Added AppBarTheme shape property (#86372)

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

@@ -472,7 +472,12 @@ class AppBar extends StatefulWidget implements PreferredSizeWidget {
   final Color? shadowColor;
 
   /// {@template flutter.material.appbar.shape}
-  /// The shape of the app bar's material's shape as well as its shadow.
+  /// The shape of the app bar's [Material] as well as its shadow.
+  ///
+  /// If this property is null, then [AppBarTheme.shape] of
+  /// [ThemeData.appBarTheme] is used.  Both properties default to null.
+  /// If both properties are null then the shape of the app bar's [Material]
+  /// is just a simple rectangle.
   ///
   /// A shadow is only displayed if the [elevation] is greater than
   /// zero.
@@ -1129,7 +1134,7 @@ class _AppBarState extends State<AppBar> {
           shadowColor: widget.shadowColor
             ?? appBarTheme.shadowColor
             ?? _defaultShadowColor,
-          shape: widget.shape,
+          shape: widget.shape ?? appBarTheme.shape,
           child: Semantics(
             explicitChildNodes: true,
             child: appBar,

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

@@ -38,6 +38,7 @@ class AppBarTheme with Diagnosticable {
     this.foregroundColor,
     this.elevation,
     this.shadowColor,
+    this.shape,
     this.iconTheme,
     this.actionsIconTheme,
     @Deprecated(
@@ -124,6 +125,10 @@ class AppBarTheme with Diagnosticable {
   /// descendant widgets.
   final Color? shadowColor;
 
+  /// Overrides the default value for [AppBar.shape] in all
+  /// descendant widgets.
+  final ShapeBorder? shape;
+
   /// Overrides the default value of [AppBar.iconTheme] in all
   /// descendant [AppBar] widgets.
   ///
@@ -229,6 +234,7 @@ class AppBarTheme with Diagnosticable {
     Color? foregroundColor,
     double? elevation,
     Color? shadowColor,
+    ShapeBorder? shape,
     IconThemeData? iconTheme,
     TextTheme? textTheme,
     bool? centerTitle,
@@ -249,6 +255,7 @@ class AppBarTheme with Diagnosticable {
       foregroundColor: foregroundColor ?? this.foregroundColor,
       elevation: elevation ?? this.elevation,
       shadowColor: shadowColor ?? this.shadowColor,
+      shape: shape ?? this.shape,
       iconTheme: iconTheme ?? this.iconTheme,
       actionsIconTheme: actionsIconTheme ?? this.actionsIconTheme,
       textTheme: textTheme ?? this.textTheme,
@@ -280,6 +287,7 @@ class AppBarTheme with Diagnosticable {
       foregroundColor: Color.lerp(a?.foregroundColor, b?.foregroundColor, t),
       elevation: lerpDouble(a?.elevation, b?.elevation, t),
       shadowColor: Color.lerp(a?.shadowColor, b?.shadowColor, t),
+      shape: ShapeBorder.lerp(a?.shape, b?.shape, t),
       iconTheme: IconThemeData.lerp(a?.iconTheme, b?.iconTheme, t),
       actionsIconTheme: IconThemeData.lerp(a?.actionsIconTheme, b?.actionsIconTheme, t),
       textTheme: TextTheme.lerp(a?.textTheme, b?.textTheme, t),
@@ -301,6 +309,7 @@ class AppBarTheme with Diagnosticable {
       foregroundColor,
       elevation,
       shadowColor,
+      shape,
       iconTheme,
       actionsIconTheme,
       textTheme,
@@ -326,6 +335,7 @@ class AppBarTheme with Diagnosticable {
         && other.foregroundColor == foregroundColor
         && other.elevation == elevation
         && other.shadowColor == shadowColor
+        && other.shape == shape
         && other.iconTheme == iconTheme
         && other.actionsIconTheme == actionsIconTheme
         && other.textTheme == textTheme
@@ -346,6 +356,7 @@ class AppBarTheme with Diagnosticable {
     properties.add(ColorProperty('foregroundColor', foregroundColor, defaultValue: null));
     properties.add(DiagnosticsProperty<double>('elevation', elevation, defaultValue: null));
     properties.add(ColorProperty('shadowColor', shadowColor, defaultValue: null));
+    properties.add(DiagnosticsProperty<ShapeBorder>('shape', shape, defaultValue: null));
     properties.add(DiagnosticsProperty<IconThemeData>('iconTheme', iconTheme, defaultValue: null));
     properties.add(DiagnosticsProperty<IconThemeData>('actionsIconTheme', actionsIconTheme, defaultValue: null));
     properties.add(DiagnosticsProperty<TextTheme>('textTheme', textTheme, defaultValue: null));

packages/flutter/test/material/app_bar_theme_test.dart

@@ -37,6 +37,7 @@ void main() {
     expect(widget.color, Colors.blue);
     expect(widget.elevation, 4.0);
     expect(widget.shadowColor, Colors.black);
+    expect(widget.shape, null);
     expect(iconTheme.data, const IconThemeData(color: Colors.white));
     expect(actionsIconTheme.data, const IconThemeData(color: Colors.white));
     expect(actionIconText.text.style!.color, Colors.white);
@@ -72,6 +73,7 @@ void main() {
     expect(widget.color, appBarTheme.backgroundColor);
     expect(widget.elevation, appBarTheme.elevation);
     expect(widget.shadowColor, appBarTheme.shadowColor);
+    expect(widget.shape, const StadiumBorder());
     expect(iconTheme.data, appBarTheme.iconTheme);
     expect(actionsIconTheme.data, appBarTheme.actionsIconTheme);
     expect(actionIconText.text.style!.color, appBarTheme.actionsIconTheme!.color);
@@ -131,6 +133,7 @@ void main() {
     const Color color = Colors.orange;
     const double elevation = 3.0;
     const Color shadowColor = Colors.red;
+    const ShapeBorder shape = RoundedRectangleBorder();
     const IconThemeData iconThemeData = IconThemeData(color: Colors.green);
     const IconThemeData actionsIconThemeData = IconThemeData(color: Colors.lightBlue);
     const TextStyle toolbarTextStyle = TextStyle(color: Colors.pink);
@@ -138,7 +141,9 @@ void main() {
 
     await tester.pumpWidget(
       MaterialApp(
-        theme: ThemeData.from(colorScheme: const ColorScheme.light()),
+        theme: ThemeData.from(colorScheme: const ColorScheme.light()).copyWith(
+          appBarTheme: _appBarTheme(),
+        ),
         home: Scaffold(
           appBar: AppBar(
             backgroundColor: color,
@@ -146,6 +151,7 @@ void main() {
             systemOverlayStyle: systemOverlayStyle,
             elevation: elevation,
             shadowColor: shadowColor,
+            shape: shape,
             iconTheme: iconThemeData,
             actionsIconTheme: actionsIconThemeData,
             toolbarTextStyle: toolbarTextStyle,
@@ -168,6 +174,7 @@ void main() {
     expect(widget.color, color);
     expect(widget.elevation, elevation);
     expect(widget.shadowColor, shadowColor);
+    expect(widget.shape, shape);
     expect(iconTheme.data, iconThemeData);
     expect(actionsIconTheme.data, actionsIconThemeData);
     expect(actionIconText.text.style!.color, actionsIconThemeData.color);
@@ -525,6 +532,7 @@ AppBarTheme _appBarTheme() {
     backgroundColor: backgroundColor,
     elevation: elevation,
     shadowColor: shadowColor,
+    shape: StadiumBorder(),
     iconTheme: iconThemeData,
     toolbarHeight: 96,
     toolbarTextStyle: TextStyle(color: Colors.yellow),