Fix rendereditable to check the latest text before setting the selection (#78919)

* Fix rendereditable to check the latest text before setting the selection

* add regression comment

* addressing comments and fix tests

packages/flutter/lib/src/rendering/editable.dart

@@ -564,6 +564,21 @@ class RenderEditable extends RenderBox with RelayoutWhenSystemFontsChangeMixin {
   }
 
   void _setSelection(TextSelection nextSelection, SelectionChangedCause cause) {
+    if (nextSelection.isValid) {
+      // The nextSelection is calculated based on _plainText, which can be out
+      // of sync with the textSelectionDelegate.textEditingValue by one frame.
+      // This is due to the render editable and editable text handle pointer
+      // event separately. If the editable text changes the text during the
+      // event handler, the render editable will use the outdated text stored in
+      // the _plainText when handling the pointer event.
+      //
+      // If this happens, we need to make sure the new selection is still valid.
+      final int textLength = textSelectionDelegate.textEditingValue.text.length;
+      nextSelection = nextSelection.copyWith(
+        baseOffset: math.min(nextSelection.baseOffset, textLength),
+        extentOffset: math.min(nextSelection.extentOffset, textLength),
+      );
+    }
     _handleSelectionChange(nextSelection, cause);
     _setTextEditingValue(
       textSelectionDelegate.textEditingValue.copyWith(selection: nextSelection),

packages/flutter/test/material/text_field_test.dart

@@ -444,6 +444,33 @@ void main() {
     expect(renderEditable.cursorColor!.alpha, 0);
   }, variant: const TargetPlatformVariant(<TargetPlatform>{ TargetPlatform.iOS,  TargetPlatform.macOS }));
 
+  // Regression test for https://github.com/flutter/flutter/issues/78918.
+  testWidgets('RenderEditable sets correct text editing value', (WidgetTester tester) async {
+    final TextEditingController controller = TextEditingController(text: 'how are you');
+    final UniqueKey icon = UniqueKey();
+    await tester.pumpWidget(
+      MaterialApp(
+        home: Material(
+          child: TextField(
+            controller: controller,
+            decoration: InputDecoration(
+              suffixIcon: IconButton(
+                key: icon,
+                icon: const Icon(Icons.cancel),
+                onPressed: () => controller.clear(),
+              ),
+            ),
+          ),
+        ),
+      ),
+    );
+
+    await tester.tap(find.byKey(icon));
+    await tester.pump();
+    expect(controller.text, '');
+    expect(controller.selection, const TextSelection.collapsed(offset: 0, affinity: TextAffinity.upstream));
+  });
+
   testWidgets('Cursor radius is 2.0', (WidgetTester tester) async {
     await tester.pumpWidget(
       const MaterialApp(

packages/flutter/test/rendering/editable_test.dart

@@ -413,7 +413,9 @@ void main() {
   });
 
   test('selects correct place with offsets', () {
-    final TextSelectionDelegate delegate = FakeEditableTextState();
+    const String text = 'test\ntest';
+    final TextSelectionDelegate delegate = FakeEditableTextState()
+      ..textEditingValue = const TextEditingValue(text: text);
     final ViewportOffset viewportOffset = ViewportOffset.zero();
     late TextSelection currentSelection;
     final RenderEditable editable = RenderEditable(
@@ -431,7 +433,7 @@ void main() {
       startHandleLayerLink: LayerLink(),
       endHandleLayerLink: LayerLink(),
       text: const TextSpan(
-        text: 'test\ntest',
+        text: text,
         style: TextStyle(
           height: 1.0, fontSize: 10.0, fontFamily: 'Ahem',
         ),
@@ -498,7 +500,9 @@ void main() {
   }, skip: isBrowser); // https://github.com/flutter/flutter/issues/61026
 
   test('selects correct place when offsets are flipped', () {
-    final TextSelectionDelegate delegate = FakeEditableTextState();
+    const String text = 'abc def ghi';
+    final TextSelectionDelegate delegate = FakeEditableTextState()
+      ..textEditingValue = const TextEditingValue(text: text);
     final ViewportOffset viewportOffset = ViewportOffset.zero();
     late TextSelection currentSelection;
     final RenderEditable editable = RenderEditable(
@@ -512,7 +516,7 @@ void main() {
         currentSelection = selection;
       },
       text: const TextSpan(
-        text: 'abc def ghi',
+        text: text,
         style: TextStyle(
           height: 1.0, fontSize: 10.0, fontFamily: 'Ahem',
         ),
@@ -534,9 +538,11 @@ void main() {
   test('selection does not flicker as user is dragging', () {
     int selectionChangedCount = 0;
     TextSelection? updatedSelection;
-    final TextSelectionDelegate delegate = FakeEditableTextState();
+    const String text = 'abc def ghi';
-    const TextSpan text = TextSpan(
+    final TextSelectionDelegate delegate = FakeEditableTextState()
-      text: 'abc def ghi',
+      ..textEditingValue = const TextEditingValue(text: text);
+    const TextSpan span = TextSpan(
+      text: text,
       style: TextStyle(
         height: 1.0, fontSize: 10.0, fontFamily: 'Ahem',
       ),
@@ -553,7 +559,7 @@ void main() {
       },
       startHandleLayerLink: LayerLink(),
       endHandleLayerLink: LayerLink(),
-      text: text,
+      text: span,
     );
 
     layout(editable1);
@@ -574,7 +580,7 @@ void main() {
         selectionChangedCount++;
         updatedSelection = selection;
       },
-      text: text,
+      text: span,
       startHandleLayerLink: LayerLink(),
       endHandleLayerLink: LayerLink(),
     );
@@ -933,8 +939,10 @@ void main() {
     expect(delegate.textEditingValue.text, '01232345');
   }, skip: isBrowser); // https://github.com/flutter/flutter/issues/61021
 
-  test('arrow keys and delete handle surrogate pairs correctly', () async {
+  test('arrow keys and delete handle surrogate pairs correctly case 2', () async {
-    final TextSelectionDelegate delegate = FakeEditableTextState();
+    const String text = '\u{1F44D}';
+    final TextSelectionDelegate delegate = FakeEditableTextState()
+      ..textEditingValue = const TextEditingValue(text: text);
     final ViewportOffset viewportOffset = ViewportOffset.zero();
     late TextSelection currentSelection;
     final RenderEditable editable = RenderEditable(
@@ -951,7 +959,7 @@ void main() {
       startHandleLayerLink: LayerLink(),
       endHandleLayerLink: LayerLink(),
       text: const TextSpan(
-        text: '\u{1F44D}',  // Thumbs up
+        text: text,  // Thumbs up
         style: TextStyle(
           height: 1.0, fontSize: 10.0, fontFamily: 'Ahem',
         ),
@@ -1038,7 +1046,9 @@ void main() {
   }, skip: isBrowser); // https://github.com/flutter/flutter/issues/61021
 
   test('arrow keys with selection text', () async {
-    final TextSelectionDelegate delegate = FakeEditableTextState();
+    const String text = '012345';
+    final TextSelectionDelegate delegate = FakeEditableTextState()
+      ..textEditingValue = const TextEditingValue(text: text);
     final ViewportOffset viewportOffset = ViewportOffset.zero();
     late TextSelection currentSelection;
     final RenderEditable editable = RenderEditable(
@@ -1055,7 +1065,7 @@ void main() {
       startHandleLayerLink: LayerLink(),
       endHandleLayerLink: LayerLink(),
       text: const TextSpan(
-        text: '012345',  // Thumbs up
+        text: text,  // Thumbs up
         style: TextStyle(height: 1.0, fontSize: 10.0, fontFamily: 'Ahem'),
       ),
       selection: const TextSelection.collapsed(
@@ -1096,7 +1106,9 @@ void main() {
   }, skip: isBrowser); // https://github.com/flutter/flutter/issues/58068
 
   test('arrow keys with selection text and shift', () async {
-    final TextSelectionDelegate delegate = FakeEditableTextState();
+    const String text = '012345';
+    final TextSelectionDelegate delegate = FakeEditableTextState()
+      ..textEditingValue = const TextEditingValue(text: text);
     final ViewportOffset viewportOffset = ViewportOffset.zero();
     late TextSelection currentSelection;
     final RenderEditable editable = RenderEditable(
@@ -1113,7 +1125,7 @@ void main() {
       startHandleLayerLink: LayerLink(),
       endHandleLayerLink: LayerLink(),
       text: const TextSpan(
-        text: '012345',  // Thumbs up
+        text: text,  // Thumbs up
         style: TextStyle(height: 1.0, fontSize: 10.0, fontFamily: 'Ahem'),
       ),
       selection: const TextSelection.collapsed(
@@ -1158,7 +1170,9 @@ void main() {
   }, skip: isBrowser); // https://github.com/flutter/flutter/issues/58068
 
   test('respects enableInteractiveSelection', () async {
-    final TextSelectionDelegate delegate = FakeEditableTextState();
+    const String text = '012345';
+    final TextSelectionDelegate delegate = FakeEditableTextState()
+      ..textEditingValue = const TextEditingValue(text: text);
     final ViewportOffset viewportOffset = ViewportOffset.zero();
     late TextSelection currentSelection;
     final RenderEditable editable = RenderEditable(
@@ -1175,7 +1189,7 @@ void main() {
       startHandleLayerLink: LayerLink(),
       endHandleLayerLink: LayerLink(),
       text: const TextSpan(
-        text: '012345',  // Thumbs up
+        text: text,  // Thumbs up
         style: TextStyle(height: 1.0, fontSize: 10.0, fontFamily: 'Ahem'),
       ),
       selection: const TextSelection.collapsed(