Improved error handling and added tests

Sources/Error Handling/ErrorUtils.swift

@@ -408,9 +408,11 @@ enum ErrorUtils {
      */
     static func invalidPromotionalOfferError(
         error: Error? = nil,
+        message: String? = nil,
         fileName: String = #fileID, functionName: String = #function, line: UInt = #line
     ) -> PurchasesError {
         return ErrorUtils.error(with: .invalidPromotionalOfferError,
+                                message: message,
                                 underlyingError: error)
     }
 

Sources/Purchasing/Purchases/PurchasesOrchestrator.swift

@@ -434,7 +434,7 @@ final class PurchasesOrchestrator {
                         Logger.debug(
                             Strings.storeKit.sk2_purchasing_added_promotional_offer_option(signedData.identifier)
                         )
-                        options.insert(signedData.sk2PurchaseOption)
+                        options.insert(try signedData.sk2PurchaseOption)
                     }
 
                     return try await sk2Product.purchase(options: options)
@@ -446,6 +446,9 @@ final class PurchasesOrchestrator {
                                                                               fetchPolicy: .cachedOrFetched),
                 userCancelled: true
             )
+        } catch let error as PromotionalOffer.SignedData.Error {
+            throw ErrorUtils.invalidPromotionalOfferError(error: error,
+                                                          message: error.localizedDescription)
         } catch {
             throw ErrorUtils.purchasesError(withStoreKitError: error)
         }

Sources/Purchasing/StoreKitAbstractions/PromotionalOffer.swift

@@ -102,6 +102,13 @@ extension PromotionalOffer.SignedData: @unchecked Sendable {}
 
 extension PromotionalOffer.SignedData {
 
+    enum Error: Swift.Error {
+
+        /// The signature generated by the backend could not be decoded.
+        case failedToDecodeSignature(String)
+
+    }
+
     @available(iOS 12.2, macOS 10.14.4, watchOS 6.2, macCatalyst 13.0, tvOS 12.2, *)
     convenience init(sk1PaymentDiscount discount: SKPaymentDiscount) {
         self.init(identifier: discount.identifier,
@@ -122,22 +129,36 @@ extension PromotionalOffer.SignedData {
 
     @available(iOS 15.0, tvOS 15.0, watchOS 8.0, macOS 12.0, *)
     var sk2PurchaseOption: Product.PurchaseOption {
-        let signature: Data
-
-        if let decoded = Data(base64Encoded: self.signature) {
-            signature = decoded
-        } else {
-            // TODO: log warning
-            signature = .init()
+        get throws {
+            let signature: Data
+
+            if let decoded = Data(base64Encoded: self.signature) {
+                signature = decoded
+            } else {
+                throw Error.failedToDecodeSignature(self.signature)
+            }
+
+            return .promotionalOffer(
+                offerID: self.identifier,
+                keyID: self.keyIdentifier,
+                nonce: self.nonce,
+                signature: signature,
+                timestamp: self.timestamp
+            )
         }
+    }
 
-        return .promotionalOffer(
-            offerID: self.identifier,
-            keyID: self.keyIdentifier,
-            nonce: self.nonce,
-            signature: signature,
-            timestamp: self.timestamp
-        )
+}
+
+// MARK: -
+
+extension PromotionalOffer.SignedData.Error: LocalizedError {
+
+    var errorDescription: String? {
+        switch self {
+        case let .failedToDecodeSignature(signature):
+            return "The signature generated by RevenueCat could not be decoded: \(signature)"
+        }
     }
 
 }

Tests/StoreKitUnitTests/PurchasesOrchestratorTests.swift

@@ -467,6 +467,33 @@ class PurchasesOrchestratorTests: StoreKitConfigTestCase {
         }
     }
 
+    @available(iOS 15.0, tvOS 15.0, watchOS 8.0, macOS 12.0, *)
+    func testPurchaseSK2PackageWithInvalidPromotionalOfferSignatureThrowsError() async throws {
+        try AvailabilityChecks.iOS15APIAvailableOrSkipTest()
+
+        self.customerInfoManager.stubbedCachedCustomerInfoResult = self.mockCustomerInfo
+        self.backend.stubbedPostReceiptResult = .success(self.mockCustomerInfo)
+
+        let product = try await self.fetchSk2Product()
+        let offer = PromotionalOffer.SignedData(
+            identifier: "identifier \(Int.random(in: 0..<1000))",
+            keyIdentifier: "key identifier \(Int.random(in: 0..<1000))",
+            nonce: .init(),
+            // This should be base64
+            signature: "signature \(Int.random(in: 0..<1000))",
+            timestamp: Int.random(in: 0..<1000)
+        )
+
+        do {
+            _ = try await orchestrator.purchase(sk2Product: product, promotionalOffer: offer)
+            XCTFail("Expected error")
+        } catch {
+            expect(error).to(matchError(ErrorCode.invalidPromotionalOfferError))
+            expect(error.localizedDescription)
+                .to(contain("The signature generated by RevenueCat could not be decoded: \(offer.signature)"))
+        }
+    }
+
     @available(iOS 15.0, tvOS 15.0, watchOS 8.0, macOS 12.0, *)
     func testPurchaseSK2PackageReturnsCustomerInfoForFailedTransaction() async throws {
         try AvailabilityChecks.iOS15APIAvailableOrSkipTest()

Tests/UnitTests/Purchasing/StoreKitAbstractions/PromotionalOfferTests.swift

@@ -32,25 +32,50 @@ class PromotionalOfferTests: TestCase {
     func testSK2PurchaseOption() throws {
         try AvailabilityChecks.iOS15APIAvailableOrSkipTest()
 
-        let option = Self.randomOffer.sk2PurchaseOption
+        let option = try Self.randomOffer.sk2PurchaseOption
         let expected: Product.PurchaseOption = .promotionalOffer(
             offerID: Self.randomOffer.identifier,
             keyID: Self.randomOffer.keyIdentifier,
             nonce: Self.randomOffer.nonce,
-            signature: Self.randomOffer.signature.asData,
+            // `Product.PurchaseOption` conforms to Equatable but it does not compare this
+            // The only way to validate this is correct is integration tests.
+            signature: Data(),
             timestamp: Self.randomOffer.timestamp
         )
 
         expect(option) == expected
     }
 
+    @available(iOS 15.0, tvOS 15.0, watchOS 8.0, macOS 12.0, *)
+    func testSK2PurchaseOptionWithInvalidSignatureThrows() throws {
+        try AvailabilityChecks.iOS15APIAvailableOrSkipTest()
+
+        do {
+            _ = try Self.invalidOffer.sk2PurchaseOption
+            fail("Expected error")
+        } catch {
+            expect(error).to(matchError(
+                PromotionalOffer.SignedData.Error
+                    .failedToDecodeSignature(Self.invalidOffer.signature)
+            ))
+        }
+    }
+
 }
 
 // MARK: - Private
 
 private extension PromotionalOfferTests {
 
     static let randomOffer: PromotionalOffer.SignedData = .init(
+        identifier: "identifier \(Int.random(in: 0..<1000))",
+        keyIdentifier: "key identifier \(Int.random(in: 0..<1000))",
+        nonce: .init(),
+        signature: "signature \(Int.random(in: 0..<1000))".asData.base64EncodedString(),
+        timestamp: Int.random(in: 0..<1000)
+    )
+
+    static let invalidOffer: PromotionalOffer.SignedData = .init(
         identifier: "identifier \(Int.random(in: 0..<1000))",
         keyIdentifier: "key identifier \(Int.random(in: 0..<1000))",
         nonce: .init(),