[A11y] TextField prefix icon and suffix icon create a sibling node' (flutter#173312)

prefix/suffix icon should have their own merge group. 

Noted a textfield can have suffix and suffix icon the same time so they
should be different merge group.

Co-authored-by: chunhtai <47866232+chunhtai@users.noreply.github.com>

Author: hannah-hyj

packages/flutter/lib/src/material/input_decorator.dart

@@ -13,6 +13,7 @@ library;
 import 'dart:math' as math;
 import 'dart:ui' show lerpDouble;
 
+import 'package:collection/collection.dart';
 import 'package:flutter/foundation.dart';
 import 'package:flutter/rendering.dart';
 import 'package:flutter/widgets.dart';
@@ -1685,25 +1686,28 @@ class _RenderDecoration extends RenderBox
   ) {
     final ChildSemanticsConfigurationsResultBuilder builder =
         ChildSemanticsConfigurationsResultBuilder();
-    List<SemanticsConfiguration>? prefixMergeGroup;
-    List<SemanticsConfiguration>? suffixMergeGroup;
+
+    final Map<SemanticsTag, List<SemanticsConfiguration>> mergeGroups =
+        <SemanticsTag, List<SemanticsConfiguration>>{};
+    final Set<SemanticsTag> tags = <SemanticsTag>{
+      _InputDecoratorState._kPrefixSemanticsTag,
+      _InputDecoratorState._kPrefixIconSemanticsTag,
+      _InputDecoratorState._kSuffixSemanticsTag,
+      _InputDecoratorState._kSuffixIconSemanticsTag,
+    };
+
     for (final SemanticsConfiguration childConfig in childConfigs) {
-      if (childConfig.tagsChildrenWith(_InputDecoratorState._kPrefixSemanticsTag)) {
-        prefixMergeGroup ??= <SemanticsConfiguration>[];
-        prefixMergeGroup.add(childConfig);
-      } else if (childConfig.tagsChildrenWith(_InputDecoratorState._kSuffixSemanticsTag)) {
-        suffixMergeGroup ??= <SemanticsConfiguration>[];
-        suffixMergeGroup.add(childConfig);
+      final SemanticsTag? tag = tags.firstWhereOrNull(
+        (SemanticsTag tag) => childConfig.tagsChildrenWith(tag),
+      );
+      if (tag != null) {
+        mergeGroups.putIfAbsent(tag, () => <SemanticsConfiguration>[]).add(childConfig);
       } else {
         builder.markAsMergeUp(childConfig);
       }
     }
-    if (prefixMergeGroup != null) {
-      builder.markAsSiblingMergeGroup(prefixMergeGroup);
-    }
-    if (suffixMergeGroup != null) {
-      builder.markAsSiblingMergeGroup(suffixMergeGroup);
-    }
+
+    mergeGroups.values.forEach(builder.markAsSiblingMergeGroup);
     return builder.build();
   }
 
@@ -1985,7 +1989,13 @@ class _InputDecoratorState extends State<InputDecorator> with TickerProviderStat
     name: hashCode.toString(),
   );
   static const SemanticsTag _kPrefixSemanticsTag = SemanticsTag('_InputDecoratorState.prefix');
+  static const SemanticsTag _kPrefixIconSemanticsTag = SemanticsTag(
+    '_InputDecoratorState.prefixIcon',
+  );
   static const SemanticsTag _kSuffixSemanticsTag = SemanticsTag('_InputDecoratorState.suffix');
+  static const SemanticsTag _kSuffixIconSemanticsTag = SemanticsTag(
+    '_InputDecoratorState.suffixIcon',
+  );
 
   @override
   void initState() {
@@ -2466,7 +2476,10 @@ class _InputDecoratorState extends State<InputDecorator> with TickerProviderStat
                         iconSize: WidgetStatePropertyAll<double>(iconSize),
                       ).merge(iconButtonTheme.style),
                     ),
-                    child: Semantics(child: decoration.prefixIcon),
+                    child: Semantics(
+                      tagForChildren: _kPrefixIconSemanticsTag,
+                      child: decoration.prefixIcon,
+                    ),
                   ),
                 ),
               ),
@@ -2503,7 +2516,10 @@ class _InputDecoratorState extends State<InputDecorator> with TickerProviderStat
                         iconSize: WidgetStatePropertyAll<double>(iconSize),
                       ).merge(iconButtonTheme.style),
                     ),
-                    child: Semantics(child: decoration.suffixIcon),
+                    child: Semantics(
+                      tagForChildren: _kSuffixIconSemanticsTag,
+                      child: decoration.suffixIcon,
+                    ),
                   ),
                 ),
               ),

packages/flutter/test/material/text_field_test.dart

@@ -5675,6 +5675,48 @@ void main() {
     semantics.dispose();
   });
 
+  testWidgets('TextField prefix icon and suffix icon create a sibling node', (
+    WidgetTester tester,
+  ) async {
+    final SemanticsTester semantics = SemanticsTester(tester);
+    await tester.pumpWidget(
+      overlay(
+        child: TextField(
+          controller: _textEditingController(text: 'some text'),
+          decoration: const InputDecoration(prefixIcon: Text('Prefix'), suffixIcon: Text('Suffix')),
+        ),
+      ),
+    );
+
+    expect(
+      semantics,
+      hasSemantics(
+        TestSemantics.root(
+          children: <TestSemantics>[
+            TestSemantics.rootChild(
+              id: 1,
+              textDirection: TextDirection.ltr,
+              value: 'some text',
+              actions: <SemanticsAction>[SemanticsAction.tap, SemanticsAction.focus],
+              inputType: ui.SemanticsInputType.text,
+              currentValueLength: 9,
+              flags: <SemanticsFlag>[
+                SemanticsFlag.isTextField,
+                SemanticsFlag.hasEnabledState,
+                SemanticsFlag.isEnabled,
+              ],
+            ),
+            TestSemantics.rootChild(id: 2, textDirection: TextDirection.ltr, label: 'Prefix'),
+            TestSemantics.rootChild(id: 3, textDirection: TextDirection.ltr, label: 'Suffix'),
+          ],
+        ),
+        ignoreTransform: true,
+        ignoreRect: true,
+      ),
+    );
+    semantics.dispose();
+  });
+
   testWidgets('TextField with specified suffixStyle', (WidgetTester tester) async {
     final TextStyle suffixStyle = TextStyle(color: Colors.pink[500], fontSize: 10.0);