Normalize ThemeData.tabBarTheme (#156253)

Following #155476, this PR is to normalize `ThemeData.tabBarTheme`; change the `TabBarTheme tabBarTheme` property to `TabBarThemeData tabBarTheme` in `ThemeData`. In `ThemeData()` and `ThemeData.copyWith()`, the `tabBarTheme` parameter type is changed to `Object?` to accept both `TabBarTheme` and `TabBarThemeData` so that we won't cause immediate breaking change and make sure rolling is smooth. Once all component themes are normalized, these `Object?` types should be changed to `xxxThemeData`.

There's no way to create a dart fix because we can't add a "@deprecated" label for TabBarTheme; TabBarTheme is a new InheritedWidget subclass now.

Addresses the "theme normalization" sub project within #91772

Author: QuncCccccc

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

@@ -245,9 +245,9 @@ class TabBarTheme extends InheritedTheme with Diagnosticable {
   }
 
   /// Returns the closest [TabBarTheme] instance given the build context.
-  static TabBarTheme of(BuildContext context) {
+  static TabBarThemeData of(BuildContext context) {
     final TabBarTheme? tabBarTheme = context.dependOnInheritedWidgetOfExactType<TabBarTheme>();
-    return tabBarTheme ?? Theme.of(context).tabBarTheme;
+    return tabBarTheme?.data ?? Theme.of(context).tabBarTheme;
   }
 
   /// Linearly interpolate between two tab bar themes.

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

@@ -246,7 +246,7 @@ class _TabStyle extends AnimatedWidget {
 
   MaterialStateColor _resolveWithLabelColor(BuildContext context) {
     final ThemeData themeData = Theme.of(context);
-    final TabBarThemeData tabBarTheme = TabBarTheme.of(context).data;
+    final TabBarThemeData tabBarTheme = TabBarTheme.of(context);
     final Animation<double> animation = listenable as Animation<double>;
 
     // labelStyle.color (and tabBarTheme.labelStyle.color) is not considered
@@ -285,7 +285,7 @@ class _TabStyle extends AnimatedWidget {
 
   @override
   Widget build(BuildContext context) {
-    final TabBarThemeData tabBarTheme = TabBarTheme.of(context).data;
+    final TabBarThemeData tabBarTheme = TabBarTheme.of(context);
     final Animation<double> animation = listenable as Animation<double>;
 
     final Set<MaterialState> states = isSelected
@@ -1355,7 +1355,7 @@ class _TabBarState extends State<TabBar> {
 
   Decoration _getIndicator(TabBarIndicatorSize indicatorSize) {
     final ThemeData theme = Theme.of(context);
-    final TabBarThemeData tabBarTheme = TabBarTheme.of(context).data;
+    final TabBarThemeData tabBarTheme = TabBarTheme.of(context);
 
     if (widget.indicator != null) {
       return widget.indicator!;
@@ -1455,7 +1455,7 @@ class _TabBarState extends State<TabBar> {
 
   void _initIndicatorPainter() {
     final ThemeData theme = Theme.of(context);
-    final TabBarTheme tabBarTheme = TabBarTheme.of(context);
+    final TabBarThemeData tabBarTheme = TabBarTheme.of(context);
     final TabBarIndicatorSize indicatorSize = widget.indicatorSize
       ?? tabBarTheme.indicatorSize
       ?? _defaults.indicatorSize!;
@@ -1687,7 +1687,7 @@ class _TabBarState extends State<TabBar> {
     assert(debugCheckHasMaterialLocalizations(context));
     assert(_debugScheduleCheckHasValidTabsCount());
     final ThemeData theme = Theme.of(context);
-    final TabBarThemeData tabBarTheme = TabBarTheme.of(context).data;
+    final TabBarThemeData tabBarTheme = TabBarTheme.of(context);
     final TabAlignment effectiveTabAlignment = widget.tabAlignment ?? tabBarTheme.tabAlignment ?? _defaults.tabAlignment!;
     assert(_debugTabAlignmentIsValid(effectiveTabAlignment));
 

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

@@ -348,7 +348,8 @@ class ThemeData with Diagnosticable {
     SliderThemeData? sliderTheme,
     SnackBarThemeData? snackBarTheme,
     SwitchThemeData? switchTheme,
-    TabBarTheme? tabBarTheme,
+    // TODO(QuncCccccc): Change the parameter type to TabBarThemeData
+    Object? tabBarTheme,
     TextButtonThemeData? textButtonTheme,
     TextSelectionThemeData? textSelectionTheme,
     TimePickerThemeData? timePickerTheme,
@@ -541,7 +542,15 @@ class ThemeData with Diagnosticable {
     sliderTheme ??= const SliderThemeData();
     snackBarTheme ??= const SnackBarThemeData();
     switchTheme ??= const SwitchThemeData();
-    tabBarTheme ??= const TabBarTheme();
+    // TODO(QuncCccccc): Clean this up once the type of `tabBarTheme` is changed to `TabBarThemeData`
+    if (tabBarTheme != null) {
+      if (tabBarTheme is TabBarTheme) {
+        tabBarTheme = tabBarTheme.data;
+      } else if (tabBarTheme is! TabBarThemeData) {
+        throw ArgumentError('tabBarTheme must be either a TabBarThemeData or a TabBarTheme');
+      }
+    }
+    tabBarTheme ??= const TabBarThemeData();
     textButtonTheme ??= const TextButtonThemeData();
     textSelectionTheme ??= const TextSelectionThemeData();
     timePickerTheme ??= const TimePickerThemeData();
@@ -634,7 +643,7 @@ class ThemeData with Diagnosticable {
       sliderTheme: sliderTheme,
       snackBarTheme: snackBarTheme,
       switchTheme: switchTheme,
-      tabBarTheme: tabBarTheme,
+      tabBarTheme: tabBarTheme as TabBarThemeData,
       textButtonTheme: textButtonTheme,
       textSelectionTheme: textSelectionTheme,
       timePickerTheme: timePickerTheme,
@@ -1387,7 +1396,7 @@ class ThemeData with Diagnosticable {
   final SwitchThemeData switchTheme;
 
   /// A theme for customizing the size, shape, and color of the tab bar indicator.
-  final TabBarTheme tabBarTheme;
+  final TabBarThemeData tabBarTheme;
 
   /// A theme for customizing the appearance and internal layout of
   /// [TextButton]s.
@@ -1507,7 +1516,8 @@ class ThemeData with Diagnosticable {
     SliderThemeData? sliderTheme,
     SnackBarThemeData? snackBarTheme,
     SwitchThemeData? switchTheme,
-    TabBarTheme? tabBarTheme,
+    // TODO(QuncCccccc): Change the parameter type to TabBarThemeData
+    Object? tabBarTheme,
     TextButtonThemeData? textButtonTheme,
     TextSelectionThemeData? textSelectionTheme,
     TimePickerThemeData? timePickerTheme,
@@ -1547,6 +1557,15 @@ class ThemeData with Diagnosticable {
         throw ArgumentError('dialogTheme must be either a DialogThemeData or a DialogTheme');
       }
     }
+
+    // TODO(QuncCccccc): Clean this up once the type of `tabBarTheme` is changed to `TabBarThemeData`
+    if (tabBarTheme != null) {
+      if (tabBarTheme is TabBarTheme) {
+        tabBarTheme = tabBarTheme.data;
+      } else if (tabBarTheme is! TabBarThemeData) {
+        throw ArgumentError('tabBarTheme must be either a TabBarThemeData or a TabBarTheme');
+      }
+    }
     return ThemeData.raw(
       // For the sanity of the reader, make sure these properties are in the same
       // order in every place that they are separated by section comments (e.g.
@@ -1634,7 +1653,7 @@ class ThemeData with Diagnosticable {
       sliderTheme: sliderTheme ?? this.sliderTheme,
       snackBarTheme: snackBarTheme ?? this.snackBarTheme,
       switchTheme: switchTheme ?? this.switchTheme,
-      tabBarTheme: tabBarTheme ?? this.tabBarTheme,
+      tabBarTheme: tabBarTheme as TabBarThemeData? ?? this.tabBarTheme,
       textButtonTheme: textButtonTheme ?? this.textButtonTheme,
       textSelectionTheme: textSelectionTheme ?? this.textSelectionTheme,
       timePickerTheme: timePickerTheme ?? this.timePickerTheme,
@@ -1827,7 +1846,7 @@ class ThemeData with Diagnosticable {
       sliderTheme: SliderThemeData.lerp(a.sliderTheme, b.sliderTheme, t),
       snackBarTheme: SnackBarThemeData.lerp(a.snackBarTheme, b.snackBarTheme, t),
       switchTheme: SwitchThemeData.lerp(a.switchTheme, b.switchTheme, t),
-      tabBarTheme: TabBarTheme.lerp(a.tabBarTheme, b.tabBarTheme, t),
+      tabBarTheme: TabBarThemeData.lerp(a.tabBarTheme, b.tabBarTheme, t),
       textButtonTheme: TextButtonThemeData.lerp(a.textButtonTheme, b.textButtonTheme, t)!,
       textSelectionTheme: TextSelectionThemeData.lerp(a.textSelectionTheme, b.textSelectionTheme, t)!,
       timePickerTheme: TimePickerThemeData.lerp(a.timePickerTheme, b.timePickerTheme, t),
@@ -2125,7 +2144,7 @@ class ThemeData with Diagnosticable {
     properties.add(DiagnosticsProperty<SliderThemeData>('sliderTheme', sliderTheme, level: DiagnosticLevel.debug));
     properties.add(DiagnosticsProperty<SnackBarThemeData>('snackBarTheme', snackBarTheme, defaultValue: defaultData.snackBarTheme, level: DiagnosticLevel.debug));
     properties.add(DiagnosticsProperty<SwitchThemeData>('switchTheme', switchTheme, defaultValue: defaultData.switchTheme, level: DiagnosticLevel.debug));
-    properties.add(DiagnosticsProperty<TabBarTheme>('tabBarTheme', tabBarTheme, level: DiagnosticLevel.debug));
+    properties.add(DiagnosticsProperty<TabBarThemeData>('tabBarTheme', tabBarTheme, level: DiagnosticLevel.debug));
     properties.add(DiagnosticsProperty<TextButtonThemeData>('textButtonTheme', textButtonTheme, defaultValue: defaultData.textButtonTheme, level: DiagnosticLevel.debug));
     properties.add(DiagnosticsProperty<TextSelectionThemeData>('textSelectionTheme', textSelectionTheme, defaultValue: defaultData.textSelectionTheme, level: DiagnosticLevel.debug));
     properties.add(DiagnosticsProperty<TimePickerThemeData>('timePickerTheme', timePickerTheme, defaultValue: defaultData.timePickerTheme, level: DiagnosticLevel.debug));