Send empty composing range to engine if invalid

packages/fleather/lib/src/widgets/editor_input_client_mixin.dart

@@ -95,7 +95,7 @@ mixin RawEditorStateTextInputClientMixin on EditorState
     // with the last known remote value.
     // It is important to prevent excessive remote updates as it can cause
     // race conditions.
-    final actualValue = value.copyWith(
+    var actualValue = value.copyWith(
       composing: _lastKnownRemoteTextEditingValue?.composing,
     );
 
@@ -107,6 +107,17 @@ mixin RawEditorStateTextInputClientMixin on EditorState
       performSpellCheck(value.text);
     }
 
+    // This is to prevent sending an editing state with invalid composing range
+    // to engine.
+    // TODO: Maybe it's better to also include composing range in controller?
+    // Actions like [_DeleteTextAction] are using controller's editing value
+    // to update remote value.
+    // See https://github.com/fleather-editor/fleather/issues/259#issuecomment-2032404450
+    if (actualValue.composing != TextRange.empty &&
+        !actualValue.isComposingRangeValid) {
+      actualValue = actualValue.copyWith(composing: TextRange.empty);
+    }
+
     _lastKnownRemoteTextEditingValue = actualValue;
     _textInputConnection!.setEditingState(actualValue);
   }

packages/fleather/test/widgets/editor_input_client_mixin_test.dart

@@ -7,6 +7,55 @@ import 'package:flutter_test/flutter_test.dart';
 import '../testing.dart';
 
 void main() {
+  group('send text editing state to TextInputConnection', () {
+    final composingRanges = <TextRange>[];
+
+    void bind(WidgetTester tester) {
+      tester.binding.defaultBinaryMessenger.setMockMethodCallHandler(
+          SystemChannels.textInput, (MethodCall methodCall) async {
+        if (methodCall.method == 'TextInput.setEditingState') {
+          final Map<String, dynamic> args =
+              methodCall.arguments as Map<String, dynamic>;
+          composingRanges.add(TextRange(
+              start: args['composingBase'], end: args['composingExtent']));
+        }
+        return null;
+      });
+    }
+
+    setUp(() => composingRanges.clear());
+
+    testWidgets(
+        'sends empty composing range if composing range becomes invalid',
+        (tester) async {
+      bind(tester);
+      final document = ParchmentDocument.fromJson([
+        {'insert': 'some text\n'}
+      ]);
+      final editor = EditorSandBox(tester: tester, document: document);
+      await editor.pump();
+      await editor.tap();
+      tester.binding.scheduleWarmUpFrame();
+      final editorState =
+          tester.state(find.byType(RawEditor)) as RawEditorState;
+      editorState.updateEditingValueWithDeltas([
+        TextEditingDeltaNonTextUpdate(
+          oldText: editorState.textEditingValue.text,
+          selection: const TextSelection.collapsed(offset: 9),
+          composing: const TextRange(start: 5, end: 9),
+        )
+      ]);
+      await tester.pumpAndSettle();
+      editor.controller.replaceText(4, 5, '',
+          selection: const TextSelection.collapsed(offset: 4));
+      await tester.pumpAndSettle(throttleDuration);
+      expect(
+          composingRanges.fold(
+              true, (v, e) => v && (e == TextRange.empty || e.isValid)),
+          isTrue);
+    });
+  });
+
   group('sets style to TextInputConnection', () {
     final log = <TextInputConnectionStyle>[];