packages/go_router/lib/src/builder.dart - mirrors/packages - Git at Google

 // Copyright 2013 The Flutter Authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.

 import 'package:flutter/widgets.dart';

 import 'configuration.dart';
 import 'delegate.dart';
 import 'logging.dart';
 import 'match.dart';
 import 'matching.dart';
 import 'misc/error_screen.dart';
 import 'pages/cupertino.dart';
 import 'pages/custom_transition_page.dart';
 import 'pages/material.dart';
 import 'route_data.dart';
 import 'typedefs.dart';

 /// Builds the top-level Navigator for GoRouter.
 class RouteBuilder {
   /// [RouteBuilder] constructor.
   RouteBuilder({
     required this.configuration,
     required this.builderWithNav,
     required this.errorPageBuilder,
     required this.errorBuilder,
     required this.restorationScopeId,
     required this.observers,
   });

   /// Builder function for a go router with Navigator.
   final GoRouterBuilderWithNav builderWithNav;

   /// Error page builder for the go router delegate.
   final GoRouterPageBuilder? errorPageBuilder;

   /// Error widget builder for the go router delegate.
   final GoRouterWidgetBuilder? errorBuilder;

   /// The route configuration for the app.
   final RouteConfiguration configuration;

   /// Restoration ID to save and restore the state of the navigator, including
   /// its history.
   final String? restorationScopeId;

   /// NavigatorObserver used to receive notifications when navigating in between routes.
   /// changes.
   final List<NavigatorObserver> observers;

   final GoRouterStateRegistry _registry = GoRouterStateRegistry();

   /// Builds the top-level Navigator for the given [RouteMatchList].
   Widget build(
     BuildContext context,
     RouteMatchList matchList,
     VoidCallback pop,
     bool routerNeglect,
   ) {
     if (matchList.isEmpty) {
       // The build method can be called before async redirect finishes. Build a
       // empty box until then.
       return const SizedBox.shrink();
     }
     return builderWithNav(
       context,
       Builder(
         builder: (BuildContext context) {
           try {
             final Map<Page<Object?>, GoRouterState> newRegistry =
                 <Page<Object?>, GoRouterState>{};
             final Widget result = tryBuild(context, matchList, pop,
                 routerNeglect, configuration.navigatorKey, newRegistry);
             _registry.updateRegistry(newRegistry);
             return GoRouterStateRegistryScope(
                 registry: _registry, child: result);
           } on _RouteBuilderError catch (e) {
             return _buildErrorNavigator(
                 context, e, matchList.uri, pop, configuration.navigatorKey);
           }
         },
       ),
     );
   }

   /// Builds the top-level Navigator by invoking the build method on each
   /// matching route.
   ///
   /// Throws a [_RouteBuilderError].
   @visibleForTesting
   Widget tryBuild(
     BuildContext context,
     RouteMatchList matchList,
     VoidCallback pop,
     bool routerNeglect,
     GlobalKey<NavigatorState> navigatorKey,
     Map<Page<Object?>, GoRouterState> registry,
   ) {
     return builderWithNav(
       context,
       _buildNavigator(
         pop,
         buildPages(
             context, matchList, pop, routerNeglect, navigatorKey, registry),
         navigatorKey,
         observers: observers,
       ),
     );
   }

   /// Returns the top-level pages instead of the root navigator. Used for
   /// testing.
   @visibleForTesting
   List<Page<Object?>> buildPages(
       BuildContext context,
       RouteMatchList matchList,
       VoidCallback onPop,
       bool routerNeglect,
       GlobalKey<NavigatorState> navigatorKey,
       Map<Page<Object?>, GoRouterState> registry) {
     try {
       final Map<GlobalKey<NavigatorState>, List<Page<Object?>>> keyToPage =
           <GlobalKey<NavigatorState>, List<Page<Object?>>>{};
       _buildRecursive(context, matchList, 0, onPop, routerNeglect, keyToPage,
           navigatorKey, registry);
       return keyToPage[navigatorKey]!;
     } on _RouteBuilderError catch (e) {
       return <Page<Object?>>[
         _buildErrorPage(context, e, matchList.uri),
       ];
     }
   }

   void _buildRecursive(
     BuildContext context,
     RouteMatchList matchList,
     int startIndex,
     VoidCallback pop,
     bool routerNeglect,
     Map<GlobalKey<NavigatorState>, List<Page<Object?>>> keyToPages,
     GlobalKey<NavigatorState> navigatorKey,
     Map<Page<Object?>, GoRouterState> registry,
   ) {
     if (startIndex >= matchList.matches.length) {
       return;
     }
     final RouteMatch match = matchList.matches[startIndex];

     if (match.error != null) {
       throw _RouteBuilderError('Match error found during build phase',
           exception: match.error);
     }

     final RouteBase route = match.route;
     final GoRouterState state = buildState(matchList, match);
     if (route is GoRoute) {
       final Page<Object?> page = _buildPageForRoute(context, state, match);
       registry[page] = state;
       // If this GoRoute is for a different Navigator, add it to the
       // list of out of scope pages
       final GlobalKey<NavigatorState> goRouteNavKey =
           route.parentNavigatorKey ?? navigatorKey;

       keyToPages.putIfAbsent(goRouteNavKey, () => <Page<Object?>>[]).add(page);

       _buildRecursive(context, matchList, startIndex + 1, pop, routerNeglect,
           keyToPages, navigatorKey, registry);
     } else if (route is ShellRoute) {
       // The key for the Navigator that will display this ShellRoute's page.
       final GlobalKey<NavigatorState> parentNavigatorKey = navigatorKey;

       // The key to provide to the ShellRoute's Navigator.
       final GlobalKey<NavigatorState> shellNavigatorKey = route.navigatorKey;

       // Add an entry for the parent navigator if none exists.
       keyToPages.putIfAbsent(parentNavigatorKey, () => <Page<Object?>>[]);

       // Add an entry for the shell route's navigator
       keyToPages.putIfAbsent(shellNavigatorKey, () => <Page<Object?>>[]);

       // Calling _buildRecursive can result in adding pages to the
       // parentNavigatorKey entry's list. Store the current length so
       // that the page for this ShellRoute is placed at the right index.
       final int shellPageIdx = keyToPages[parentNavigatorKey]!.length;

       // Build the remaining pages
       _buildRecursive(context, matchList, startIndex + 1, pop, routerNeglect,
           keyToPages, shellNavigatorKey, registry);

       // Build the Navigator
       final Widget child = _buildNavigator(
           pop, keyToPages[shellNavigatorKey]!, shellNavigatorKey);

       // Build the Page for this route
       final Page<Object?> page =
           _buildPageForRoute(context, state, match, child: child);
       registry[page] = state;
       // Place the ShellRoute's Page onto the list for the parent navigator.
       keyToPages
           .putIfAbsent(parentNavigatorKey, () => <Page<Object?>>[])
           .insert(shellPageIdx, page);
     }
   }

   Navigator _buildNavigator(
     VoidCallback pop,
     List<Page<Object?>> pages,
     Key? navigatorKey, {
     List<NavigatorObserver> observers = const <NavigatorObserver>[],
   }) {
     return Navigator(
       key: navigatorKey,
       restorationScopeId: restorationScopeId,
       pages: pages,
       observers: observers,
       onPopPage: (Route<dynamic> route, dynamic result) {
         if (!route.didPop(result)) {
           return false;
         }
         pop();
         return true;
       },
     );
   }

   /// Helper method that builds a [GoRouterState] object for the given [match]
   /// and [params].
   @visibleForTesting
   GoRouterState buildState(RouteMatchList matchList, RouteMatch match) {
     final RouteBase route = match.route;
     String? name;
     String path = '';
     if (route is GoRoute) {
       name = route.name;
       path = route.path;
     }
     final RouteMatchList effectiveMatchList =
         match is ImperativeRouteMatch ? match.matches : matchList;
     return GoRouterState(
       configuration,
       location: effectiveMatchList.uri.toString(),
       subloc: match.subloc,
       name: name,
       path: path,
       fullpath: effectiveMatchList.fullpath,
       params: effectiveMatchList.pathParameters,
       error: match.error,
       queryParams: effectiveMatchList.uri.queryParameters,
       queryParametersAll: effectiveMatchList.uri.queryParametersAll,
       extra: match.extra,
       pageKey: match.pageKey,
     );
   }

   /// Builds a [Page] for [StackedRoute]
   Page<Object?> _buildPageForRoute(
       BuildContext context, GoRouterState state, RouteMatch match,
       {Widget? child}) {
     final RouteBase route = match.route;
     Page<Object?>? page;

     if (route is GoRoute) {
       // Call the pageBuilder if it's non-null
       final GoRouterPageBuilder? pageBuilder = route.pageBuilder;
       if (pageBuilder != null) {
         page = pageBuilder(context, state);
       }
     } else if (route is ShellRoute) {
       final ShellRoutePageBuilder? pageBuilder = route.pageBuilder;
       assert(child != null, 'ShellRoute must contain a child route');
       if (pageBuilder != null) {
         page = pageBuilder(context, state, child!);
       }
     }

     if (page is NoOpPage) {
       page = null;
     }

     // Return the result of the route's builder() or pageBuilder()
     return page ??
         // Uses a Builder to make sure its rebuild scope is limited to the page.
         buildPage(context, state, Builder(builder: (BuildContext context) {
           return _callRouteBuilder(context, state, match, childWidget: child);
         }));
   }

   /// Calls the user-provided route builder from the [RouteMatch]'s [RouteBase].
   Widget _callRouteBuilder(
       BuildContext context, GoRouterState state, RouteMatch match,
       {Widget? childWidget}) {
     final RouteBase route = match.route;

     if (route == null) {
       throw _RouteBuilderError('No route found for match: $match');
     }

     if (route is GoRoute) {
       final GoRouterWidgetBuilder? builder = route.builder;

       if (builder == null) {
         throw _RouteBuilderError('No routeBuilder provided to GoRoute: $route');
       }

       return builder(context, state);
     } else if (route is ShellRoute) {
       if (childWidget == null) {
         throw _RouteBuilderException(
             'Attempt to build ShellRoute without a child widget');
       }

       final ShellRouteBuilder? builder = route.builder;

       if (builder == null) {
         throw _RouteBuilderError('No builder provided to ShellRoute: $route');
       }

       return builder(context, state, childWidget);
     }

     throw _RouteBuilderException('Unsupported route type $route');
   }

   _PageBuilderForAppType? _pageBuilderForAppType;

   Widget Function(
     BuildContext context,
     GoRouterState state,
   )? _errorBuilderForAppType;

   void _cacheAppType(BuildContext context) {
     // cache app type-specific page and error builders
     if (_pageBuilderForAppType == null) {
       assert(_errorBuilderForAppType == null);

       // can be null during testing
       final Element? elem = context is Element ? context : null;

       if (elem != null && isMaterialApp(elem)) {
         log.info('Using MaterialApp configuration');
         _pageBuilderForAppType = pageBuilderForMaterialApp;
         _errorBuilderForAppType =
             (BuildContext c, GoRouterState s) => MaterialErrorScreen(s.error);
       } else if (elem != null && isCupertinoApp(elem)) {
         log.info('Using CupertinoApp configuration');
         _pageBuilderForAppType = pageBuilderForCupertinoApp;
         _errorBuilderForAppType =
             (BuildContext c, GoRouterState s) => CupertinoErrorScreen(s.error);
       } else {
         log.info('Using WidgetsApp configuration');
         _pageBuilderForAppType = pageBuilderForWidgetApp;
         _errorBuilderForAppType =
             (BuildContext c, GoRouterState s) => ErrorScreen(s.error);
       }
     }

     assert(_pageBuilderForAppType != null);
     assert(_errorBuilderForAppType != null);
   }

   /// builds the page based on app type, i.e. MaterialApp vs. CupertinoApp
   @visibleForTesting
   Page<Object?> buildPage(
     BuildContext context,
     GoRouterState state,
     Widget child,
   ) {
     // build the page based on app type
     _cacheAppType(context);
     return _pageBuilderForAppType!(
       key: state.pageKey,
       name: state.name ?? state.fullpath,
       arguments: <String, String>{...state.params, ...state.queryParams},
       restorationId: state.pageKey.value,
       child: child,
     );
   }

   /// Builds a page without any transitions.
   Page<void> pageBuilderForWidgetApp({
     required LocalKey key,
     required String? name,
     required Object? arguments,
     required String restorationId,
     required Widget child,
   }) =>
       NoTransitionPage<void>(
         name: name,
         arguments: arguments,
         key: key,
         restorationId: restorationId,
         child: child,
       );

   /// Builds a Navigator containing an error page.
   Widget _buildErrorNavigator(BuildContext context, _RouteBuilderError e,
       Uri uri, VoidCallback pop, GlobalKey<NavigatorState> navigatorKey) {
     return _buildNavigator(
       pop,
       <Page<Object?>>[
         _buildErrorPage(context, e, uri),
       ],
       navigatorKey,
     );
   }

   /// Builds a an error page.
   Page<void> _buildErrorPage(
     BuildContext context,
     _RouteBuilderError error,
     Uri uri,
   ) {
     final GoRouterState state = GoRouterState(
       configuration,
       location: uri.toString(),
       subloc: uri.path,
       name: null,
       queryParams: uri.queryParameters,
       queryParametersAll: uri.queryParametersAll,
       error: Exception(error),
       pageKey: const ValueKey<String>('error'),
     );

     // If the error page builder is provided, use that, otherwise, if the error
     // builder is provided, wrap that in an app-specific page (for example,
     // MaterialPage). Finally, if nothing is provided, use a default error page
     // wrapped in the app-specific page.
     _cacheAppType(context);
     final GoRouterWidgetBuilder? errorBuilder = this.errorBuilder;
     return errorPageBuilder != null
         ? errorPageBuilder!(context, state)
         : buildPage(
             context,
             state,
             errorBuilder != null
                 ? errorBuilder(context, state)
                 : _errorBuilderForAppType!(context, state),
           );
   }
 }

 typedef _PageBuilderForAppType = Page<void> Function({
   required LocalKey key,
   required String? name,
   required Object? arguments,
   required String restorationId,
   required Widget child,
 });

 /// An error that occurred while building the app's UI based on the route
 /// matches.
 class _RouteBuilderError extends Error {
   /// Constructs a [_RouteBuilderError].
   _RouteBuilderError(this.message, {this.exception});

   /// The error message.
   final String message;

   /// The exception that occurred.
   final Exception? exception;

   @override
   String toString() {
     return '$message ${exception ?? ""}';
   }
 }

 /// An error that occurred while building the app's UI based on the route
 /// matches.
 class _RouteBuilderException implements Exception {
   /// Constructs a [_RouteBuilderException].
   //ignore: unused_element
   _RouteBuilderException(this.message, {this.exception});

   /// The error message.
   final String message;

   /// The exception that occurred.
   final Exception? exception;

   @override
   String toString() {
     return '$message ${exception ?? ""}';
   }
 }
	// Copyright 2013 The Flutter Authors. All rights reserved.
	// Use of this source code is governed by a BSD-style license that can be
	// found in the LICENSE file.

	import 'package:flutter/widgets.dart';

	import 'configuration.dart';
	import 'delegate.dart';
	import 'logging.dart';
	import 'match.dart';
	import 'matching.dart';
	import 'misc/error_screen.dart';
	import 'pages/cupertino.dart';
	import 'pages/custom_transition_page.dart';
	import 'pages/material.dart';
	import 'route_data.dart';
	import 'typedefs.dart';

	/// Builds the top-level Navigator for GoRouter.
	class RouteBuilder {
	/// [RouteBuilder] constructor.
	RouteBuilder({
	required this.configuration,
	required this.builderWithNav,
	required this.errorPageBuilder,
	required this.errorBuilder,
	required this.restorationScopeId,
	required this.observers,
	});

	/// Builder function for a go router with Navigator.
	final GoRouterBuilderWithNav builderWithNav;

	/// Error page builder for the go router delegate.
	final GoRouterPageBuilder? errorPageBuilder;

	/// Error widget builder for the go router delegate.
	final GoRouterWidgetBuilder? errorBuilder;

	/// The route configuration for the app.
	final RouteConfiguration configuration;

	/// Restoration ID to save and restore the state of the navigator, including
	/// its history.
	final String? restorationScopeId;

	/// NavigatorObserver used to receive notifications when navigating in between routes.
	/// changes.
	final List<NavigatorObserver> observers;

	final GoRouterStateRegistry _registry = GoRouterStateRegistry();

	/// Builds the top-level Navigator for the given [RouteMatchList].
	Widget build(
	BuildContext context,
	RouteMatchList matchList,
	VoidCallback pop,
	bool routerNeglect,
	) {
	if (matchList.isEmpty) {
	// The build method can be called before async redirect finishes. Build a
	// empty box until then.
	return const SizedBox.shrink();
	}
	return builderWithNav(
	context,
	Builder(
	builder: (BuildContext context) {
	try {
	final Map<Page<Object?>, GoRouterState> newRegistry =
	<Page<Object?>, GoRouterState>{};
	final Widget result = tryBuild(context, matchList, pop,
	routerNeglect, configuration.navigatorKey, newRegistry);
	_registry.updateRegistry(newRegistry);
	return GoRouterStateRegistryScope(
	registry: _registry, child: result);
	} on _RouteBuilderError catch (e) {
	return _buildErrorNavigator(
	context, e, matchList.uri, pop, configuration.navigatorKey);
	}
	},
	),
	);
	}

	/// Builds the top-level Navigator by invoking the build method on each
	/// matching route.
	///
	/// Throws a [_RouteBuilderError].
	@visibleForTesting
	Widget tryBuild(
	BuildContext context,
	RouteMatchList matchList,
	VoidCallback pop,
	bool routerNeglect,
	GlobalKey<NavigatorState> navigatorKey,
	Map<Page<Object?>, GoRouterState> registry,
	) {
	return builderWithNav(
	context,
	_buildNavigator(
	pop,
	buildPages(
	context, matchList, pop, routerNeglect, navigatorKey, registry),
	navigatorKey,
	observers: observers,
	),
	);
	}

	/// Returns the top-level pages instead of the root navigator. Used for
	/// testing.
	@visibleForTesting
	List<Page<Object?>> buildPages(
	BuildContext context,
	RouteMatchList matchList,
	VoidCallback onPop,
	bool routerNeglect,
	GlobalKey<NavigatorState> navigatorKey,
	Map<Page<Object?>, GoRouterState> registry) {
	try {
	final Map<GlobalKey<NavigatorState>, List<Page<Object?>>> keyToPage =
	<GlobalKey<NavigatorState>, List<Page<Object?>>>{};
	_buildRecursive(context, matchList, 0, onPop, routerNeglect, keyToPage,
	navigatorKey, registry);
	return keyToPage[navigatorKey]!;
	} on _RouteBuilderError catch (e) {
	return <Page<Object?>>[
	_buildErrorPage(context, e, matchList.uri),
	];
	}
	}

	void _buildRecursive(
	BuildContext context,
	RouteMatchList matchList,
	int startIndex,
	VoidCallback pop,
	bool routerNeglect,
	Map<GlobalKey<NavigatorState>, List<Page<Object?>>> keyToPages,
	GlobalKey<NavigatorState> navigatorKey,
	Map<Page<Object?>, GoRouterState> registry,
	) {
	if (startIndex >= matchList.matches.length) {
	return;
	}
	final RouteMatch match = matchList.matches[startIndex];

	if (match.error != null) {
	throw _RouteBuilderError('Match error found during build phase',
	exception: match.error);
	}

	final RouteBase route = match.route;
	final GoRouterState state = buildState(matchList, match);
	if (route is GoRoute) {
	final Page<Object?> page = _buildPageForRoute(context, state, match);
	registry[page] = state;
	// If this GoRoute is for a different Navigator, add it to the
	// list of out of scope pages
	final GlobalKey<NavigatorState> goRouteNavKey =
	route.parentNavigatorKey ?? navigatorKey;

	keyToPages.putIfAbsent(goRouteNavKey, () => <Page<Object?>>[]).add(page);

	_buildRecursive(context, matchList, startIndex + 1, pop, routerNeglect,
	keyToPages, navigatorKey, registry);
	} else if (route is ShellRoute) {
	// The key for the Navigator that will display this ShellRoute's page.
	final GlobalKey<NavigatorState> parentNavigatorKey = navigatorKey;

	// The key to provide to the ShellRoute's Navigator.
	final GlobalKey<NavigatorState> shellNavigatorKey = route.navigatorKey;

	// Add an entry for the parent navigator if none exists.
	keyToPages.putIfAbsent(parentNavigatorKey, () => <Page<Object?>>[]);

	// Add an entry for the shell route's navigator
	keyToPages.putIfAbsent(shellNavigatorKey, () => <Page<Object?>>[]);

	// Calling _buildRecursive can result in adding pages to the
	// parentNavigatorKey entry's list. Store the current length so
	// that the page for this ShellRoute is placed at the right index.
	final int shellPageIdx = keyToPages[parentNavigatorKey]!.length;

	// Build the remaining pages
	_buildRecursive(context, matchList, startIndex + 1, pop, routerNeglect,
	keyToPages, shellNavigatorKey, registry);

	// Build the Navigator
	final Widget child = _buildNavigator(
	pop, keyToPages[shellNavigatorKey]!, shellNavigatorKey);

	// Build the Page for this route
	final Page<Object?> page =
	_buildPageForRoute(context, state, match, child: child);
	registry[page] = state;
	// Place the ShellRoute's Page onto the list for the parent navigator.
	keyToPages
	.putIfAbsent(parentNavigatorKey, () => <Page<Object?>>[])
	.insert(shellPageIdx, page);
	}
	}

	Navigator _buildNavigator(
	VoidCallback pop,
	List<Page<Object?>> pages,
	Key? navigatorKey, {
	List<NavigatorObserver> observers = const <NavigatorObserver>[],
	}) {
	return Navigator(
	key: navigatorKey,
	restorationScopeId: restorationScopeId,
	pages: pages,
	observers: observers,
	onPopPage: (Route<dynamic> route, dynamic result) {
	if (!route.didPop(result)) {
	return false;
	}
	pop();
	return true;
	},
	);
	}

	/// Helper method that builds a [GoRouterState] object for the given [match]
	/// and [params].
	@visibleForTesting
	GoRouterState buildState(RouteMatchList matchList, RouteMatch match) {
	final RouteBase route = match.route;
	String? name;
	String path = '';
	if (route is GoRoute) {
	name = route.name;
	path = route.path;
	}
	final RouteMatchList effectiveMatchList =
	match is ImperativeRouteMatch ? match.matches : matchList;
	return GoRouterState(
	configuration,
	location: effectiveMatchList.uri.toString(),
	subloc: match.subloc,
	name: name,
	path: path,
	fullpath: effectiveMatchList.fullpath,
	params: effectiveMatchList.pathParameters,
	error: match.error,
	queryParams: effectiveMatchList.uri.queryParameters,
	queryParametersAll: effectiveMatchList.uri.queryParametersAll,
	extra: match.extra,
	pageKey: match.pageKey,
	);
	}

	/// Builds a [Page] for [StackedRoute]
	Page<Object?> _buildPageForRoute(
	BuildContext context, GoRouterState state, RouteMatch match,
	{Widget? child}) {
	final RouteBase route = match.route;
	Page<Object?>? page;

	if (route is GoRoute) {
	// Call the pageBuilder if it's non-null
	final GoRouterPageBuilder? pageBuilder = route.pageBuilder;
	if (pageBuilder != null) {
	page = pageBuilder(context, state);
	}
	} else if (route is ShellRoute) {
	final ShellRoutePageBuilder? pageBuilder = route.pageBuilder;
	assert(child != null, 'ShellRoute must contain a child route');
	if (pageBuilder != null) {
	page = pageBuilder(context, state, child!);
	}
	}

	if (page is NoOpPage) {
	page = null;
	}

	// Return the result of the route's builder() or pageBuilder()
	return page ??
	// Uses a Builder to make sure its rebuild scope is limited to the page.
	buildPage(context, state, Builder(builder: (BuildContext context) {
	return _callRouteBuilder(context, state, match, childWidget: child);
	}));
	}

	/// Calls the user-provided route builder from the [RouteMatch]'s [RouteBase].
	Widget _callRouteBuilder(
	BuildContext context, GoRouterState state, RouteMatch match,
	{Widget? childWidget}) {
	final RouteBase route = match.route;

	if (route == null) {
	throw _RouteBuilderError('No route found for match: $match');
	}

	if (route is GoRoute) {
	final GoRouterWidgetBuilder? builder = route.builder;

	if (builder == null) {
	throw _RouteBuilderError('No routeBuilder provided to GoRoute: $route');
	}

	return builder(context, state);
	} else if (route is ShellRoute) {
	if (childWidget == null) {
	throw _RouteBuilderException(
	'Attempt to build ShellRoute without a child widget');
	}

	final ShellRouteBuilder? builder = route.builder;

	if (builder == null) {
	throw _RouteBuilderError('No builder provided to ShellRoute: $route');
	}

	return builder(context, state, childWidget);
	}

	throw _RouteBuilderException('Unsupported route type $route');
	}

	_PageBuilderForAppType? _pageBuilderForAppType;

	Widget Function(
	BuildContext context,
	GoRouterState state,
	)? _errorBuilderForAppType;

	void _cacheAppType(BuildContext context) {
	// cache app type-specific page and error builders
	if (_pageBuilderForAppType == null) {
	assert(_errorBuilderForAppType == null);

	// can be null during testing
	final Element? elem = context is Element ? context : null;

	if (elem != null && isMaterialApp(elem)) {
	log.info('Using MaterialApp configuration');
	_pageBuilderForAppType = pageBuilderForMaterialApp;
	_errorBuilderForAppType =
	(BuildContext c, GoRouterState s) => MaterialErrorScreen(s.error);
	} else if (elem != null && isCupertinoApp(elem)) {
	log.info('Using CupertinoApp configuration');
	_pageBuilderForAppType = pageBuilderForCupertinoApp;
	_errorBuilderForAppType =
	(BuildContext c, GoRouterState s) => CupertinoErrorScreen(s.error);
	} else {
	log.info('Using WidgetsApp configuration');
	_pageBuilderForAppType = pageBuilderForWidgetApp;
	_errorBuilderForAppType =
	(BuildContext c, GoRouterState s) => ErrorScreen(s.error);
	}
	}

	assert(_pageBuilderForAppType != null);
	assert(_errorBuilderForAppType != null);
	}

	/// builds the page based on app type, i.e. MaterialApp vs. CupertinoApp
	@visibleForTesting
	Page<Object?> buildPage(
	BuildContext context,
	GoRouterState state,
	Widget child,
	) {
	// build the page based on app type
	_cacheAppType(context);
	return _pageBuilderForAppType!(
	key: state.pageKey,
	name: state.name ?? state.fullpath,
	arguments: <String, String>{...state.params, ...state.queryParams},
	restorationId: state.pageKey.value,
	child: child,
	);
	}

	/// Builds a page without any transitions.
	Page<void> pageBuilderForWidgetApp({
	required LocalKey key,
	required String? name,
	required Object? arguments,
	required String restorationId,
	required Widget child,
	}) =>
	NoTransitionPage<void>(
	name: name,
	arguments: arguments,
	key: key,
	restorationId: restorationId,
	child: child,
	);

	/// Builds a Navigator containing an error page.
	Widget _buildErrorNavigator(BuildContext context, _RouteBuilderError e,
	Uri uri, VoidCallback pop, GlobalKey<NavigatorState> navigatorKey) {
	return _buildNavigator(
	pop,
	<Page<Object?>>[
	_buildErrorPage(context, e, uri),
	],
	navigatorKey,
	);
	}

	/// Builds a an error page.
	Page<void> _buildErrorPage(
	BuildContext context,
	_RouteBuilderError error,
	Uri uri,
	) {
	final GoRouterState state = GoRouterState(
	configuration,
	location: uri.toString(),
	subloc: uri.path,
	name: null,
	queryParams: uri.queryParameters,
	queryParametersAll: uri.queryParametersAll,
	error: Exception(error),
	pageKey: const ValueKey<String>('error'),
	);

	// If the error page builder is provided, use that, otherwise, if the error
	// builder is provided, wrap that in an app-specific page (for example,
	// MaterialPage). Finally, if nothing is provided, use a default error page
	// wrapped in the app-specific page.
	_cacheAppType(context);
	final GoRouterWidgetBuilder? errorBuilder = this.errorBuilder;
	return errorPageBuilder != null
	? errorPageBuilder!(context, state)
	: buildPage(
	context,
	state,
	errorBuilder != null
	? errorBuilder(context, state)
	: _errorBuilderForAppType!(context, state),
	);
	}
	}

	typedef _PageBuilderForAppType = Page<void> Function({
	required LocalKey key,
	required String? name,
	required Object? arguments,
	required String restorationId,
	required Widget child,
	});

	/// An error that occurred while building the app's UI based on the route
	/// matches.
	class _RouteBuilderError extends Error {
	/// Constructs a [_RouteBuilderError].
	_RouteBuilderError(this.message, {this.exception});

	/// The error message.
	final String message;

	/// The exception that occurred.
	final Exception? exception;

	@override
	String toString() {
	return '$message ${exception ?? ""}';
	}
	}

	/// An error that occurred while building the app's UI based on the route
	/// matches.
	class _RouteBuilderException implements Exception {
	/// Constructs a [_RouteBuilderException].
	//ignore: unused_element
	_RouteBuilderException(this.message, {this.exception});

	/// The error message.
	final String message;

	/// The exception that occurred.
	final Exception? exception;

	@override
	String toString() {
	return '$message ${exception ?? ""}';
	}
	}