Allow spell check to fail silently on unsupported platforms & spell checkers (#122715)

Allow spell check to fail silently on unsupported platforms & spell checkers

packages/flutter/lib/src/widgets/editable_text.dart

@@ -2409,21 +2409,35 @@ class EditableTextState extends State<EditableText> with AutomaticKeepAliveClien
   /// If spell check is enabled, this will try to infer a value for
   /// the [SpellCheckService] if left unspecified.
   static SpellCheckConfiguration _inferSpellCheckConfiguration(SpellCheckConfiguration? configuration) {
-    if (configuration == null || configuration == const SpellCheckConfiguration.disabled()) {
+    final SpellCheckService? spellCheckService = configuration?.spellCheckService;
+    final bool spellCheckAutomaticallyDisabled = configuration == null || configuration == const SpellCheckConfiguration.disabled();
+    final bool spellCheckServiceIsConfigured = spellCheckService != null || spellCheckService == null && WidgetsBinding.instance.platformDispatcher.nativeSpellCheckServiceDefined;
+    if (spellCheckAutomaticallyDisabled || !spellCheckServiceIsConfigured) {
+      // Only enable spell check if a non-disabled configuration is provided
+      // and if that configuration does not specify a spell check service,
+      // a native spell checker must be supported.
+      assert(() {
+        if (!spellCheckAutomaticallyDisabled && !spellCheckServiceIsConfigured) {
+          FlutterError.reportError(
+            FlutterErrorDetails(
+              exception: FlutterError(
+                'Spell check was enabled with spellCheckConfiguration, but the '
+                'current platform does not have a supported spell check '
+                'service, and none was provided. Consider disabling spell '
+                'check for this platform or passing a SpellCheckConfiguration '
+                'with a specified spell check service.',
+              ),
+              library: 'widget library',
+              stack: StackTrace.current,
+            ),
+          );
+        }
+        return true;
+      }());
       return const SpellCheckConfiguration.disabled();
     }
 
-    SpellCheckService? spellCheckService = configuration.spellCheckService;
-
-    assert(
-      spellCheckService != null
-      || WidgetsBinding.instance.platformDispatcher.nativeSpellCheckServiceDefined,
-      'spellCheckService must be specified for this platform because no default service available',
-    );
-
-    spellCheckService = spellCheckService ?? DefaultSpellCheckService();
-
-    return configuration.copyWith(spellCheckService: spellCheckService);
+    return configuration.copyWith(spellCheckService: spellCheckService ?? DefaultSpellCheckService());
   }
 
   /// Returns the [ContextMenuButtonItem]s for the given [ToolbarOptions].

packages/flutter/test/widgets/editable_text_test.dart

@@ -14838,28 +14838,34 @@ testWidgets('Floating cursor ending with selection', (WidgetTester tester) async
     });
 
     testWidgets(
-      'Error thrown when spell check enabled but no default spell check service available',
+      'Spell check disabled when spell check configuration specified but no default spell check service available',
         (WidgetTester tester) async {
       tester.binding.platformDispatcher.nativeSpellCheckServiceDefinedTestValue =
         false;
 
       await tester.pumpWidget(
-          EditableText(
-              controller: TextEditingController(text: 'A'),
-              focusNode: FocusNode(),
-              style: const TextStyle(),
-              cursorColor: Colors.blue,
-              backgroundCursorColor: Colors.grey,
-              cursorOpacityAnimates: true,
-              autofillHints: null,
-              spellCheckConfiguration:
-                const SpellCheckConfiguration(
-                  misspelledTextStyle: TextField.materialMisspelledTextStyle,
-              ),
-          ));
+        MaterialApp(
+          home: EditableText(
+            controller: TextEditingController(text: 'A'),
+            focusNode: FocusNode(),
+            style: const TextStyle(),
+            cursorColor: Colors.blue,
+            backgroundCursorColor: Colors.grey,
+            cursorOpacityAnimates: true,
+            autofillHints: null,
+            spellCheckConfiguration:
+              const SpellCheckConfiguration(
+                misspelledTextStyle: TextField.materialMisspelledTextStyle,
+            ),
+          ),
+        )
+      );
 
-        expect(tester.takeException(), isA<AssertionError>());
-        tester.binding.platformDispatcher.clearNativeSpellCheckServiceDefined();
+      expect(tester.takeException(), isA<AssertionError>());
+      final EditableTextState state =
+        tester.state<EditableTextState>(find.byType(EditableText));
+      expect(state.spellCheckConfiguration, equals(const SpellCheckConfiguration.disabled()));
+      tester.binding.platformDispatcher.clearNativeSpellCheckServiceDefined();
     });
 
     testWidgets(