Merge pull request #186 from AvdLee/feature/better-errors

Parse JSON error response

Example/Shared/AppsListView.swift

@@ -26,8 +26,14 @@ struct AppsListView: View {
                     .opacity(viewModel.apps.isEmpty ? 1.0 : 0.0)
             }.navigationTitle("List of Apps")
                 .toolbar {
-                    Button("Refresh") {
-                        viewModel.loadApps()
+                    ToolbarItemGroup(placement: .bottomBar) {
+                        Button("Refresh") {
+                            viewModel.loadApps()
+                        }
+
+                        Button("Fail") {
+                            viewModel.loadFailureExample()
+                        }
                     }
                 }
         }.onAppear {
@@ -65,7 +71,31 @@ final class AppsListViewModel: ObservableObject {
                 let apps = try await self.provider.request(request).data
                 await self.updateApps(to: apps)
             } catch {
-                print("Something went wrong fetching the apps: \(error)")
+                print("Something went wrong fetching the apps: \(error.localizedDescription)")
+            }
+        }
+    }
+
+    /// This demonstrates a failing example and how you can catch error details.
+    func loadFailureExample() {
+        Task.detached {
+            let requestWithError = APIEndpoint
+                .v1
+                .builds
+                .id("app.appId")
+                .get()
+
+            do {
+                print(try await self.provider.request(requestWithError).data)
+            } catch APIProvider.Error.requestFailure(let statusCode, let errorResponse, _) {
+                print("Request failed with statuscode: \(statusCode) and the following errors:")
+                errorResponse?.errors?.forEach({ error in
+                    print("Error code: \(error.code)")
+                    print("Error title: \(error.title)")
+                    print("Error detail: \(error.detail)")
+                })
+            } catch {
+                print("Something went wrong fetching the apps: \(error.localizedDescription)")
             }
         }
     }

README.md

@@ -65,6 +65,27 @@ let apps = try await self.provider.request(request).data
 print("Did fetch \(apps.count) apps")
 ```
 
+### Handling errors
+Whenever an error is returned from a request, you can get the details by catching the error as follows:
+
+```swift
+do {
+    print(try await self.provider.request(requestWithError).data)
+} catch APIProvider.Error.requestFailure(let statusCode, let errorResponse, _) {
+    print("Request failed with statuscode: \(statusCode) and the following errors:")
+    errorResponse?.errors?.forEach({ error in
+        print("Error code: \(error.code)")
+        print("Error title: \(error.title)")
+        print("Error detail: \(error.detail)")
+    })
+} catch {
+    print("Something went wrong fetching the apps: \(error.localizedDescription)")
+}
+```
+
+The error title and detail should help you solve the failure.
+For more info regarding errors, see: [Parsing the Error Response Code](https://developer.apple.com/documentation/appstoreconnectapi/interpreting_and_handling_errors/parsing_the_error_response_code) as documented by Apple.
+
 ## Installation
 
 ### Swift Package Manager

Sources/APIProvider.swift

@@ -38,7 +38,7 @@ public final class APIProvider {
     public enum Error: Swift.Error, CustomDebugStringConvertible, LocalizedError {
         case requestGeneration
         case unknownResponseType
-        case requestFailure(StatusCode, Data?, URL?)
+        case requestFailure(StatusCode, ErrorResponse?, URL?)
         case decodingError(Swift.Error, Data)
         case downloadError
         case dateDecodingError(String)
@@ -47,17 +47,17 @@ public final class APIProvider {
         public var errorDescription: String? {
             debugDescription
         }
-        
+
         public var debugDescription: String {
             switch self {
             case .requestGeneration:
                 return "Failed to generate request."
             case .unknownResponseType:
                 return "Unknown response type."
-            case .requestFailure(let statusCode, let data, let url):
+            case .requestFailure(let statusCode, let errorResponse, let url):
                 let url = url?.absoluteString ?? ""
-                if let data = data, let response = String(data: data, encoding: .utf8) {
-                    return "Request \(url) failed with status code \(statusCode) and response \(response))."
+                if let errorResponse = errorResponse {
+                    return "Request \(url) failed with status code \(statusCode). \(errorResponse))."
                 }
                 return "Request \(url) failed with status code \(statusCode)."
             case .decodingError(let error, let data):
@@ -219,7 +219,7 @@ private extension APIProvider {
         switch result {
         case .success(let response):
             guard let data = response.data, 200..<300 ~= response.statusCode else {
-                return .failure(Error.requestFailure(response.statusCode, response.data, response.requestURL))
+                return .failure(Error.requestFailure(response.statusCode, response.errorResponse, response.requestURL))
             }
 
             if let data = data as? T {
@@ -245,7 +245,7 @@ private extension APIProvider {
         switch result {
         case .success(let response):
             guard 200..<300 ~= response.statusCode else {
-                return .failure(Error.requestFailure(response.statusCode, response.data, response.requestURL))
+                return .failure(Error.requestFailure(response.statusCode, response.errorResponse, response.requestURL))
             }
 
             return .success(())
@@ -262,7 +262,7 @@ private extension APIProvider {
         switch result {
         case .success(let response):
             guard 200..<300 ~= response.statusCode else {
-                return .failure(Error.requestFailure(response.statusCode, nil, response.requestURL))
+                return .failure(Error.requestFailure(response.statusCode, response.errorResponse, response.requestURL))
             }
             if let data = response.data {
                 return .success(data)

Sources/Extensions/ErrorResponseExtensions.swift

@@ -0,0 +1,22 @@
+//
+//  ErrorResponseExtensions.swift
+//  
+//
+//  Created by Antoine van der Lee on 29/07/2022.
+//
+
+import Foundation
+
+extension ErrorResponse: CustomStringConvertible {
+    public var description: String {
+        var errorString = "Related response error(s):"
+        errors?.forEach({ error in
+            errorString.append("""
+        \n\nThe request failed with response code \(error.status) \(error.code)
+
+        \(error.title). \(error.detail)
+        """)
+        })
+        return errorString
+    }
+}

Sources/RequestExecutor.swift

@@ -14,11 +14,18 @@ public struct Response<T> {
     public let requestURL: URL?
     public let statusCode: Int
     public let data: T?
+    public let errorResponse: ErrorResponse?
 
     public init(requestURL: URL?, statusCode: StatusCode, data: T?) {
         self.requestURL = requestURL
         self.statusCode = statusCode
         self.data = data
+
+        if let data = data as? Data {
+            self.errorResponse = try? APIProvider.jsonDecoder.decode(ErrorResponse.self, from: data)
+        } else {
+            self.errorResponse = nil
+        }
     }
 }
 

Tests/APIProviderTests.swift

@@ -54,9 +54,19 @@ final class APIProviderTests: XCTestCase {
         }
     }
 
-    func testRequestExecutionErrorResponse() {
+    func testRequestExecutionErrorResponse() throws {
         let expectedURL = URL(string: "https://api.appstoreconnect.apple.com")!
-        let response = Response<Data>(requestURL: expectedURL, statusCode: 500, data: nil)
+        let errorResponse = ErrorResponse(errors: [
+            .init(
+                id: UUID().uuidString,
+                status: "404",
+                code: "NOT_FOUND",
+                title: "The specified resource does not exist",
+                detail: "There is no resource of type 'builds' with id 'app.appId'"
+            )
+        ])
+        let responseData = try JSONEncoder().encode(errorResponse)
+        let response = Response<Data>(requestURL: expectedURL, statusCode: 404, data: responseData)
         let mockRequestExecutor = MockRequestExecutor(expectedResponse: Result.success(response))
         let apiProvider = APIProvider(configuration: configuration, requestExecutor: mockRequestExecutor)
 
@@ -66,13 +76,20 @@ final class APIProviderTests: XCTestCase {
             XCTAssertNotNil(result.error)
             guard
                 let error = result.error as? APIProvider.Error,
-                case let APIProvider.Error.requestFailure(statusCode, data, url) = error else {
+                case let APIProvider.Error.requestFailure(statusCode, errorResponse, url) = error else {
                 XCTFail("We expect a requestFailure error")
                 return
             }
-            XCTAssertNil(data)
-            XCTAssertEqual(statusCode, 500)
+            XCTAssertNotNil(errorResponse)
+            XCTAssertEqual(statusCode, 404)
             XCTAssertEqual(url?.absoluteString, expectedURL.absoluteString)
+            XCTAssertEqual(error.localizedDescription, """
+            Request https://api.appstoreconnect.apple.com failed with status code 404. Related response error(s):
+
+            The request failed with response code 404 NOT_FOUND
+
+            The specified resource does not exist. There is no resource of type 'builds' with id 'app.appId').
+            """)
         }
     }