Fixes router to not report route information when it is already up to… (#64596)

packages/flutter/lib/src/widgets/router.dart

@@ -395,7 +395,6 @@ class _RouterState<T> extends State<Router<T>> {
     if (widget.routeInformationProvider != null) {
       _processInitialRoute();
     }
-    _lastSeenLocation = widget.routeInformationProvider?.value?.location;
   }
 
   bool _routeInformationReportingTaskScheduled = false;
@@ -552,6 +551,7 @@ class _RouterState<T> extends State<Router<T>> {
   void _processInitialRoute() {
     _currentRouteInformationParserTransaction = Object();
     _currentRouterDelegateTransaction = Object();
+    _lastSeenLocation = widget.routeInformationProvider.value.location;
     widget.routeInformationParser
       .parseRouteInformation(widget.routeInformationProvider.value)
       .then<T>(_verifyRouteInformationParserStillCurrent(_currentRouteInformationParserTransaction, widget))
@@ -563,6 +563,7 @@ class _RouterState<T> extends State<Router<T>> {
   void _handleRouteInformationProviderNotification() {
     _currentRouteInformationParserTransaction = Object();
     _currentRouterDelegateTransaction = Object();
+    _lastSeenLocation = widget.routeInformationProvider.value.location;
     widget.routeInformationParser
       .parseRouteInformation(widget.routeInformationProvider.value)
       .then<T>(_verifyRouteInformationParserStillCurrent(_currentRouteInformationParserTransaction, widget))

packages/flutter/test/widgets/router_test.dart

@@ -434,6 +434,45 @@ void main() {
     expect(reportedRouteInformation.location, 'update');
   });
 
+  testWidgets('router does not report when route information is up to date with route information provider', (WidgetTester tester) async {
+    RouteInformation reportedRouteInformation;
+    final SimpleRouteInformationProvider provider = SimpleRouteInformationProvider(
+      onRouterReport: (RouteInformation information) {
+        reportedRouteInformation = information;
+      }
+    );
+    provider.value = const RouteInformation(
+      location: 'initial',
+    );
+    final SimpleRouterDelegate delegate = SimpleRouterDelegate(reportConfiguration: true);
+    delegate.builder = (BuildContext context, RouteInformation routeInformation) {
+      return Text(routeInformation.location);
+    };
+
+    await tester.pumpWidget(buildBoilerPlate(
+      Router<RouteInformation>(
+        routeInformationProvider: provider,
+        routeInformationParser: SimpleRouteInformationParser(),
+        routerDelegate: delegate,
+      )
+    ));
+    expect(find.text('initial'), findsOneWidget);
+    expect(reportedRouteInformation, isNull);
+    // This will cause the router to rebuild.
+    provider.value = const RouteInformation(
+      location: 'update',
+    );
+    // This will schedule the route reporting.
+    delegate.notifyListeners();
+    await tester.pump();
+
+    expect(find.text('initial'), findsNothing);
+    expect(find.text('update'), findsOneWidget);
+    // The router should not report because the route name is already up to
+    // date.
+    expect(reportedRouteInformation, isNull);
+  });
+
   testWidgets('PlatformRouteInformationProvider works', (WidgetTester tester) async {
     final RouteInformationProvider provider = PlatformRouteInformationProvider(
       initialRouteInformation: const RouteInformation(