[native_assets_cli] Introduce JsonObject base class for syntax (#2159)

Author: dcharkes

pkgs/json_syntax_generator/lib/src/generator/helper_library.dart

@@ -6,6 +6,20 @@
 ///
 /// This simplifies the code generator.
 const helperLib = r'''
+class JsonObject {
+  final Map<String, Object?> json;
+
+  final List<Object> path;
+
+  JsonReader get _reader => JsonReader(json, path);
+
+  JsonObject() : json = {}, path = const [];
+
+  JsonObject.fromJson(this.json, {this.path = const []});
+
+  List<String> validate() => [];
+}
+
 class JsonReader {
   /// The JSON Object this reader is reading.
   final Map<String, Object?> json;

pkgs/json_syntax_generator/lib/src/generator/normal_class_generator.dart

@@ -20,15 +20,12 @@ class ClassGenerator {
 
   void _generateClass(StringBuffer buffer) {
     final className = classInfo.name;
-    final superclassName = classInfo.superclass?.name;
+    final superclassName = classInfo.superclass?.name ?? 'JsonObject';
 
-    final extendsString =
-        superclassName != null ? 'extends $superclassName' : '';
     buffer.writeln('''
-class $className $extendsString {
+class $className extends $superclassName {
 ''');
     buffer.writeln(_generateTag());
-    buffer.writeln(_generateFields());
     buffer.writeln(_generateJsonFactory());
     buffer.writeln(_generateJsonConstructor());
     buffer.writeln(_generateDefaultConstructor());
@@ -52,21 +49,6 @@ static const ${tagProperty}Value = '$tagValue';
 ''';
   }
 
-  String _generateFields() {
-    if (classInfo.superclass != null) {
-      // The super class already has the required fields.
-      return '';
-    }
-
-    return '''
-  final Map<String, Object?> json;
-
-  final List<Object> path;
-
-  JsonReader get _reader => JsonReader(json, path);
-''';
-  }
-
   /// If this is the parent class in a tagged union, generate a factory that
   /// branches to invoke subclass constructors.
   String _generateJsonFactory() {
@@ -106,9 +88,9 @@ static const ${tagProperty}Value = '$tagValue';
       final constructorName =
           classInfo.isTaggedUnion ? '_fromJson' : 'fromJson';
       return '''
-  $className.$constructorName(this.json, {
-    this.path = const [],
-  });
+  $className.$constructorName(super.json, {
+    super.path = const [],
+  }) : super.fromJson();
 ''';
     }
 
@@ -133,8 +115,7 @@ static const ${tagProperty}Value = '$tagValue';
     if (classInfo.superclass == null) {
       return '''
   $className($parametersString)
-  : json = {},
-    path = const []
+  : super()
     $body
 ''';
     }
@@ -260,14 +241,6 @@ static const ${tagProperty}Value = '$tagValue';
     ];
     final validateCallsString = validateCalls.join(',\n');
 
-    if (classInfo.superclass == null) {
-      return '''
-  List<String> validate() => [
-    $validateCallsString
-  ];
-''';
-    }
-
     return '''
   @override
   List<String> validate() => [

pkgs/json_syntax_generator/lib/src/model/dart_type.dart

@@ -55,6 +55,9 @@ class ClassDartType extends DartType {
   String toNonNullableString() => classInfo.name;
 }
 
+/// The [ClassInfo] for the `JsonObject` base class.
+final jsonObjectClassInfo = NormalClassInfo(name: 'JsonObject', properties: []);
+
 class ListDartType extends DartType {
   final DartType itemType;
 

pkgs/json_syntax_generator/lib/src/parser/schema_analyzer.dart

@@ -365,8 +365,8 @@ class SchemaAnalyzer {
                   'Expected an object with arbitrary properties.',
                 );
               }
-              dartType = MapDartType(
-                valueType: const ObjectDartType(isNullable: true),
+              dartType = ClassDartType(
+                classInfo: jsonObjectClassInfo,
                 isNullable: !required,
               );
             default:

pkgs/native_assets_cli/lib/src/code_assets/config.dart

@@ -206,7 +206,7 @@ extension CodeAssetBuildInputBuilder on HookConfigBuilder {
       macOS: macOS?.toSyntax(),
     );
     final baseHookConfig = hook_syntax.HookInput.fromJson(builder.json).config;
-    baseHookConfig.extensions ??= {};
+    baseHookConfig.extensions ??= hook_syntax.JsonObject.fromJson({});
     final hookConfig = syntax.Config.fromJson(baseHookConfig.json);
     hookConfig.extensions!.codeAssets = codeConfig;
     hookConfig.code = codeConfig; // old location