Use new PlatformDispatcher onError method if available (#109)

* Use new PlatformDispatcher onError method if available
* Updated Flutter Demo with more types of possible uncaught errors

Author: matux

rollbar_flutter/example/lib/main.dart

@@ -104,7 +104,7 @@ class MyHomePageState extends State<MyHomePage> {
 
     setState(() {
       if (++_counter % 2 == 0) {
-        throw ArgumentError('Unavoidable failure');
+        throw ArgumentError('Failed to increment counter');
       } else {
         Rollbar.drop(
           rollbar.Breadcrumb.log('Counter incremented to $_counter'),
@@ -113,6 +113,14 @@ class MyHomePageState extends State<MyHomePage> {
     });
   }
 
+  void asyncFailure() {
+    _asyncFailure(1).then((n) => log('$n ~/ 0 = ???'));
+  }
+
+  Future<int> _asyncFailure(int num) async {
+    return Future<int>.delayed(Duration(seconds: num), () => num ~/ 0);
+  }
+
   void setUser() {
     if (_userIsLoggedIn) {
       Rollbar.setUser(null);
@@ -133,10 +141,10 @@ class MyHomePageState extends State<MyHomePage> {
     });
   }
 
-  void divideByZero() {
-    Rollbar.drop(rollbar.Breadcrumb.log('Tapped divideByZero button'));
-    Rollbar.critical('About to divide by zero, this won\'t work!');
-    1 ~/ 0;
+  void throwError() {
+    Rollbar.drop(rollbar.Breadcrumb.log('Tapped throwError button'));
+    Rollbar.critical('About to throw an error!');
+    throw StateError('A state error occurred');
   }
 
   void crash() {
@@ -157,10 +165,6 @@ class MyHomePageState extends State<MyHomePage> {
         child: const Text('Call Faulty Method'),
       ),
       Text(_faultyMsg),
-      ElevatedButton(
-        onPressed: divideByZero,
-        child: const Text('Divide by zero'),
-      ),
       if (Platform.isIOS)
         ElevatedButton(
           onPressed: crash,
@@ -172,6 +176,15 @@ class MyHomePageState extends State<MyHomePage> {
         child: Text(_setUserText),
       ),
       const Divider(),
+      ElevatedButton(
+        onPressed: asyncFailure,
+        child: const Text('Async failure'),
+      ),
+      ElevatedButton(
+        onPressed: throwError,
+        child: const Text('Throw error'),
+      ),
+      const Divider(),
       const Text('Times you have pushed the plus button:'),
       Text(
         '$_counter',

rollbar_flutter/lib/src/flutter_error.dart renamed to rollbar_flutter/lib/src/hooks/flutter_hook.dart

@@ -1,15 +1,17 @@
 import 'package:flutter/foundation.dart';
+import 'package:meta/meta.dart';
 
 import 'package:rollbar_common/rollbar_common.dart';
 import 'package:rollbar_dart/rollbar.dart';
 
-import 'extension/diagnostics.dart';
+import '../extension/diagnostics.dart';
+import 'hook.dart';
 
-extension RollbarFlutterError on FlutterError {
-  /// Called whenever the Flutter framework catches an error.
-  ///
-  /// The default behavior is to call [presentError].
-  static void onError(FlutterErrorDetails error) {
+@sealed
+class FlutterHook implements Hook {
+  FlutterExceptionHandler? _originalOnError;
+
+  void onError(FlutterErrorDetails error) {
     if (!error.silent) {
       Rollbar.drop(
         Breadcrumb.error(
@@ -27,6 +29,22 @@ extension RollbarFlutterError on FlutterError {
       Rollbar.error(error.exception, error.stack ?? StackTrace.empty);
     }
 
-    FlutterError.presentError(error);
+    if (_originalOnError != null) {
+      _originalOnError!(error);
+    }
+  }
+
+  @override
+  void install(_) {
+    _originalOnError = FlutterError.onError;
+    FlutterError.onError = onError;
+  }
+
+  @override
+  void uninstall() {
+    if (FlutterError.onError == onError) {
+      FlutterError.onError = _originalOnError;
+      _originalOnError = null;
+    }
   }
 }

rollbar_flutter/lib/src/hooks/hook.dart

@@ -0,0 +1,9 @@
+import 'dart:async';
+
+import 'package:rollbar_dart/rollbar.dart';
+
+abstract class Hook {
+  FutureOr<void> install(final Config config);
+
+  FutureOr<void> uninstall();
+}

rollbar_flutter/lib/src/hooks/platform_hook.dart

@@ -0,0 +1,34 @@
+import 'dart:ui';
+import 'package:rollbar_dart/rollbar.dart';
+import 'hook.dart';
+
+class PlatformHook implements Hook {
+  ErrorCallback? _originalOnError;
+  PlatformDispatcher? _platformDispatcher;
+
+  bool onError(Object exception, StackTrace stackTrace) {
+    Rollbar.error(exception, stackTrace);
+
+    if (_originalOnError != null) {
+      return _originalOnError!(exception, stackTrace);
+    }
+
+    return false;
+  }
+
+  @override
+  void install(_) {
+    _platformDispatcher = PlatformDispatcher.instance;
+    _originalOnError = _platformDispatcher?.onError;
+    _platformDispatcher?.onError = onError;
+  }
+
+  @override
+  void uninstall() {
+    if (_platformDispatcher?.onError == onError) {
+      _platformDispatcher?.onError = _originalOnError;
+      _originalOnError = null;
+      _platformDispatcher = null;
+    }
+  }
+}

rollbar_flutter/lib/src/rollbar.dart

@@ -7,7 +7,9 @@ import 'package:meta/meta.dart';
 
 import 'package:rollbar_dart/rollbar.dart';
 
-import 'flutter_error.dart';
+import 'hooks/hook.dart';
+import 'hooks/flutter_hook.dart';
+import 'hooks/platform_hook.dart';
 import 'platform_transformer.dart';
 
 extension _Methods on MethodChannel {
@@ -22,48 +24,54 @@ extension _Methods on MethodChannel {
 typedef RollbarClosure = FutureOr<void> Function();
 
 @sealed
+@immutable
 class RollbarFlutter {
   static const _platform = MethodChannel('com.rollbar.flutter');
 
-  RollbarFlutter._();
+  const RollbarFlutter._();
 
   static Future<void> run(
     Config config,
     RollbarClosure appRunner,
   ) async {
     if (!config.handleUncaughtErrors) {
-      WidgetsFlutterBinding.ensureInitialized();
-
-      await _run(config, appRunner, null);
-
-      return;
+      await _run(config, appRunner);
+    } else if (requiresCustomZone) {
+      await runZonedGuarded(
+          () async => await _run(config, appRunner, [FlutterHook()]),
+          Rollbar.error);
+    } else {
+      await _run(config, appRunner, [FlutterHook(), PlatformHook()]);
     }
-
-    await runZonedGuarded(() async {
-      WidgetsFlutterBinding.ensureInitialized();
-
-      await _run(config, appRunner, RollbarFlutterError.onError);
-    }, (exception, stackTrace) {
-      Rollbar.error(exception, stackTrace);
-    });
   }
 
   static Future<void> _run(
     Config config,
-    RollbarClosure appRunner,
-    FlutterExceptionHandler? onError,
-  ) async {
+    RollbarClosure appRunner, [
+    List<Hook> hooks = const [],
+  ]) async {
+    WidgetsFlutterBinding.ensureInitialized();
+
     await Rollbar.run(config.copyWith(
       framework: 'flutter',
       persistencePath: await _platform.persistencePath,
       transformer: (_) => PlatformTransformer(),
     ));
 
-    if (onError != null) {
-      FlutterError.onError = onError;
+    for (final hook in hooks) {
+      await hook.install(config);
     }
 
     await _platform.initialize(config: config);
     await appRunner();
   }
+
+  static bool get requiresCustomZone {
+    try {
+      (PlatformDispatcher.instance as dynamic)?.onError;
+      return false;
+    } on NoSuchMethodError {
+      return true;
+    }
+  }
 }