Fixes crash when sending undefined message via javascript channel

Author: LinXunFeng

packages/webview_flutter/webview_flutter_wkwebview/CHANGELOG.md

@@ -1,3 +1,7 @@
+## 3.18.4
+
+* Fixes crash when sending undefined message via javascript channel.
+
 ## 3.18.3
 
 * Fixes crash where the native `AuthenticationChallengeResponse` could not be found for auth

packages/webview_flutter/webview_flutter_wkwebview/example/integration_test/webview_flutter_test.dart

@@ -278,6 +278,47 @@ Future<void> main() async {
     await expectLater(channelCompleter.future, completion('hello'));
   });
 
+  testWidgets('JavascriptChannel can receive undefined',
+      (WidgetTester tester) async {
+    final Completer<void> pageFinished = Completer<void>();
+    final PlatformWebViewController controller = PlatformWebViewController(
+      const PlatformWebViewControllerCreationParams(),
+    );
+    unawaited(controller.setJavaScriptMode(JavaScriptMode.unrestricted));
+    final PlatformNavigationDelegate delegate = PlatformNavigationDelegate(
+      const PlatformNavigationDelegateCreationParams(),
+    );
+    unawaited(delegate.setOnPageFinished((_) => pageFinished.complete()));
+    unawaited(controller.setPlatformNavigationDelegate(delegate));
+
+    final Completer<String> channelCompleter = Completer<String>();
+    await controller.addJavaScriptChannel(
+      JavaScriptChannelParams(
+        name: 'Channel',
+        onMessageReceived: (JavaScriptMessage message) {
+          channelCompleter.complete(message.message);
+        },
+      ),
+    );
+
+    await controller.loadHtmlString(
+      'data:text/html;charset=utf-8;base64,PCFET0NUWVBFIGh0bWw+',
+    );
+
+    await tester.pumpWidget(Builder(
+      builder: (BuildContext context) {
+        return PlatformWebViewWidget(
+          PlatformWebViewWidgetCreationParams(controller: controller),
+        ).build(context);
+      },
+    ));
+
+    await pageFinished.future;
+
+    await controller.runJavaScript('Channel.postMessage(undefined);');
+    await expectLater(channelCompleter.future, completion(''));
+  });
+
   testWidgets('resize webview', (WidgetTester tester) async {
     final Completer<void> buttonTapResizeCompleter = Completer<void>();
     final Completer<void> onPageFinished = Completer<void>();

packages/webview_flutter/webview_flutter_wkwebview/lib/src/common/weak_reference_utils.dart

@@ -18,7 +18,7 @@
 ///       ) {
 ///         weakReference.target?.onJavascriptChannelMessage(
 ///           message.name,
-///           message.body!.toString(),
+///           message.body?.toString() ?? '',
 ///         );
 ///       };
 ///     },

packages/webview_flutter/webview_flutter_wkwebview/lib/src/webkit_webview_controller.dart

@@ -906,7 +906,7 @@ class WebKitJavaScriptChannelParams extends JavaScriptChannelParams {
               return (_, __, WKScriptMessage message) {
                 if (weakReference.target != null) {
                   weakReference.target!(
-                    JavaScriptMessage(message: message.body!.toString()),
+                    JavaScriptMessage(message: message.body?.toString() ?? ''),
                   );
                 }
               };

packages/webview_flutter/webview_flutter_wkwebview/pubspec.yaml

@@ -2,7 +2,7 @@ name: webview_flutter_wkwebview
 description: A Flutter plugin that provides a WebView widget based on Apple's WKWebView control.
 repository: https://github.com/flutter/packages/tree/main/packages/webview_flutter/webview_flutter_wkwebview
 issue_tracker: https://github.com/flutter/flutter/issues?q=is%3Aissue+is%3Aopen+label%3A%22p%3A+webview%22
-version: 3.18.3
+version: 3.18.4
 
 environment:
   sdk: ^3.5.0