add unit test cases

Author: 5d

AmplifyPlugins/API/Sources/AWSAPIPlugin/Operation/AWSGraphQLSubscriptionTaskRunner.swift

@@ -379,14 +379,14 @@ fileprivate func toAPIError<R: Decodable>(_ errors: [Error], type: R.Type) -> AP
     }
 
 #if swift(<5.8)
-    if let errors = castArray(errors, withElementType: AppSyncRealTimeRequest.Error.self) {
+    if let errors = errors.cast(to: AppSyncRealTimeRequest.Error.self) {
         let hasAuthorizationError = errors.contains(where: { $0 == .unauthorized})
         return APIError.operationError(
             errorDescription(hasAuthorizationError),
             "",
             errors.first
         )
-    } else if let errors = castArray(errors, withElementType: GraphQLError.self) {
+    } else if let errors = errors.cast(to: GraphQLError.self) {
         let hasAuthorizationError = errors.map(\.extensions)
             .compactMap { $0.flatMap { $0["errorType"]?.stringValue } }
             .contains(where: { AppSyncErrorType($0) == .unauthorized })
@@ -429,14 +429,3 @@ fileprivate func toAPIError<R: Decodable>(_ errors: [Error], type: R.Type) -> AP
     }
 #endif
 }
-
-#if swift(<5.8)
-fileprivate func castArray<T>(_ arr: Array<Any>, withElementType: T.Type) -> [T]? {
-    arr.reduce([]) { result, ele in
-        if let result, let ele = ele as? T {
-            return result + [ele]
-        }
-        return nil
-    }
-}
-#endif

AmplifyPlugins/API/Sources/AWSAPIPlugin/Support/Utils/Array+Error+TypeCast.swift

@@ -0,0 +1,21 @@
+//
+// Copyright Amazon.com Inc. or its affiliates.
+// All Rights Reserved.
+//
+// SPDX-License-Identifier: Apache-2.0
+//
+
+
+import Foundation
+
+@_spi(AmplifyAPI)
+extension Array where Element == Error {
+    func cast<T>(to type: T.Type) -> [T]? {
+        self.reduce([]) { partialResult, ele in
+            if let partialResult, let ele = ele as? T {
+                return partialResult + [ele]
+            }
+            return nil
+        }
+    }
+}

AmplifyPlugins/API/Tests/AWSAPIPluginTests/Support/Utils/Array+Error+TypeCastTests.swift

@@ -0,0 +1,48 @@
+//
+// Copyright Amazon.com Inc. or its affiliates.
+// All Rights Reserved.
+//
+// SPDX-License-Identifier: Apache-2.0
+//
+
+
+import XCTest
+@testable @_spi(AmplifyAPI) import AWSAPIPlugin
+
+class ArrayWithErrorElementExtensionTests: XCTestCase {
+
+
+
+    func testCast_toCorrectErrorType_returnCastedErrorType() {
+        let errors: [Error] = [
+            Error1(), Error1(), Error1()
+        ]
+
+        let error1s = errors.cast(to: Error1.self)
+        XCTAssertNotNil(error1s)
+        XCTAssertTrue(!error1s!.isEmpty)
+        XCTAssertEqual(errors.count, error1s!.count)
+    }
+
+    func testCast_toWrongErrorType_returnNil() {
+        let errors: [Error] = [
+            Error1(), Error1(), Error1()
+        ]
+
+        let error2s = errors.cast(to: Error2.self)
+        XCTAssertNil(error2s)
+    }
+
+    func testCast_partiallyToWrongErrorType_returnNil() {
+        let errors: [Error] = [
+            Error2(), Error2(), Error1()
+        ]
+
+        let error2s = errors.cast(to: Error2.self)
+        XCTAssertNil(error2s)
+    }
+
+    struct Error1: Error { }
+
+    struct Error2: Error { }
+}