Add borderRadius property to PopupMenuButton (#151228)

This PR is adding borderRadius property to PopupMenuButton. PopupMenuButton has a child wrapped in an InkWell widget where as of right now you can't customize it's border radius resulting in wrong splash effect when the child has border radius.

Fixes: #151227 

https://github.com/flutter/flutter/assets/20647774/93feb0a4-c4ff-4059-bde2-e59c4d35e2b6

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

@@ -1196,6 +1196,7 @@ class PopupMenuButton<T> extends StatefulWidget {
     this.padding = const EdgeInsets.all(8.0),
     this.menuPadding,
     this.child,
+    this.borderRadius,
     this.splashRadius,
     this.icon,
     this.iconSize,
@@ -1292,6 +1293,11 @@ class PopupMenuButton<T> extends StatefulWidget {
   /// and the button will utilize an [InkWell] for taps.
   final Widget? child;
 
+  /// The border radius for the [InkWell] that wraps the [child].
+  ///
+  /// Defaults to null, which indicates no border radius should be applied.
+  final BorderRadius? borderRadius;
+
   /// If provided, the [icon] is used for this button
   /// and the button will behave like an [IconButton].
   final Widget? icon;
@@ -1527,6 +1533,7 @@ class PopupMenuButtonState<T> extends State<PopupMenuButton<T>> {
       return Tooltip(
         message: widget.tooltip ?? MaterialLocalizations.of(context).showMenuTooltip,
         child: InkWell(
+          borderRadius: widget.borderRadius,
           onTap: widget.enabled ? showButtonMenu : null,
           canRequestFocus: _canRequestFocus,
           radius: widget.splashRadius,

packages/flutter/test/material/popup_menu_test.dart

@@ -4242,6 +4242,49 @@ void main() {
     ));
     expect(iconText.text.style?.color, Colors.red);
   });
+
+  testWidgets("Popup menu child's InkWell borderRadius", (WidgetTester tester) async {
+    final BorderRadius borderRadius = BorderRadius.circular(20);
+
+    Widget buildPopupMenu({required BorderRadius? borderRadius}) {
+      return MaterialApp(
+        home: Scaffold(
+          body: Center(
+            child: PopupMenuButton<String>(
+              borderRadius: borderRadius,
+              itemBuilder: (_) => <PopupMenuEntry<String>>[
+                const PopupMenuItem<String>(
+                  value: 'value',
+                  child: Text('Item 0'),
+                ),
+              ],
+              child: const Row(
+                mainAxisSize: MainAxisSize.min,
+                children: <Widget>[
+                  Text('Pop up menu'),
+                  Icon(Icons.arrow_drop_down),
+                ],
+              ),
+            ),
+          ),
+        ),
+      );
+    }
+
+    // Popup menu with default null borderRadius.
+    await tester.pumpWidget(buildPopupMenu(borderRadius: null));
+    await tester.pumpAndSettle();
+
+    InkWell inkWell = tester.widget<InkWell>(find.byType(InkWell));
+    expect(inkWell.borderRadius, isNull);
+
+    // Popup menu with fixed borderRadius.
+    await tester.pumpWidget(buildPopupMenu(borderRadius: borderRadius));
+    await tester.pumpAndSettle();
+
+    inkWell = tester.widget<InkWell>(find.byType(InkWell));
+    expect(inkWell.borderRadius, borderRadius);
+  });
 }
 
 Matcher overlaps(Rect other) => OverlapsMatcher(other);