Fix TabController throws build scheduled during frame error (#105442)

Author: bleroux

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

@@ -1495,15 +1495,13 @@ class _TabBarViewState extends State<TabBarView> {
     }
 
     final Duration duration = _controller!.animationDuration;
-
-    if (duration == Duration.zero) {
-      _pageController.jumpToPage(_currentIndex!);
-      return Future<void>.value();
-    }
-
     final int previousIndex = _controller!.previousIndex;
 
     if ((_currentIndex! - previousIndex).abs() == 1) {
+      if (duration == Duration.zero) {
+        _pageController.jumpToPage(_currentIndex!);
+        return Future<void>.value();
+      }
       _warpUnderwayCount += 1;
       await _pageController.animateToPage(_currentIndex!, duration: duration, curve: Curves.ease);
       _warpUnderwayCount -= 1;
@@ -1525,6 +1523,11 @@ class _TabBarViewState extends State<TabBarView> {
     });
     _pageController.jumpToPage(initialPage);
 
+    if (duration == Duration.zero) {
+      _pageController.jumpToPage(_currentIndex!);
+      return Future<void>.value();
+    }
+
     await _pageController.animateToPage(_currentIndex!, duration: duration, curve: Curves.ease);
     if (!mounted) {
       return Future<void>.value();

packages/flutter/test/material/tabs_test.dart

@@ -1191,6 +1191,51 @@ void main() {
     expect(controller.indexIsChanging, false);
   });
 
+  testWidgets('TabBar should not throw when animation is disabled in controller', (WidgetTester tester) async {
+    // Regression test for https://github.com/flutter/flutter/issues/102600
+    final List<String> tabs = <String>['A'];
+
+    Widget buildWithTabBarView() {
+      return boilerplate(
+        child: DefaultTabController(
+          animationDuration: Duration.zero,
+          length: tabs.length,
+          child: Column(
+            children: <Widget>[
+              TabBar(
+                tabs: tabs.map<Widget>((String tab) => Tab(text: tab)).toList(),
+                isScrollable: true,
+              ),
+              Flexible(
+                child: TabBarView(
+                  children: List<Widget>.generate(
+                    tabs.length,
+                    (int index) => Text('Tab $index'),
+                  ),
+                ),
+              ),
+            ],
+          ),
+        ),
+      );
+    }
+
+    await tester.pumpWidget(buildWithTabBarView());
+    TabController controller = DefaultTabController.of(tester.element(find.text('A')))!;
+    expect(controller.index, 0);
+
+    tabs.add('B');
+    await tester.pumpWidget(buildWithTabBarView());
+    tabs.add('C');
+    await tester.pumpWidget(buildWithTabBarView());
+    await tester.tap(find.text('C'));
+    await tester.pumpAndSettle();
+    controller = DefaultTabController.of(tester.element(find.text('A')))!;
+    expect(controller.index, 2);
+
+    expect(tester.takeException(), isNull);
+  });
+
   testWidgets('TabBarView skips animation when disabled in controller', (WidgetTester tester) async {
     final List<String> tabs = <String>['A', 'B', 'C'];
     final TabController tabController = TabController(