fix: Clean up error codes

analysis_options.yaml

@@ -4,4 +4,5 @@ linter:
   rules:
     - combinators_ordering
     - require_trailing_commas
-    - unnecessary_library_directive
+    - unnecessary_library_directive
+    - prefer_single_quotes

android/src/main/kotlin/dev/steenbakker/mobile_scanner/MobileScanner.kt

@@ -120,12 +120,7 @@ class MobileScanner(
                 }
 
                 if (!returnImage) {
-                    mobileScannerCallback(
-                        barcodeMap,
-                        null,
-                        null,
-                        null
-                    )
+                    mobileScannerCallback(barcodeMap, null, null, null)
                     return@addOnSuccessListener
                 }
 

android/src/main/kotlin/dev/steenbakker/mobile_scanner/objects/MobileScannerErrorCodes.kt

@@ -0,0 +1,25 @@
+package dev.steenbakker.mobile_scanner.objects
+
+class MobileScannerErrorCodes {
+    companion object {
+        const val ALREADY_STARTED_ERROR = "MOBILE_SCANNER_ALREADY_STARTED_ERROR"
+        const val ALREADY_STARTED_ERROR_MESSAGE = "The scanner was already started."
+        // The error code 'BARCODE_ERROR' does not have an error message,
+        // because it uses the error message from the underlying error.
+        const val BARCODE_ERROR = "MOBILE_SCANNER_BARCODE_ERROR"
+        // The error code 'CAMERA_ACCESS_DENIED' does not have an error message,
+        // because it is used for a boolean result.
+        const val CAMERA_ACCESS_DENIED = "MOBILE_SCANNER_CAMERA_PERMISSION_DENIED"
+        const val CAMERA_ERROR = "MOBILE_SCANNER_CAMERA_ERROR"
+        const val CAMERA_ERROR_MESSAGE = "An error occurred when opening the camera."
+        const val CAMERA_PERMISSIONS_REQUEST_ONGOING = "MOBILE_SCANNER_CAMERA_PERMISSION_REQUEST_PENDING"
+        const val CAMERA_PERMISSIONS_REQUEST_ONGOING_MESSAGE = "Another request is ongoing and multiple requests cannot be handled at once."
+        const val GENERIC_ERROR = "MOBILE_SCANNER_GENERIC_ERROR"
+        const val GENERIC_ERROR_MESSAGE = "An unknown error occurred."
+        const val INVALID_ZOOM_SCALE_ERROR_MESSAGE = "The zoom scale should be between 0 and 1 (both inclusive)"
+        const val NO_CAMERA_ERROR = "MOBILE_SCANNER_NO_CAMERA_ERROR"
+        const val NO_CAMERA_ERROR_MESSAGE = "No cameras available."
+        const val SET_SCALE_WHEN_STOPPED_ERROR = "MOBILE_SCANNER_SET_SCALE_WHEN_STOPPED_ERROR"
+        const val SET_SCALE_WHEN_STOPPED_ERROR_MESSAGE = "The zoom scale cannot be changed when the camera is stopped."
+    }
+}

example/lib/barcode_scanner_controller.dart

@@ -60,7 +60,7 @@ class _BarcodeScannerWithControllerState
 
   @override
   void didChangeAppLifecycleState(AppLifecycleState state) {
-    if (!controller.value.isInitialized) {
+    if (!controller.value.hasCameraPermission) {
       return;
     }
 

ios/Classes/MobileScannerError.swift

@@ -6,6 +6,12 @@
 //
 import Foundation
 
+// TODO: decide if we should keep or discard this enum
+// When merging the iOS / MacOS implementations we should either keep the enum or remove it
+
+// This enum is a bit of a leftover from older parts of the iOS implementation.
+// It is used by the handler that throws these error codes,
+// while the plugin class intercepts these and converts them to `FlutterError()`s.
 enum MobileScannerError: Error {
     case noCamera
     case alreadyStarted

ios/Classes/MobileScannerErrorCodes.swift

@@ -0,0 +1,33 @@
+//
+//  MobileScannerErrorCodes.swift
+//  mobile_scanner
+//
+//  Created by Navaron Bracke on 28/05/2024.
+//
+
+import Foundation
+
+/// This struct defines the error codes and error messages for MobileScanner errors.
+///
+/// These are used by `FlutterError` as error code and error message.
+/// 
+/// This struct should not be confused with `MobileScannerError`,
+/// which is an implementation detail for the iOS implementation.
+struct MobileScannerErrorCodes {
+    static let ALREADY_STARTED_ERROR = "MOBILE_SCANNER_ALREADY_STARTED_ERROR"
+    static let ALREADY_STARTED_ERROR_MESSAGE = "The scanner was already started."
+    // The error code 'BARCODE_ERROR' does not have an error message,
+    // because it uses the error message from the undelying error.
+    static let BARCODE_ERROR = "MOBILE_SCANNER_BARCODE_ERROR"
+    // The error code 'CAMERA_ERROR' does not have an error message,
+    // because it uses the error message from the underlying error.    
+    static let CAMERA_ERROR = "MOBILE_SCANNER_CAMERA_ERROR"
+    static let GENERIC_ERROR = "MOBILE_SCANNER_GENERIC_ERROR"
+    static let GENERIC_ERROR_MESSAGE = "An unknown error occurred."
+    // This message is used with the 'GENERIC_ERROR' error code.
+    static let INVALID_ZOOM_SCALE_ERROR_MESSAGE = "The zoom scale should be between 0 and 1 (both inclusive)"
+    static let NO_CAMERA_ERROR = "MOBILE_SCANNER_NO_CAMERA_ERROR"
+    static let NO_CAMERA_ERROR_MESSAGE = "No cameras available."
+    static let SET_SCALE_WHEN_STOPPED_ERROR = "MOBILE_SCANNER_SET_SCALE_WHEN_STOPPED_ERROR"
+    static let SET_SCALE_WHEN_STOPPED_ERROR_MESSAGE = "The zoom scale cannot be changed when the camera is stopped."
+}

ios/Classes/MobileScannerPlugin.swift

@@ -258,9 +258,7 @@ public class MobileScannerPlugin: NSObject, FlutterPlugin {
         let uiImage = UIImage(contentsOfFile: (call.arguments as! Dictionary<String, Any?>)["filePath"] as? String ?? "")
 
         if (uiImage == nil) {
-            result(FlutterError(code: "MobileScanner",
-                                message: "No image found in analyzeImage!",
-                                details: nil))
+            result(nil)
             return
         }
 

lib/src/enums/mobile_scanner_error_code.dart

@@ -1,3 +1,4 @@
+import 'package:flutter/services.dart';
 import 'package:mobile_scanner/src/mobile_scanner_controller.dart';
 
 /// This enum defines the different error codes for the mobile scanner.
@@ -24,5 +25,25 @@ enum MobileScannerErrorCode {
   permissionDenied,
 
   /// Scanning is unsupported on the current device.
-  unsupported,
+  unsupported;
+
+  /// Convert the given [PlatformException.code] to a [MobileScannerErrorCode].
+  factory MobileScannerErrorCode.fromPlatformException(
+    PlatformException exception,
+  ) {
+    // The following error code mapping should be kept in sync with their native counterparts.
+    // These are located in `MobileScannerErrorCodes.kt` and `MobileScannerErrorCodes.swift`.
+    return switch (exception.code) {
+      // In case the scanner was already started, report the right error code.
+      // If the scanner is already starting,
+      // this error code is a signal to the controller to just ignore the attempt.
+      'MOBILE_SCANNER_ALREADY_STARTED_ERROR' =>
+        MobileScannerErrorCode.controllerAlreadyInitialized,
+      // In case no cameras are available, using the scanner is not supported.
+      'MOBILE_SCANNER_NO_CAMERA_ERROR' => MobileScannerErrorCode.unsupported,
+      'MOBILE_SCANNER_CAMERA_PERMISSION_DENIED' =>
+        MobileScannerErrorCode.permissionDenied,
+      _ => MobileScannerErrorCode.genericError,
+    };
+  }
 }

lib/src/method_channel/mobile_scanner_method_channel.dart

@@ -187,8 +187,7 @@ class MethodChannelMobileScanner extends MobileScannerPlatform {
       throw const MobileScannerException(
         errorCode: MobileScannerErrorCode.controllerAlreadyInitialized,
         errorDetails: MobileScannerErrorDetails(
-          message:
-              'The scanner was already started. Call stop() before calling start() again.',
+          message: 'The scanner was already started.',
         ),
       );
     }
@@ -204,7 +203,7 @@ class MethodChannelMobileScanner extends MobileScannerPlatform {
       );
     } on PlatformException catch (error) {
       throw MobileScannerException(
-        errorCode: MobileScannerErrorCode.genericError,
+        errorCode: MobileScannerErrorCode.fromPlatformException(error),
         errorDetails: MobileScannerErrorDetails(
           code: error.code,
           details: error.details as Object?,
@@ -240,17 +239,13 @@ class MethodChannelMobileScanner extends MobileScannerPlatform {
       startResult['currentTorchState'] as int? ?? -1,
     );
 
-    final Map<Object?, Object?>? sizeInfo =
-        startResult['size'] as Map<Object?, Object?>?;
-    final double? width = sizeInfo?['width'] as double?;
-    final double? height = sizeInfo?['height'] as double?;
-
     final Size size;
 
-    if (width == null || height == null) {
-      size = Size.zero;
-    } else {
+    if (startResult['size']
+        case {'width': final double width, 'height': final double height}) {
       size = Size(width, height);
+    } else {
+      size = Size.zero;
     }
 
     return MobileScannerViewAttributes(

lib/src/mobile_scanner.dart

@@ -281,8 +281,7 @@ class _MobileScannerState extends State<MobileScanner>
 
   @override
   void didChangeAppLifecycleState(AppLifecycleState state) {
-    if (widget.controller != null) return;
-    if (!controller.value.isInitialized) {
+    if (widget.controller != null || !controller.value.hasCameraPermission) {
       return;
     }
 

lib/src/mobile_scanner_exception.dart

@@ -1,6 +1,6 @@
 import 'package:mobile_scanner/src/enums/mobile_scanner_error_code.dart';
 
-/// This class represents an exception thrown by the mobile scanner.
+/// This class represents an exception thrown by the [MobileScannerController].
 class MobileScannerException implements Exception {
   const MobileScannerException({
     required this.errorCode,
@@ -16,9 +16,9 @@ class MobileScannerException implements Exception {
   @override
   String toString() {
     if (errorDetails != null && errorDetails?.message != null) {
-      return "MobileScannerException: code ${errorCode.name}, message: ${errorDetails?.message}";
+      return 'MobileScannerException(${errorCode.name}, ${errorDetails?.message})';
     }
-    return "MobileScannerException: ${errorCode.name}";
+    return 'MobileScannerException(${errorCode.name})';
   }
 }
 
@@ -46,3 +46,22 @@ class MobileScannerErrorDetails {
 /// This exception type is only used internally,
 /// and is not part of the public API.
 class PermissionRequestPendingException implements Exception {}
+
+/// This class represents an exception thrown by the [MobileScannerController]
+/// when a barcode scanning error occurs when processing an input frame.
+class MobileScannerBarcodeException implements Exception {
+  /// Creates a new [MobileScannerBarcodeException] with the given error message.
+  const MobileScannerBarcodeException(this.message);
+
+  /// The error message of the exception.
+  final String? message;
+
+  @override
+  String toString() {
+    if (message?.isNotEmpty ?? false) {
+      return 'MobileScannerBarcodeException($message)';
+    }
+
+    return 'MobileScannerBarcodeException(Could not detect a barcode in the input image.)';
+  }
+}

lib/src/objects/mobile_scanner_state.dart

@@ -1,6 +1,7 @@
 import 'dart:ui';
 
 import 'package:mobile_scanner/src/enums/camera_facing.dart';
+import 'package:mobile_scanner/src/enums/mobile_scanner_error_code.dart';
 import 'package:mobile_scanner/src/enums/torch_state.dart';
 import 'package:mobile_scanner/src/mobile_scanner_exception.dart';
 
@@ -43,7 +44,8 @@ class MobileScannerState {
 
   /// Whether the mobile scanner has initialized successfully.
   ///
-  /// This is `true` if the camera is ready to be used.
+  /// This does not indicate that the camera permission was granted.
+  /// To check if the camera permission was granted, use [hasCameraPermission].
   final bool isInitialized;
 
   /// Whether the mobile scanner is currently running.
@@ -60,6 +62,12 @@ class MobileScannerState {
   /// The current zoom scale of the camera.
   final double zoomScale;
 
+  /// Whether permission to access the camera was granted.
+  bool get hasCameraPermission {
+    return isInitialized &&
+        error?.errorCode != MobileScannerErrorCode.permissionDenied;
+  }
+
   /// Create a copy of this state with the given parameters.
   MobileScannerState copyWith({
     int? availableCameras,

macos/mobile_scanner/Sources/mobile_scanner/MobileScannerErrorCodes.swift

@@ -0,0 +1,21 @@
+//
+//  MobileScannerErrorCodes.swift
+//  mobile_scanner
+//
+//  Created by Navaron Bracke on 27/05/2024.
+//
+
+import Foundation
+
+struct MobileScannerErrorCodes {
+    static let ALREADY_STARTED_ERROR = "MOBILE_SCANNER_ALREADY_STARTED_ERROR"
+    static let ALREADY_STARTED_ERROR_MESSAGE = "The scanner was already started."
+    // The error code 'BARCODE_ERROR' does not have an error message,
+    // because it uses the error message from the undelying error.
+    static let BARCODE_ERROR = "MOBILE_SCANNER_BARCODE_ERROR"
+    // The error code 'CAMERA_ERROR' does not have an error message,
+    // because it uses the error message from the underlying error.       
+    static let CAMERA_ERROR = "MOBILE_SCANNER_CAMERA_ERROR"
+    static let NO_CAMERA_ERROR = "MOBILE_SCANNER_NO_CAMERA_ERROR"
+    static let NO_CAMERA_ERROR_MESSAGE = "No cameras available."
+}

macos/mobile_scanner/Sources/mobile_scanner/MobileScannerPlugin.swift

@@ -273,7 +273,6 @@ public class MobileScannerPlugin: NSObject, FlutterPlugin, FlutterStreamHandler,
 
         let argReader = MapArgumentReader(call.arguments as? [String: Any])
 
-        // let ratio: Int = argReader.int(key: "ratio")
         let torch:Bool = argReader.bool(key: "torch") ?? false
         let facing:Int = argReader.int(key: "facing") ?? 1
         let speed:Int = argReader.int(key: "speed") ?? 0
@@ -327,7 +326,6 @@ public class MobileScannerPlugin: NSObject, FlutterPlugin, FlutterStreamHandler,
         videoOutput.setSampleBufferDelegate(self, queue: DispatchQueue.main)
         captureSession!.addOutput(videoOutput)
         for connection in videoOutput.connections {
-            // connection.videoOrientation = .portrait
             if position == .front && connection.isVideoMirroringSupported {
                 connection.isVideoMirrored = true
             }
@@ -459,20 +457,14 @@ public class MobileScannerPlugin: NSObject, FlutterPlugin, FlutterStreamHandler,
         let symbologies:[VNBarcodeSymbology] = argReader.toSymbology()
 
         guard let filePath: String = argReader.string(key: "filePath") else {
-            // TODO: fix error code
-            result(FlutterError(code: "MobileScanner",
-                                message: "No image found in analyzeImage!",
-                                details: nil))
+            result(nil)
             return
         }
 
         let fileUrl = URL(fileURLWithPath: filePath)
 
         guard let ciImage = CIImage(contentsOf: fileUrl) else {
-            // TODO: fix error code
-            result(FlutterError(code: "MobileScanner",
-                                message: "No image found in analyzeImage!",
-                                details: nil))
+            result(nil)
             return
         }