected]",
+                            "phone": null,
+                            "customer": null,
+                            "countryCode": "US"
+                        },
+                        "deliveryGroups": [],
+                        "discountCodes": [],
+                        "appliedGiftCards": [],
+                        "discountAllocations": [],
+                        "delivery": {
+                            "addresses": []
+                        }
+                    },
+                    "checkout": {
+                        "id": "checkout-session-789"
+                    }
+                }
+            }
+            """,
+            webView: mockWebView
+        )
+
+        let result = try CheckoutBridge.decode(mock)
+
+        guard let submitRequest = result as? CheckoutSubmitStart else {
+            XCTFail("Expected CheckoutSubmitStart, got \(result)")
+            return
+        }
+
+        XCTAssertEqual("submit-123", submitRequest.id)
+        XCTAssertEqual("gid://shopify/Cart/test-cart-456", submitRequest.params.cart.id)
+        XCTAssertEqual("checkout-session-789", submitRequest.params.checkout.id)
+        XCTAssertEqual("[email protected]", submitRequest.params.cart.buyerIdentity.email)
+    }
 }

Tests/ShopifyCheckoutSheetKitTests/CheckoutSubmitStartTests.swift

@@ -0,0 +1,90 @@
+/*
+ MIT License
+
+ Copyright 2023 - Present, Shopify Inc.
+
+ Permission is hereby granted, free of charge, to any person obtaining a copy
+ of this software and associated documentation files (the "Software"), to deal
+ in the Software without restriction, including without limitation the rights
+ to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
+ copies of the Software, and to permit persons to whom the Software is
+ furnished to do so, subject to the following conditions:
+
+ The above copyright notice and this permission notice shall be included in all
+ copies or substantial portions of the Software.
+
+ THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
+ IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
+ FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
+ AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
+ LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
+ OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE SOFTWARE.
+ */
+
+@testable import ShopifyCheckoutSheetKit
+import XCTest
+
+class CheckoutSubmitStartTests: XCTestCase {
+    // MARK: - Response Tests
+
+    func testRespondWithSendsJavaScriptToWebView() throws {
+        let mockWebView = MockWebView()
+        let params = CheckoutSubmitStartParams(
+            cart: createTestCart(),
+            checkout: Checkout(id: "test-checkout-123")
+        )
+        let request = CheckoutSubmitStart(id: "test-id-456", params: params)
+        request.webview = mockWebView
+
+        let payload = CheckoutSubmitStartResponsePayload(payment: nil, cart: nil, errors: nil)
+
+        let expectation = expectation(description: "JavaScript executed")
+        mockWebView.evaluateJavaScriptExpectation = expectation
+
+        try request.respondWith(payload: payload)
+
+        waitForExpectations(timeout: 2.0)
+
+        // Verify the JavaScript was executed and contains the expected JSON-RPC response
+        XCTAssertNotNil(mockWebView.capturedJavaScript, "JavaScript should have been executed")
+
+        let capturedJS = mockWebView.capturedJavaScript ?? ""
+
+        // Verify the response contains expected JSON-RPC fields
+        XCTAssertTrue(capturedJS.contains("window.postMessage"), "Should call window.postMessage")
+        XCTAssertTrue(capturedJS.contains("\"jsonrpc\":\"2.0\""), "Should include JSON-RPC version")
+        XCTAssertTrue(capturedJS.contains("\"id\":\"test-id-456\""), "Should include request ID")
+        XCTAssertTrue(capturedJS.contains("\"result\""), "Should include result field")
+    }
+
+    // MARK: - Decoding Tests
+
+    func testDecodesCheckoutSessionId() throws {
+        let json = """
+        {
+            "cart": {
+                "id": "gid://shopify/Cart/test-cart-789",
+                "lines": [],
+                "cost": {
+                    "subtotalAmount": {"amount": "75.00", "currencyCode": "CAD"},
+                    "totalAmount": {"amount": "75.00", "currencyCode": "CAD"}
+                },
+                "buyerIdentity": {},
+                "deliveryGroups": [],
+                "discountCodes": [],
+                "appliedGiftCards": [],
+                "discountAllocations": [],
+                "delivery": {"addresses": []}
+            },
+            "checkout": {
+                "id": "checkout-session-123"
+            }
+        }
+        """
+
+        let data = json.data(using: .utf8)!
+        let params = try JSONDecoder().decode(CheckoutSubmitStartParams.self, from: data)
+
+        XCTAssertEqual(params.checkout.id, "checkout-session-123")
+    }
+}

Tests/ShopifyCheckoutSheetKitTests/Mocks/MockCheckoutWebViewDelegate.swift

@@ -95,4 +95,8 @@ class MockCheckoutWebViewDelegate: CheckoutWebViewDelegate {
     func checkoutViewDidRequestCardChange(event _: CheckoutCardChangeRequested) {
         // No-op for tests unless explicitly asserted
     }
+
+    func checkoutViewDidStartSubmit(event _: CheckoutSubmitStart) {
+        // No-op for tests unless explicitly asserted
+    }
 }

Tests/ShopifyCheckoutSheetKitTests/Mocks/MockWebView.swift

@@ -26,12 +26,13 @@ import WebKit
 import XCTest
 
 class MockWebView: CheckoutWebView {
-    var expectedScript = ""
-
     var evaluateJavaScriptExpectation: XCTestExpectation?
 
+    var capturedJavaScript: String?
+
     override func evaluateJavaScript(_ javaScriptString: String) async throws -> Any {
-        if javaScriptString == expectedScript {
+        capturedJavaScript = javaScriptString
+        if !javaScriptString.isEmpty {
             evaluateJavaScriptExpectation?.fulfill()
         }
         return true