Validate text selection before updating it inside of EditableText (#51410)

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

@@ -189,7 +189,7 @@ class TextEditingController extends ValueNotifier<TextEditingValue> {
   /// in a separate statement. To change both the [text] and the [selection]
   /// change the controller's [value].
   set selection(TextSelection newSelection) {
-    if (newSelection.start > text.length || newSelection.end > text.length)
+    if (!isSelectionWithinTextBounds(newSelection))
       throw FlutterError('invalid text selection: $newSelection');
     value = value.copyWith(selection: newSelection, composing: TextRange.empty);
   }
@@ -220,6 +220,11 @@ class TextEditingController extends ValueNotifier<TextEditingValue> {
   void clearComposing() {
     value = value.copyWith(composing: TextRange.empty);
   }
+
+  /// Check that the [selection] is inside of the bounds of [text].
+  bool isSelectionWithinTextBounds(TextSelection selection) {
+    return selection.start <= text.length && selection.end <= text.length;
+  }
 }
 
 /// Toolbar configuration for [EditableText].
@@ -1530,6 +1535,12 @@ class EditableTextState extends State<EditableText> with AutomaticKeepAliveClien
   }
 
   void _handleSelectionChanged(TextSelection selection, RenderEditable renderObject, SelectionChangedCause cause) {
+    // We return early if the selection is not valid. This can happen when the
+    // text of [EditableText] is updated at the same time as the selection is
+    // changed by a gesture event.
+    if (!widget.controller.isSelectionWithinTextBounds(selection))
+      return;
+
     widget.controller.selection = selection;
 
     // This will show the keyboard for all selection changes on the

packages/flutter/test/material/text_field_test.dart

@@ -3378,6 +3378,30 @@ void main() {
     }
   });
 
+  // Regression test for https://github.com/flutter/flutter/issues/35848
+  testWidgets('Clearing text field with suffixIcon does not cause text selection exception', (WidgetTester tester) async {
+    final TextEditingController controller = TextEditingController(
+      text: 'Prefilled text.',
+    );
+
+    await tester.pumpWidget(
+      boilerplate(
+        child: TextField(
+          controller: controller,
+          decoration: InputDecoration(
+            suffixIcon: IconButton(
+              icon: const Icon(Icons.close),
+              onPressed: controller.clear,
+            ),
+          ),
+        ),
+      ),
+    );
+
+    await tester.tap(find.byType(IconButton));
+    expect(controller.text, '');
+  });
+
   testWidgets('maxLength limits input.', (WidgetTester tester) async {
     final TextEditingController textController = TextEditingController();