[go_router_builder] Proposal: add json support, custom string encoder/decoder

packages/go_router/CHANGELOG.md

@@ -1,3 +1,7 @@
+## 15.2.1
+
+- Adds annotation for go_router_builder that enable custom string encoder/decoder [#110781](https://github.com/flutter/flutter/issues/110781). **Requires go_router_builder >= 3.0.1**.
+
 ## 15.2.0
 
 - `GoRouteData` now defines `.location`, `.go(context)`, `.push(context)`, `.pushReplacement(context)`, and `replace(context)` to be used for [Type-safe routing](https://pub.dev/documentation/go_router/latest/topics/Type-safe%20routes-topic.html). **Requires go_router_builder >= 3.0.0**.

packages/go_router/lib/go_router.dart

@@ -11,6 +11,7 @@ export 'src/configuration.dart';
 export 'src/delegate.dart';
 export 'src/information_provider.dart';
 export 'src/match.dart' hide RouteMatchListCodec;
+export 'src/misc/custom_parameter.dart';
 export 'src/misc/errors.dart';
 export 'src/misc/extensions.dart';
 export 'src/misc/inherited_router.dart';

packages/go_router/lib/src/misc/custom_parameter.dart

@@ -0,0 +1,40 @@
+// 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:meta/meta_meta.dart';
+
+/// annotation to define a custom parameter decoder/encoder
+/// this is useful when the is encoded/decoded in a non-standard way like base64
+/// this must be used as an annotation on a field
+/// ```dart
+/// String fromBase64(String value) {
+///   return const Utf8Decoder().convert(base64.decode(value));
+/// }
+/// String toBase64(String value) {
+///   return base64.encode(const Utf8Encoder().convert(value));
+/// }
+/// class MyRoute {
+///   @CustomParameterCodec(
+///     encode: toBase64,
+///     decode: fromBase64,
+///   )
+///   final String data;
+///   MyRoute(this.data);
+/// }
+/// ```
+@Target({TargetKind.field})
+class CustomParameterCodec {
+  /// create a custom parameter codec
+  ///
+  const CustomParameterCodec({
+    required this.encode,
+    required this.decode,
+  });
+
+  /// custom function to encode the field
+  final String Function(String json) encode;
+
+  /// custom function to decode the field
+  final String Function(String json) decode;
+}

packages/go_router/pubspec.yaml

@@ -1,7 +1,7 @@
 name: go_router
 description: A declarative router for Flutter based on Navigation 2 supporting
   deep linking, data-driven routes and more
-version: 15.2.0
+version: 15.2.1
 repository: https://github.com/flutter/packages/tree/main/packages/go_router
 issue_tracker: https://github.com/flutter/flutter/issues?q=is%3Aissue+is%3Aopen+label%3A%22p%3A+go_router%22
 

packages/go_router_builder/CHANGELOG.md

@@ -1,3 +1,8 @@
+## 3.0.1
+
+- Adds support for classes that support fromJson/toJson. [#117261](https://github.com/flutter/flutter/issues/117261)
+- Adds annotation that enable custom string encoder/decoder [#110781](https://github.com/flutter/flutter/issues/110781)
+
 ## 3.0.0
 
 - Route classes now required to use a mixin `with _$RouteName`.

packages/go_router_builder/example/lib/json_example.dart

@@ -0,0 +1,89 @@
+// 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.
+
+// ignore_for_file: public_member_api_docs, unreachable_from_main
+
+import 'dart:convert';
+
+import 'package:flutter/material.dart';
+import 'package:go_router/go_router.dart';
+
+import 'shared/data.dart';
+
+part 'json_example.g.dart';
+
+void main() => runApp(App());
+
+class App extends StatelessWidget {
+  App({super.key});
+
+  @override
+  Widget build(BuildContext context) => MaterialApp.router(
+        routerConfig: _router,
+        title: _appTitle,
+      );
+
+  final GoRouter _router = GoRouter(routes: $appRoutes);
+}
+
+@TypedGoRoute<HomeRoute>(
+  path: '/',
+  name: 'Home',
+  routes: <TypedGoRoute<GoRouteData>>[
+    TypedGoRoute<JsonRoute>(path: 'json'),
+  ],
+)
+class HomeRoute extends GoRouteData with _$HomeRoute {
+  const HomeRoute();
+
+  @override
+  Widget build(BuildContext context, GoRouterState state) => const HomeScreen();
+}
+
+class JsonRoute extends GoRouteData with _$JsonRoute {
+  const JsonRoute(this.json);
+
+  final JsonExample json;
+
+  @override
+  Widget build(BuildContext context, GoRouterState state) =>
+      JsonScreen(json: json);
+}
+
+class HomeScreen extends StatelessWidget {
+  const HomeScreen({super.key});
+
+  @override
+  Widget build(BuildContext context) => Scaffold(
+        appBar: AppBar(title: const Text(_appTitle)),
+        body: ListView(
+          children: <Widget>[
+            for (final JsonExample json in jsonData)
+              ListTile(
+                title: Text(json.name),
+                onTap: () => JsonRoute(json).go(context),
+              )
+          ],
+        ),
+      );
+}
+
+class JsonScreen extends StatelessWidget {
+  const JsonScreen({required this.json, super.key});
+  final JsonExample json;
+
+  @override
+  Widget build(BuildContext context) => Scaffold(
+        appBar: AppBar(title: Text(json.name)),
+        body: ListView(
+          key: ValueKey<String>(json.id),
+          children: <Widget>[
+            Text(json.id),
+            Text(json.name),
+          ],
+        ),
+      );
+}
+
+const String _appTitle = 'GoRouter Example: builder';

packages/go_router_builder/example/lib/shared/data.dart

@@ -191,3 +191,46 @@ class Repository {
     return FamilyPerson(family: family, person: family.person(pid));
   }
 }
+
+class JsonExample {
+  const JsonExample({required this.id, required this.name});
+
+  factory JsonExample.fromJson(Map<String, dynamic> json) {
+    return JsonExample(
+      id: json['id'] as String,
+      name: json['name'] as String,
+    );
+  }
+
+  Map<String, dynamic> toJson() {
+    return <String, dynamic>{
+      'id': id,
+      'name': name,
+    };
+  }
+
+  final String id;
+  final String name;
+}
+
+const List<JsonExample> jsonData = <JsonExample>[
+  JsonExample(id: '1', name: 'people'),
+  JsonExample(id: '2', name: 'animals'),
+];
+
+class JsonExampleNested<T> {
+  const JsonExampleNested({required this.child});
+
+  factory JsonExampleNested.fromJson(
+    Map<String, dynamic> json,
+    T Function(Object? json) fromJsonT,
+  ) {
+    return JsonExampleNested<T>(child: fromJsonT(json['child']));
+  }
+
+  Map<String, dynamic> toJson() {
+    return <String, dynamic>{'child': child};
+  }
+
+  final T child;
+}

packages/go_router_builder/lib/src/route_config.dart

@@ -303,7 +303,12 @@ class GoRouteConfig extends RouteBaseConfig {
         );
       }
     }
-    final String fromStateExpression = decodeParameter(element, _pathParams);
+    final List<ElementAnnotation>? metadata = _fieldMetadata(element.name);
+    final String fromStateExpression = decodeParameter(
+      element,
+      _pathParams,
+      metadata,
+    );
 
     if (element.isPositional) {
       return '$fromStateExpression,';
@@ -328,7 +333,8 @@ class GoRouteConfig extends RouteBaseConfig {
       );
     }
 
-    return encodeField(field);
+    final List<ElementAnnotation>? metadata = _fieldMetadata(fieldName);
+    return encodeField(field, metadata);
   }
 
   String get _locationQueryParams {
@@ -752,6 +758,10 @@ $routeDataClassName.$dataConvertionFunctionName(
   PropertyAccessorElement? _field(String name) =>
       routeDataClass.getGetter(name);
 
+  List<ElementAnnotation>? _fieldMetadata(String name) => routeDataClass.fields
+      .firstWhereOrNull((FieldElement element) => element.displayName == name)
+      ?.metadata;
+
   /// The name of `RouteData` subclass this configuration represents.
   @protected
   String get routeDataClassName;