[go_router_builder] Fixes an deprecated warning for using withNullability (#9158)

*List which issues are fixed by this PR. You must list at least one issue.*
[Issue #166603](flutter/flutter#166603)

## Pre-Review Checklist

Author: raju-muliyashiya

packages/go_router_builder/CHANGELOG.md

@@ -1,3 +1,7 @@
+## 2.9.1
+
+- Fixes an deprecated warning for using withNullability
+
 ## 2.9.0
 
 - Adds support for `caseSensitive` for go routes.

packages/go_router_builder/lib/src/go_router_generator.dart

@@ -10,6 +10,7 @@ import 'package:build/build.dart';
 import 'package:source_gen/source_gen.dart';
 
 import 'route_config.dart';
+import 'type_helpers.dart';
 
 const String _routeDataUrl = 'package:go_router/src/route_data.dart';
 
@@ -79,7 +80,7 @@ ${getters.map((String e) => "$e,").join('\n')}
     ConstantReader annotation,
   ) {
     final String typedAnnotation =
-        annotation.objectValue.type!.getDisplayString(withNullability: false);
+        withoutNullability(annotation.objectValue.type!.getDisplayString());
     final String type =
         typedAnnotation.substring(0, typedAnnotation.indexOf('<'));
     final String routeData = _annotations[type]!;

packages/go_router_builder/lib/src/route_config.dart

@@ -172,6 +172,7 @@ class StatefulShellBranchConfig extends RouteBaseConfig {
 
   @override
   String get factorConstructorParameters => '';
+
   @override
   String get routeConstructorParameters =>
       '${navigatorKey == null ? '' : 'navigatorKey: $navigatorKey,'}'
@@ -616,7 +617,7 @@ abstract class RouteBaseConfig {
               return false;
             }
             final DartType typeArgument = typeArguments.single;
-            if (typeArgument.getDisplayString(withNullability: false) !=
+            if (withoutNullability(typeArgument.getDisplayString()) !=
                 'NavigatorState') {
               return false;
             }

packages/go_router_builder/lib/src/type_helpers.dart

@@ -68,7 +68,7 @@ String decodeParameter(ParameterElement element, Set<String> pathParameters) {
 
   throw InvalidGenerationSourceError(
     'The parameter type '
-    '`${paramType.getDisplayString(withNullability: false)}` is not supported.',
+    '`${withoutNullability(paramType.getDisplayString())}` is not supported.',
     element: element,
   );
 }
@@ -111,7 +111,7 @@ String enumMapName(InterfaceType type) => '_\$${type.element.name}EnumMap';
 String _stateValueAccess(ParameterElement element, Set<String> pathParameters) {
   if (element.isExtraField) {
     // ignore: avoid_redundant_argument_values
-    return 'extra as ${element.type.getDisplayString(withNullability: true)}';
+    return 'extra as ${element.type.getDisplayString()}';
   }
 
   late String access;
@@ -127,6 +127,16 @@ String _stateValueAccess(ParameterElement element, Set<String> pathParameters) {
   return access;
 }
 
+/// Returns `true` if the type string ends with a nullability marker (`?` or `*`)
+bool _isNullableType(String type) {
+  return type.endsWith('?') || type.endsWith('*');
+}
+
+/// Returns the type string without a trailing nullability marker
+String withoutNullability(String type) {
+  return _isNullableType(type) ? type.substring(0, type.length - 1) : type;
+}
+
 abstract class _TypeHelper {
   const _TypeHelper();
 

packages/go_router_builder/pubspec.yaml

@@ -2,7 +2,7 @@ name: go_router_builder
 description: >-
   A builder that supports generated strongly-typed route helpers for
   package:go_router
-version: 2.9.0
+version: 2.9.1
 repository: https://github.com/flutter/packages/tree/main/packages/go_router_builder
 issue_tracker: https://github.com/flutter/flutter/issues?q=is%3Aissue+is%3Aopen+label%3A%22p%3A+go_router_builder%22