[camera] Fix web facingMode capability handling

packages/camera/camera_web/CHANGELOG.md

@@ -1,11 +1,13 @@
-## NEXT
+## 0.3.5+4
 
+* Fixes a `TypeError` in `availableCameras()` caused by browsers (e.g. Firefox) returning
+  an invalid `facingMode` capability value instead of the expected `DOMString` sequence.
 * Updates minimum supported SDK version to Flutter 3.38/Dart 3.10.
 
 ## 0.3.5+3
 
 * Fixes camera initialization failure on Safari by fixing a null check operator error using
-  a nullable getter and null safe practices.
+  a nullable getter and null-safe practices.
 
 ## 0.3.5+2
 

packages/camera/camera_web/example/integration_test/camera_service_test.dart

@@ -512,6 +512,46 @@ void main() {
           expect(facingMode, equals('environment'));
         });
 
+        testWidgets('returns null '
+            'when the facing mode setting is empty and '
+            'the first facingMode capability is not a JavaScript string', (
+          WidgetTester tester,
+        ) async {
+          mockVideoTrack.getSettings = () {
+            return web.MediaTrackSettings(facingMode: '');
+          }.toJS;
+          mockVideoTrack.getCapabilities = () {
+            return createJSInteropWrapper(FakeMediaTrackCapabilities())
+                as web.MediaTrackCapabilities;
+          }.toJS;
+
+          when(jsUtil.hasProperty(videoTrack, 'getCapabilities'.toJS)).thenReturn(true);
+          when(jsUtil.getProperty(any, 'facingMode'.toJS)).thenReturn(<JSAny>[true.toJS].toJS);
+
+          final String? facingMode = cameraService.getFacingModeForVideoTrack(videoTrack);
+
+          expect(facingMode, isNull);
+        });
+
+        testWidgets('returns null '
+            'when the facing mode setting is empty and '
+            'the facingMode capability is not a JavaScript array', (WidgetTester tester) async {
+          mockVideoTrack.getSettings = () {
+            return web.MediaTrackSettings(facingMode: '');
+          }.toJS;
+          mockVideoTrack.getCapabilities = () {
+            return createJSInteropWrapper(FakeMediaTrackCapabilities())
+                as web.MediaTrackCapabilities;
+          }.toJS;
+
+          when(jsUtil.hasProperty(videoTrack, 'getCapabilities'.toJS)).thenReturn(true);
+          when(jsUtil.getProperty(any, 'facingMode'.toJS)).thenReturn(true.toJS);
+
+          final String? facingMode = cameraService.getFacingModeForVideoTrack(videoTrack);
+
+          expect(facingMode, isNull);
+        });
+
         testWidgets('returns null '
             'when the facing mode setting '
             'and capabilities are empty', (WidgetTester tester) async {

packages/camera/camera_web/lib/src/camera_service.dart

@@ -196,20 +196,29 @@ class CameraService {
       final web.MediaTrackCapabilities videoTrackCapabilities = videoTrack.getCapabilities();
 
       // A list of facing mode capabilities as
-      // the camera may support multiple facing modes.
-      final List<String> facingModeCapabilities =
-          videoTrackCapabilities.facingModeNullable?.toDart
-              .map((JSString e) => e.toDart)
-              .toList() ??
-          <String>[];
-
-      if (facingModeCapabilities.isNotEmpty) {
-        final String facingModeCapability = facingModeCapabilities.first;
-        return facingModeCapability;
-      } else {
-        // Return null if there are no facing mode capabilities.
+      //The camera may support multiple facing modes.
+      // Some browsers (e.g., Firefox) do not conform to the MediaTrackCapabilities
+      // spec and may return `facingMode` as a non-array value (e.g., an empty string,
+      // a plain object, or a boolean) Rather than the expected DOMString sequence.
+      // We use jsUtil.getProperty to safely read the raw JS value, then explicitly
+      // validate it is a JSArray before accessing its elements to prevent a TypeError.
+
+      final JSAny? facingModeCapabilities = jsUtil.getProperty(
+        videoTrackCapabilities,
+        'facingMode'.toJS,
+      );
+      if (facingModeCapabilities == null || !facingModeCapabilities.isA<JSArray>()) {
         return null;
       }
+
+      final List<JSAny?> facingModes = (facingModeCapabilities as JSArray).toDart;
+
+      if (facingModes.isNotEmpty && facingModes.first.isA<JSString>()) {
+        return (facingModes.first! as JSString).toDart;
+      }
+
+      // Return null if there are no facing mode capabilities.
+      return null;
     }
 
     return facingMode;

packages/camera/camera_web/pubspec.yaml

@@ -2,7 +2,7 @@ name: camera_web
 description: A Flutter plugin for getting information about and controlling the camera on Web.
 repository: https://github.com/flutter/packages/tree/main/packages/camera/camera_web
 issue_tracker: https://github.com/flutter/flutter/issues?q=is%3Aissue+is%3Aopen+label%3A%22p%3A+camera%22
-version: 0.3.5+3
+version: 0.3.5+4
 
 environment:
   sdk: ^3.10.0