Fix EditableText misplaces caret when selection is invalid (#123777)

Fix EditableText misplaces caret when selection is invalid

Author: bleroux

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

@@ -3706,6 +3706,15 @@ class EditableTextState extends State<EditableText> with AutomaticKeepAliveClien
   }
 
   void _didChangeTextEditingValue() {
+    if (_hasFocus && !_value.selection.isValid) {
+      // If this field is focused and the selection is invalid, place the cursor at
+      // the end. Does not rely on _handleFocusChanged because it makes selection
+      // handles visible on Android.
+      // Unregister as a listener to the text controller while making the change.
+      widget.controller.removeListener(_didChangeTextEditingValue);
+      widget.controller.selection = _adjustedSelectionWhenFocused()!;
+      widget.controller.addListener(_didChangeTextEditingValue);
+    }
     _updateRemoteEditingValueIfNeeded();
     _startOrStopCursorTimerIfNeeded();
     _updateOrDisposeSelectionOverlayIfNeeded();
@@ -3726,21 +3735,9 @@ class EditableTextState extends State<EditableText> with AutomaticKeepAliveClien
       if (!widget.readOnly) {
         _scheduleShowCaretOnScreen(withAnimation: true);
       }
-      final bool shouldSelectAll = widget.selectionEnabled && kIsWeb
-          && !_isMultiline && !_nextFocusChangeIsInternal;
-      if (shouldSelectAll) {
-        // On native web, single line <input> tags select all when receiving
-        // focus.
-        _handleSelectionChanged(
-          TextSelection(
-            baseOffset: 0,
-            extentOffset: _value.text.length,
-          ),
-          null,
-        );
-      } else if (!_value.selection.isValid) {
-        // Place cursor at the end if the selection is invalid when we receive focus.
-        _handleSelectionChanged(TextSelection.collapsed(offset: _value.text.length), null);
+      final TextSelection? updatedSelection = _adjustedSelectionWhenFocused();
+      if (updatedSelection != null) {
+        _handleSelectionChanged(updatedSelection, null);
       }
     } else {
       WidgetsBinding.instance.removeObserver(this);
@@ -3749,6 +3746,24 @@ class EditableTextState extends State<EditableText> with AutomaticKeepAliveClien
     updateKeepAlive();
   }
 
+  TextSelection? _adjustedSelectionWhenFocused() {
+    TextSelection? selection;
+    final bool shouldSelectAll = widget.selectionEnabled && kIsWeb
+        && !_isMultiline && !_nextFocusChangeIsInternal;
+    if (shouldSelectAll) {
+      // On native web, single line <input> tags select all when receiving
+      // focus.
+      selection = TextSelection(
+        baseOffset: 0,
+        extentOffset: _value.text.length,
+      );
+    } else if (!_value.selection.isValid) {
+      // Place cursor at the end if the selection is invalid when we receive focus.
+      selection = TextSelection.collapsed(offset: _value.text.length);
+    }
+    return selection;
+  }
+
   void _compositeCallback(Layer layer) {
     // The callback can be invoked when the layer is detached.
     // The input connection can be closed by the platform in which case this

packages/flutter/test/material/text_field_test.dart

@@ -6744,8 +6744,8 @@ void main() {
     variant: KeySimulatorTransitModeVariant.all()
   );
 
-  // Regressing test for https://github.com/flutter/flutter/issues/78219
-  testWidgets('Paste does not crash when the section is inValid', (WidgetTester tester) async {
+  // Regression test for https://github.com/flutter/flutter/issues/78219
+  testWidgets('Paste does not crash after calling TextController.text setter', (WidgetTester tester) async {
     final FocusNode focusNode = FocusNode();
     final TextEditingController controller = TextEditingController();
     final TextField textField = TextField(
@@ -6778,7 +6778,7 @@ void main() {
     await tester.tap(find.byType(TextField));
     await tester.pumpAndSettle();
 
-    // This setter will set `selection` invalid.
+    // Clear the text.
     controller.text = '';
 
     // Paste clipboardContent to the text field.
@@ -6790,10 +6790,12 @@ void main() {
     await tester.sendKeyUpEvent(LogicalKeyboardKey.controlRight);
     await tester.pumpAndSettle();
 
-    // Do nothing.
-    expect(find.text(clipboardContent), findsNothing);
-    expect(controller.selection, const TextSelection.collapsed(offset: -1));
-  }, variant: KeySimulatorTransitModeVariant.all());
+    // Clipboard content is correctly pasted.
+    expect(find.text(clipboardContent), findsOneWidget);
+  },
+    skip: areKeyEventsHandledByPlatform, // [intended] only applies to platforms where we handle key events.
+    variant: KeySimulatorTransitModeVariant.all(),
+  );
 
   testWidgets('Cut test', (WidgetTester tester) async {
     final FocusNode focusNode = FocusNode();

packages/flutter/test/widgets/editable_text_shortcuts_test.dart

@@ -90,38 +90,6 @@ void main() {
     );
   }
 
-  testWidgets(
-    'Movement/Deletion shortcuts do nothing when the selection is invalid',
-    (WidgetTester tester) async {
-      await tester.pumpWidget(buildEditableText());
-      controller.text = testText;
-      controller.selection = const TextSelection.collapsed(offset: -1);
-      await tester.pump();
-
-      const List<LogicalKeyboardKey> triggers = <LogicalKeyboardKey>[
-        LogicalKeyboardKey.backspace,
-        LogicalKeyboardKey.delete,
-        LogicalKeyboardKey.arrowLeft,
-        LogicalKeyboardKey.arrowRight,
-        LogicalKeyboardKey.arrowUp,
-        LogicalKeyboardKey.arrowDown,
-        LogicalKeyboardKey.pageUp,
-        LogicalKeyboardKey.pageDown,
-        LogicalKeyboardKey.home,
-        LogicalKeyboardKey.end,
-      ];
-
-      for (final SingleActivator activator in triggers.expand(allModifierVariants)) {
-        await sendKeyCombination(tester, activator);
-        await tester.pump();
-        expect(controller.text, testText, reason: activator.toString());
-        expect(controller.selection, const TextSelection.collapsed(offset: -1), reason: activator.toString());
-      }
-    },
-    skip: kIsWeb, // [intended] on web these keys are handled by the browser.
-    variant: TargetPlatformVariant.all(),
-  );
-
   group('Common text editing shortcuts: ',
     () {
       final TargetPlatformVariant allExceptApple = TargetPlatformVariant.all(excluding: <TargetPlatform>{TargetPlatform.macOS, TargetPlatform.iOS});