From 6abb6746eb1a532edf90eddb7b35d317586f8806 Mon Sep 17 00:00:00 2001
From: LinXunFeng <linxunfeng@yeah.net>
Date: Tue, 4 Mar 2025 11:13:59 +0800
Subject: [PATCH 01/10] Fixes crash when sending undefined message via
 javascript channel

---
 .../webview_flutter_wkwebview/CHANGELOG.md    |  4 ++
 .../webview_flutter_test.dart                 | 41 +++++++++++++++++++
 .../lib/src/common/weak_reference_utils.dart  |  2 +-
 .../lib/src/webkit_webview_controller.dart    |  2 +-
 .../webview_flutter_wkwebview/pubspec.yaml    |  2 +-
 5 files changed, 48 insertions(+), 3 deletions(-)

diff --git a/packages/webview_flutter/webview_flutter_wkwebview/CHANGELOG.md b/packages/webview_flutter/webview_flutter_wkwebview/CHANGELOG.md
index 94ea0ff9f2a..3e4efd568c4 100644
--- a/packages/webview_flutter/webview_flutter_wkwebview/CHANGELOG.md
+++ b/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
diff --git a/packages/webview_flutter/webview_flutter_wkwebview/example/integration_test/webview_flutter_test.dart b/packages/webview_flutter/webview_flutter_wkwebview/example/integration_test/webview_flutter_test.dart
index 24e70d775b1..71f6c666a36 100644
--- a/packages/webview_flutter/webview_flutter_wkwebview/example/integration_test/webview_flutter_test.dart
+++ b/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>();
diff --git a/packages/webview_flutter/webview_flutter_wkwebview/lib/src/common/weak_reference_utils.dart b/packages/webview_flutter/webview_flutter_wkwebview/lib/src/common/weak_reference_utils.dart
index f12485ad6e7..e3aead42f13 100644
--- a/packages/webview_flutter/webview_flutter_wkwebview/lib/src/common/weak_reference_utils.dart
+++ b/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() ?? '',
 ///         );
 ///       };
 ///     },
diff --git a/packages/webview_flutter/webview_flutter_wkwebview/lib/src/webkit_webview_controller.dart b/packages/webview_flutter/webview_flutter_wkwebview/lib/src/webkit_webview_controller.dart
index 4bf9d87aedf..d43f1c0c53e 100644
--- a/packages/webview_flutter/webview_flutter_wkwebview/lib/src/webkit_webview_controller.dart
+++ b/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() ?? ''),
                   );
                 }
               };
diff --git a/packages/webview_flutter/webview_flutter_wkwebview/pubspec.yaml b/packages/webview_flutter/webview_flutter_wkwebview/pubspec.yaml
index 518e0b3465c..5a0e7ed115a 100644
--- a/packages/webview_flutter/webview_flutter_wkwebview/pubspec.yaml
+++ b/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

From 153a85cc8372b5dd39c127a373fb8a69fae2c3db Mon Sep 17 00:00:00 2001
From: Maurice Parrish <10687576+bparrishMines@users.noreply.github.com>
Date: Thu, 20 Mar 2025 23:20:48 -0400
Subject: [PATCH 02/10] javascript spelling

---
 packages/webview_flutter/webview_flutter_wkwebview/CHANGELOG.md | 2 +-
 .../example/integration_test/webview_flutter_test.dart          | 2 +-
 2 files changed, 2 insertions(+), 2 deletions(-)

diff --git a/packages/webview_flutter/webview_flutter_wkwebview/CHANGELOG.md b/packages/webview_flutter/webview_flutter_wkwebview/CHANGELOG.md
index 38ab1e044ac..a4ea405f961 100644
--- a/packages/webview_flutter/webview_flutter_wkwebview/CHANGELOG.md
+++ b/packages/webview_flutter/webview_flutter_wkwebview/CHANGELOG.md
@@ -1,6 +1,6 @@
 ## 3.18.5
 
-* Fixes crash when sending undefined message via javascript channel.
+* Fixes crash when sending undefined message via JavaScript channel.
 
 ## 3.18.4
 
diff --git a/packages/webview_flutter/webview_flutter_wkwebview/example/integration_test/webview_flutter_test.dart b/packages/webview_flutter/webview_flutter_wkwebview/example/integration_test/webview_flutter_test.dart
index 71f6c666a36..5f67cfab257 100644
--- a/packages/webview_flutter/webview_flutter_wkwebview/example/integration_test/webview_flutter_test.dart
+++ b/packages/webview_flutter/webview_flutter_wkwebview/example/integration_test/webview_flutter_test.dart
@@ -278,7 +278,7 @@ Future<void> main() async {
     await expectLater(channelCompleter.future, completion('hello'));
   });
 
-  testWidgets('JavascriptChannel can receive undefined',
+  testWidgets('JavaScriptChannel can receive undefined',
       (WidgetTester tester) async {
     final Completer<void> pageFinished = Completer<void>();
     final PlatformWebViewController controller = PlatformWebViewController(

From 136205679dfe82d59d9925ba54a1daba089116c8 Mon Sep 17 00:00:00 2001
From: LinXunFeng <linxunfeng@yeah.net>
Date: Mon, 24 Mar 2025 18:25:28 +0800
Subject: [PATCH 03/10] Preserve undefined and null output

---
 .../webview_flutter_test.dart                 | 11 +++--
 .../lib/src/webkit_webview_controller.dart    | 42 +++++++++++++++++++
 .../test/webkit_webview_controller_test.dart  |  4 +-
 3 files changed, 51 insertions(+), 6 deletions(-)

diff --git a/packages/webview_flutter/webview_flutter_wkwebview/example/integration_test/webview_flutter_test.dart b/packages/webview_flutter/webview_flutter_wkwebview/example/integration_test/webview_flutter_test.dart
index 5f67cfab257..2dc3155b776 100644
--- a/packages/webview_flutter/webview_flutter_wkwebview/example/integration_test/webview_flutter_test.dart
+++ b/packages/webview_flutter/webview_flutter_wkwebview/example/integration_test/webview_flutter_test.dart
@@ -278,7 +278,7 @@ Future<void> main() async {
     await expectLater(channelCompleter.future, completion('hello'));
   });
 
-  testWidgets('JavaScriptChannel can receive undefined',
+  testWidgets('JavaScriptChannel can receive undefined and null',
       (WidgetTester tester) async {
     final Completer<void> pageFinished = Completer<void>();
     final PlatformWebViewController controller = PlatformWebViewController(
@@ -291,12 +291,12 @@ Future<void> main() async {
     unawaited(delegate.setOnPageFinished((_) => pageFinished.complete()));
     unawaited(controller.setPlatformNavigationDelegate(delegate));
 
-    final Completer<String> channelCompleter = Completer<String>();
+    final List<String> messages = <String>[];
     await controller.addJavaScriptChannel(
       JavaScriptChannelParams(
         name: 'Channel',
         onMessageReceived: (JavaScriptMessage message) {
-          channelCompleter.complete(message.message);
+          messages.add(message.message);
         },
       ),
     );
@@ -316,7 +316,10 @@ Future<void> main() async {
     await pageFinished.future;
 
     await controller.runJavaScript('Channel.postMessage(undefined);');
-    await expectLater(channelCompleter.future, completion(''));
+    await controller.runJavaScript('Channel.postMessage(null);');
+
+    await tester.pumpAndSettle();
+    expect(messages, <String>['undefined', 'null']);
   });
 
   testWidgets('resize webview', (WidgetTester tester) async {
diff --git a/packages/webview_flutter/webview_flutter_wkwebview/lib/src/webkit_webview_controller.dart b/packages/webview_flutter/webview_flutter_wkwebview/lib/src/webkit_webview_controller.dart
index aca488ea9f9..81089b9e6e7 100644
--- a/packages/webview_flutter/webview_flutter_wkwebview/lib/src/webkit_webview_controller.dart
+++ b/packages/webview_flutter/webview_flutter_wkwebview/lib/src/webkit_webview_controller.dart
@@ -443,6 +443,7 @@ class WebKitWebViewController extends PlatformWebViewController {
         webKitParams.name,
       ),
     ]);
+    await _injectPostMessageOverride(webKitParams.name);
   }
 
   @override
@@ -768,6 +769,47 @@ window.addEventListener("error", function(e) {
     await controller.addUserScript(overrideScript);
   }
 
+  Future<void> _injectPostMessageOverride(String channelName) async {
+    final WKUserScript overrideScript =
+        _webKitParams.webKitProxy.newWKUserScript(
+      source: '''
+var _flutter_webview_plugin_overrides = _flutter_webview_plugin_overrides || {};
+
+_flutter_webview_plugin_overrides.originalPostMessageFunctions = _flutter_webview_plugin_overrides.originalPostMessageFunctions || {};
+
+(function() {
+  if (window.webkit && window.webkit.messageHandlers) {
+    const handlerName = "$channelName";
+    const handler = window.webkit.messageHandlers[handlerName];
+    
+    if (handler && 
+        typeof handler.postMessage === 'function' &&
+        !_flutter_webview_plugin_overrides.originalPostMessageFunctions[handlerName]) {
+      
+      _flutter_webview_plugin_overrides.originalPostMessageFunctions[handlerName] = handler.postMessage;
+
+      handler.postMessage = function(data) {
+        if (data === undefined) {
+          return _flutter_webview_plugin_overrides.originalPostMessageFunctions[handlerName].call(this, "undefined");
+        }
+        if (data === null) {
+          return _flutter_webview_plugin_overrides.originalPostMessageFunctions[handlerName].call(this, "null");
+        }
+        return _flutter_webview_plugin_overrides.originalPostMessageFunctions[handlerName].call(this, data);
+      };
+    }
+  }
+})();
+      ''',
+      injectionTime: UserScriptInjectionTime.atDocumentStart,
+      isForMainFrameOnly: false,
+    );
+
+    final WKUserContentController controller =
+        await _webView.configuration.getUserContentController();
+    await controller.addUserScript(overrideScript);
+  }
+
   // WKWebView does not support removing a single user script, so all user
   // scripts and all message handlers are removed instead. And the JavaScript
   // channels that shouldn't be removed are re-registered. Note that this
diff --git a/packages/webview_flutter/webview_flutter_wkwebview/test/webkit_webview_controller_test.dart b/packages/webview_flutter/webview_flutter_wkwebview/test/webkit_webview_controller_test.dart
index e6a350de4e6..c8240c2ae19 100644
--- a/packages/webview_flutter/webview_flutter_wkwebview/test/webkit_webview_controller_test.dart
+++ b/packages/webview_flutter/webview_flutter_wkwebview/test/webkit_webview_controller_test.dart
@@ -863,7 +863,7 @@ void main() {
       final WKUserScript userScript =
           verify(mockUserContentController.addUserScript(captureAny))
               .captured
-              .single as WKUserScript;
+              .toList().first as WKUserScript;
       expect(userScript.source, 'window.name = webkit.messageHandlers.name;');
       expect(
         userScript.injectionTime,
@@ -1008,7 +1008,7 @@ void main() {
       final WKUserScript userScript =
           verify(mockUserContentController.addUserScript(captureAny))
               .captured
-              .single as WKUserScript;
+              .toList().first as WKUserScript;
       expect(userScript.source, 'window.name2 = webkit.messageHandlers.name2;');
       expect(
         userScript.injectionTime,

From 5c7801befbb1ace3ac1947740b5f26adba883351 Mon Sep 17 00:00:00 2001
From: LinXunFeng <linxunfeng@yeah.net>
Date: Mon, 24 Mar 2025 18:50:52 +0800
Subject: [PATCH 04/10] Code formatting

---
 .../test/webkit_webview_controller_test.dart                | 6 ++++--
 1 file changed, 4 insertions(+), 2 deletions(-)

diff --git a/packages/webview_flutter/webview_flutter_wkwebview/test/webkit_webview_controller_test.dart b/packages/webview_flutter/webview_flutter_wkwebview/test/webkit_webview_controller_test.dart
index c8240c2ae19..94998a635f5 100644
--- a/packages/webview_flutter/webview_flutter_wkwebview/test/webkit_webview_controller_test.dart
+++ b/packages/webview_flutter/webview_flutter_wkwebview/test/webkit_webview_controller_test.dart
@@ -863,7 +863,8 @@ void main() {
       final WKUserScript userScript =
           verify(mockUserContentController.addUserScript(captureAny))
               .captured
-              .toList().first as WKUserScript;
+              .toList()
+              .first as WKUserScript;
       expect(userScript.source, 'window.name = webkit.messageHandlers.name;');
       expect(
         userScript.injectionTime,
@@ -1008,7 +1009,8 @@ void main() {
       final WKUserScript userScript =
           verify(mockUserContentController.addUserScript(captureAny))
               .captured
-              .toList().first as WKUserScript;
+              .toList()
+              .first as WKUserScript;
       expect(userScript.source, 'window.name2 = webkit.messageHandlers.name2;');
       expect(
         userScript.injectionTime,

From 83b1aed2bc38e1b85b07064963885d40d8274df9 Mon Sep 17 00:00:00 2001
From: LinXunFeng <linxunfeng@yeah.net>
Date: Mon, 24 Mar 2025 19:09:33 +0800
Subject: [PATCH 05/10] update

---
 .../test/webkit_webview_controller_test.dart                    | 2 --
 1 file changed, 2 deletions(-)

diff --git a/packages/webview_flutter/webview_flutter_wkwebview/test/webkit_webview_controller_test.dart b/packages/webview_flutter/webview_flutter_wkwebview/test/webkit_webview_controller_test.dart
index 94998a635f5..edd6730946f 100644
--- a/packages/webview_flutter/webview_flutter_wkwebview/test/webkit_webview_controller_test.dart
+++ b/packages/webview_flutter/webview_flutter_wkwebview/test/webkit_webview_controller_test.dart
@@ -863,7 +863,6 @@ void main() {
       final WKUserScript userScript =
           verify(mockUserContentController.addUserScript(captureAny))
               .captured
-              .toList()
               .first as WKUserScript;
       expect(userScript.source, 'window.name = webkit.messageHandlers.name;');
       expect(
@@ -1009,7 +1008,6 @@ void main() {
       final WKUserScript userScript =
           verify(mockUserContentController.addUserScript(captureAny))
               .captured
-              .toList()
               .first as WKUserScript;
       expect(userScript.source, 'window.name2 = webkit.messageHandlers.name2;');
       expect(

From feb84e291947433016e91a178d41b374c5a99675 Mon Sep 17 00:00:00 2001
From: LinXunFeng <linxunfeng@yeah.net>
Date: Mon, 24 Mar 2025 23:49:25 +0800
Subject: [PATCH 06/10] Revert "update"

This reverts commit 83b1aed2bc38e1b85b07064963885d40d8274df9.
---
 .../test/webkit_webview_controller_test.dart                    | 2 ++
 1 file changed, 2 insertions(+)

diff --git a/packages/webview_flutter/webview_flutter_wkwebview/test/webkit_webview_controller_test.dart b/packages/webview_flutter/webview_flutter_wkwebview/test/webkit_webview_controller_test.dart
index edd6730946f..94998a635f5 100644
--- a/packages/webview_flutter/webview_flutter_wkwebview/test/webkit_webview_controller_test.dart
+++ b/packages/webview_flutter/webview_flutter_wkwebview/test/webkit_webview_controller_test.dart
@@ -863,6 +863,7 @@ void main() {
       final WKUserScript userScript =
           verify(mockUserContentController.addUserScript(captureAny))
               .captured
+              .toList()
               .first as WKUserScript;
       expect(userScript.source, 'window.name = webkit.messageHandlers.name;');
       expect(
@@ -1008,6 +1009,7 @@ void main() {
       final WKUserScript userScript =
           verify(mockUserContentController.addUserScript(captureAny))
               .captured
+              .toList()
               .first as WKUserScript;
       expect(userScript.source, 'window.name2 = webkit.messageHandlers.name2;');
       expect(

From 77bec509c5ecb884ed4dcdc1ffa449ace3cff7b5 Mon Sep 17 00:00:00 2001
From: LinXunFeng <linxunfeng@yeah.net>
Date: Mon, 24 Mar 2025 23:49:31 +0800
Subject: [PATCH 07/10] Revert "Code formatting"

This reverts commit 5c7801befbb1ace3ac1947740b5f26adba883351.
---
 .../test/webkit_webview_controller_test.dart                | 6 ++----
 1 file changed, 2 insertions(+), 4 deletions(-)

diff --git a/packages/webview_flutter/webview_flutter_wkwebview/test/webkit_webview_controller_test.dart b/packages/webview_flutter/webview_flutter_wkwebview/test/webkit_webview_controller_test.dart
index 94998a635f5..c8240c2ae19 100644
--- a/packages/webview_flutter/webview_flutter_wkwebview/test/webkit_webview_controller_test.dart
+++ b/packages/webview_flutter/webview_flutter_wkwebview/test/webkit_webview_controller_test.dart
@@ -863,8 +863,7 @@ void main() {
       final WKUserScript userScript =
           verify(mockUserContentController.addUserScript(captureAny))
               .captured
-              .toList()
-              .first as WKUserScript;
+              .toList().first as WKUserScript;
       expect(userScript.source, 'window.name = webkit.messageHandlers.name;');
       expect(
         userScript.injectionTime,
@@ -1009,8 +1008,7 @@ void main() {
       final WKUserScript userScript =
           verify(mockUserContentController.addUserScript(captureAny))
               .captured
-              .toList()
-              .first as WKUserScript;
+              .toList().first as WKUserScript;
       expect(userScript.source, 'window.name2 = webkit.messageHandlers.name2;');
       expect(
         userScript.injectionTime,

From db6b43a807fa9b405d741caf30031b5ee3bb464e Mon Sep 17 00:00:00 2001
From: LinXunFeng <linxunfeng@yeah.net>
Date: Mon, 24 Mar 2025 23:49:42 +0800
Subject: [PATCH 08/10] Revert "Preserve undefined and null output"

This reverts commit 136205679dfe82d59d9925ba54a1daba089116c8.
---
 .../webview_flutter_test.dart                 | 11 ++---
 .../lib/src/webkit_webview_controller.dart    | 42 -------------------
 .../test/webkit_webview_controller_test.dart  |  4 +-
 3 files changed, 6 insertions(+), 51 deletions(-)

diff --git a/packages/webview_flutter/webview_flutter_wkwebview/example/integration_test/webview_flutter_test.dart b/packages/webview_flutter/webview_flutter_wkwebview/example/integration_test/webview_flutter_test.dart
index 2dc3155b776..5f67cfab257 100644
--- a/packages/webview_flutter/webview_flutter_wkwebview/example/integration_test/webview_flutter_test.dart
+++ b/packages/webview_flutter/webview_flutter_wkwebview/example/integration_test/webview_flutter_test.dart
@@ -278,7 +278,7 @@ Future<void> main() async {
     await expectLater(channelCompleter.future, completion('hello'));
   });
 
-  testWidgets('JavaScriptChannel can receive undefined and null',
+  testWidgets('JavaScriptChannel can receive undefined',
       (WidgetTester tester) async {
     final Completer<void> pageFinished = Completer<void>();
     final PlatformWebViewController controller = PlatformWebViewController(
@@ -291,12 +291,12 @@ Future<void> main() async {
     unawaited(delegate.setOnPageFinished((_) => pageFinished.complete()));
     unawaited(controller.setPlatformNavigationDelegate(delegate));
 
-    final List<String> messages = <String>[];
+    final Completer<String> channelCompleter = Completer<String>();
     await controller.addJavaScriptChannel(
       JavaScriptChannelParams(
         name: 'Channel',
         onMessageReceived: (JavaScriptMessage message) {
-          messages.add(message.message);
+          channelCompleter.complete(message.message);
         },
       ),
     );
@@ -316,10 +316,7 @@ Future<void> main() async {
     await pageFinished.future;
 
     await controller.runJavaScript('Channel.postMessage(undefined);');
-    await controller.runJavaScript('Channel.postMessage(null);');
-
-    await tester.pumpAndSettle();
-    expect(messages, <String>['undefined', 'null']);
+    await expectLater(channelCompleter.future, completion(''));
   });
 
   testWidgets('resize webview', (WidgetTester tester) async {
diff --git a/packages/webview_flutter/webview_flutter_wkwebview/lib/src/webkit_webview_controller.dart b/packages/webview_flutter/webview_flutter_wkwebview/lib/src/webkit_webview_controller.dart
index 81089b9e6e7..aca488ea9f9 100644
--- a/packages/webview_flutter/webview_flutter_wkwebview/lib/src/webkit_webview_controller.dart
+++ b/packages/webview_flutter/webview_flutter_wkwebview/lib/src/webkit_webview_controller.dart
@@ -443,7 +443,6 @@ class WebKitWebViewController extends PlatformWebViewController {
         webKitParams.name,
       ),
     ]);
-    await _injectPostMessageOverride(webKitParams.name);
   }
 
   @override
@@ -769,47 +768,6 @@ window.addEventListener("error", function(e) {
     await controller.addUserScript(overrideScript);
   }
 
-  Future<void> _injectPostMessageOverride(String channelName) async {
-    final WKUserScript overrideScript =
-        _webKitParams.webKitProxy.newWKUserScript(
-      source: '''
-var _flutter_webview_plugin_overrides = _flutter_webview_plugin_overrides || {};
-
-_flutter_webview_plugin_overrides.originalPostMessageFunctions = _flutter_webview_plugin_overrides.originalPostMessageFunctions || {};
-
-(function() {
-  if (window.webkit && window.webkit.messageHandlers) {
-    const handlerName = "$channelName";
-    const handler = window.webkit.messageHandlers[handlerName];
-    
-    if (handler && 
-        typeof handler.postMessage === 'function' &&
-        !_flutter_webview_plugin_overrides.originalPostMessageFunctions[handlerName]) {
-      
-      _flutter_webview_plugin_overrides.originalPostMessageFunctions[handlerName] = handler.postMessage;
-
-      handler.postMessage = function(data) {
-        if (data === undefined) {
-          return _flutter_webview_plugin_overrides.originalPostMessageFunctions[handlerName].call(this, "undefined");
-        }
-        if (data === null) {
-          return _flutter_webview_plugin_overrides.originalPostMessageFunctions[handlerName].call(this, "null");
-        }
-        return _flutter_webview_plugin_overrides.originalPostMessageFunctions[handlerName].call(this, data);
-      };
-    }
-  }
-})();
-      ''',
-      injectionTime: UserScriptInjectionTime.atDocumentStart,
-      isForMainFrameOnly: false,
-    );
-
-    final WKUserContentController controller =
-        await _webView.configuration.getUserContentController();
-    await controller.addUserScript(overrideScript);
-  }
-
   // WKWebView does not support removing a single user script, so all user
   // scripts and all message handlers are removed instead. And the JavaScript
   // channels that shouldn't be removed are re-registered. Note that this
diff --git a/packages/webview_flutter/webview_flutter_wkwebview/test/webkit_webview_controller_test.dart b/packages/webview_flutter/webview_flutter_wkwebview/test/webkit_webview_controller_test.dart
index c8240c2ae19..e6a350de4e6 100644
--- a/packages/webview_flutter/webview_flutter_wkwebview/test/webkit_webview_controller_test.dart
+++ b/packages/webview_flutter/webview_flutter_wkwebview/test/webkit_webview_controller_test.dart
@@ -863,7 +863,7 @@ void main() {
       final WKUserScript userScript =
           verify(mockUserContentController.addUserScript(captureAny))
               .captured
-              .toList().first as WKUserScript;
+              .single as WKUserScript;
       expect(userScript.source, 'window.name = webkit.messageHandlers.name;');
       expect(
         userScript.injectionTime,
@@ -1008,7 +1008,7 @@ void main() {
       final WKUserScript userScript =
           verify(mockUserContentController.addUserScript(captureAny))
               .captured
-              .toList().first as WKUserScript;
+              .single as WKUserScript;
       expect(userScript.source, 'window.name2 = webkit.messageHandlers.name2;');
       expect(
         userScript.injectionTime,

From ef6ccae30679874f210812532d5ac4d61a7bb556 Mon Sep 17 00:00:00 2001
From: LinXunFeng <linxunfeng@yeah.net>
Date: Tue, 25 Mar 2025 09:41:40 +0800
Subject: [PATCH 09/10] Return '(null)' when message.body is null

---
 .../example/integration_test/webview_flutter_test.dart     | 2 +-
 .../lib/src/webkit_webview_controller.dart                 | 7 ++++++-
 2 files changed, 7 insertions(+), 2 deletions(-)

diff --git a/packages/webview_flutter/webview_flutter_wkwebview/example/integration_test/webview_flutter_test.dart b/packages/webview_flutter/webview_flutter_wkwebview/example/integration_test/webview_flutter_test.dart
index 5f67cfab257..83a13e3d6bb 100644
--- a/packages/webview_flutter/webview_flutter_wkwebview/example/integration_test/webview_flutter_test.dart
+++ b/packages/webview_flutter/webview_flutter_wkwebview/example/integration_test/webview_flutter_test.dart
@@ -316,7 +316,7 @@ Future<void> main() async {
     await pageFinished.future;
 
     await controller.runJavaScript('Channel.postMessage(undefined);');
-    await expectLater(channelCompleter.future, completion(''));
+    await expectLater(channelCompleter.future, completion('(null)'));
   });
 
   testWidgets('resize webview', (WidgetTester tester) async {
diff --git a/packages/webview_flutter/webview_flutter_wkwebview/lib/src/webkit_webview_controller.dart b/packages/webview_flutter/webview_flutter_wkwebview/lib/src/webkit_webview_controller.dart
index aca488ea9f9..42b6a4cac97 100644
--- a/packages/webview_flutter/webview_flutter_wkwebview/lib/src/webkit_webview_controller.dart
+++ b/packages/webview_flutter/webview_flutter_wkwebview/lib/src/webkit_webview_controller.dart
@@ -905,8 +905,13 @@ class WebKitJavaScriptChannelParams extends JavaScriptChannelParams {
             (WeakReference<void Function(JavaScriptMessage)> weakReference) {
               return (_, __, WKScriptMessage message) {
                 if (weakReference.target != null) {
+                  // When message.body is null, return '(null)' for consistency
+                  // with previous implementations.
                   weakReference.target!(
-                    JavaScriptMessage(message: message.body?.toString() ?? ''),
+                    JavaScriptMessage(
+                        message: message.body == null
+                            ? '(null)'
+                            : message.body!.toString()),
                   );
                 }
               };

From 4bde9bceb2f47a444023a3f4c79c084eabd06f5c Mon Sep 17 00:00:00 2001
From: LinXunFeng <linxunfeng@yeah.net>
Date: Wed, 26 Mar 2025 09:57:43 +0800
Subject: [PATCH 10/10] Remove unnecessary symbols

---
 .../lib/src/common/weak_reference_utils.dart                    | 2 +-
 .../lib/src/legacy/web_kit_webview_widget.dart                  | 2 +-
 .../lib/src/webkit_webview_controller.dart                      | 2 +-
 3 files changed, 3 insertions(+), 3 deletions(-)

diff --git a/packages/webview_flutter/webview_flutter_wkwebview/lib/src/common/weak_reference_utils.dart b/packages/webview_flutter/webview_flutter_wkwebview/lib/src/common/weak_reference_utils.dart
index e3aead42f13..014d9eb42ea 100644
--- a/packages/webview_flutter/webview_flutter_wkwebview/lib/src/common/weak_reference_utils.dart
+++ b/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(),
 ///         );
 ///       };
 ///     },
diff --git a/packages/webview_flutter/webview_flutter_wkwebview/lib/src/legacy/web_kit_webview_widget.dart b/packages/webview_flutter/webview_flutter_wkwebview/lib/src/legacy/web_kit_webview_widget.dart
index 016f1734b94..89e184a89a5 100644
--- a/packages/webview_flutter/webview_flutter_wkwebview/lib/src/legacy/web_kit_webview_widget.dart
+++ b/packages/webview_flutter/webview_flutter_wkwebview/lib/src/legacy/web_kit_webview_widget.dart
@@ -456,7 +456,7 @@ class WebKitWebViewPlatformController extends WebViewPlatformController {
                 ) {
                   weakReference.target?.onJavascriptChannelMessage(
                     message.name,
-                    message.body!.toString(),
+                    message.body.toString(),
                   );
                 };
               },
diff --git a/packages/webview_flutter/webview_flutter_wkwebview/lib/src/webkit_webview_controller.dart b/packages/webview_flutter/webview_flutter_wkwebview/lib/src/webkit_webview_controller.dart
index 42b6a4cac97..843c73f3de3 100644
--- a/packages/webview_flutter/webview_flutter_wkwebview/lib/src/webkit_webview_controller.dart
+++ b/packages/webview_flutter/webview_flutter_wkwebview/lib/src/webkit_webview_controller.dart
@@ -911,7 +911,7 @@ class WebKitJavaScriptChannelParams extends JavaScriptChannelParams {
                     JavaScriptMessage(
                         message: message.body == null
                             ? '(null)'
-                            : message.body!.toString()),
+                            : message.body.toString()),
                   );
                 }
               };