[jnigen] Make Visitor constructable inline

pkgs/jni/tool/generate_jni_bindings.dart

@@ -21,32 +21,27 @@ const Map<String, String> _constructorAllowList = {
   'Short': 's',
 };
 
-class Renamer extends Visitor {
-  late ClassDecl _class;
+base class Renamer extends Visitor {
+  Renamer() : super.base();
+
+  ClassDecl? _currentClass;
 
   @override
   void visitClass(ClassDecl c) {
-    _class = c;
+    _currentClass = c;
     c.name = 'J${c.originalName}';
   }
 
   @override
   void visitMethod(Method m) {
     if (!m.isConstructor) return;
-    final sig = _constructorAllowList[_class.originalName];
+    final sig = _constructorAllowList[_currentClass?.originalName];
     if (sig == null) return;
-    final lister = ListParams();
-    m.accept(lister);
-    m.isExcluded = !(lister.params.length == 1 && lister.params.first == sig);
-  }
-}
-
-class ListParams extends Visitor {
-  List<String> params = [];
-
-  @override
-  void visitParam(Param p) {
-    params.add(p.originalName);
+    final params = <String>[];
+    m.accept(Visitor(
+      visitParam: (p) => params.add(p.originalName),
+    ));
+    m.isExcluded = !(params.length == 1 && params.first == sig);
   }
 }
 

pkgs/jnigen/example/maven_libs/example/lib/main.dart

@@ -39,7 +39,8 @@ class _MyAppState extends State<MyApp> {
       final json = gson.toJson(map.as(JObject.type))!.toDartString();
 
       setState(() {
-        _status = '''
+        _status =
+            '''
 JSON from Gson: $json
 OkHttpClient: ${client.toString()}''';
       });

pkgs/jnigen/example/maven_libs_groovy/example/lib/main.dart

@@ -39,7 +39,8 @@ class _MyAppState extends State<MyApp> {
       final json = gson.toJson(map.as(JObject.type))!.toDartString();
 
       setState(() {
-        _status = '''
+        _status =
+            '''
 JSON from Gson: $json
 OkHttpClient: ${client.toString()}''';
       });

pkgs/jnigen/lib/src/elements/j_elements.dart

@@ -14,7 +14,16 @@ abstract class _Element {
 ///
 /// Users can extend this class to create custom visitors that modify the AST
 /// before code generation.
-abstract class Visitor {
+abstract base class Visitor {
+  const Visitor.base();
+
+  factory Visitor({
+    void Function(ClassDecl node)? visitClass,
+    void Function(Method node)? visitMethod,
+    void Function(Field node)? visitField,
+    void Function(Param node)? visitParam,
+  }) = _VisitorImpl;
+
   /// Visits a class declaration.
   void visitClass(ClassDecl c) {}
 
@@ -28,6 +37,44 @@ abstract class Visitor {
   void visitParam(Param parameter) {}
 }
 
+final class _VisitorImpl extends Visitor {
+  const _VisitorImpl({
+    void Function(ClassDecl node)? visitClass,
+    void Function(Method node)? visitMethod,
+    void Function(Field node)? visitField,
+    void Function(Param node)? visitParam,
+  })  : _visitClass = visitClass,
+        _visitMethod = visitMethod,
+        _visitField = visitField,
+        _visitParam = visitParam,
+        super.base();
+
+  final void Function(ClassDecl node)? _visitClass;
+  final void Function(Method node)? _visitMethod;
+  final void Function(Field node)? _visitField;
+  final void Function(Param node)? _visitParam;
+
+  @override
+  void visitClass(ClassDecl c) {
+    _visitClass?.call(c);
+  }
+
+  @override
+  void visitMethod(Method method) {
+    _visitMethod?.call(method);
+  }
+
+  @override
+  void visitField(Field field) {
+    _visitField?.call(field);
+  }
+
+  @override
+  void visitParam(Param parameter) {
+    _visitParam?.call(parameter);
+  }
+}
+
 /// A collection of class declarations.
 class Classes implements _Element {
   Classes(this._classes);

pkgs/jnigen/test/user_visitor_test.dart

@@ -29,8 +29,22 @@ extension on Iterable<ast.Field> {
   List<String> get finalNames => map((f) => f.finalName).toList();
 }
 
-// This is customizable by the user
-class UserExcluder extends Visitor {
+Future<void> rename(ast.Classes classes) async {
+  final config = Config(
+      outputConfig: OutputConfig(
+        dartConfig: DartCodeOutputConfig(
+          path: Uri.file('test.dart'),
+          structure: OutputStructure.singleFile,
+        ),
+      ),
+      classes: []);
+  await classes.accept(Linker(config));
+  classes.accept(Renamer(config));
+}
+
+base class CustomVisitor extends Visitor {
+  CustomVisitor() : super.base();
+
   @override
   void visitClass(ClassDecl c) {
     if (c.binaryName.contains('y')) {
@@ -53,54 +67,51 @@ class UserExcluder extends Visitor {
   }
 }
 
-// This is customizable by the user
-class UserRenamer extends Visitor {
-  @override
-  void visitClass(ClassDecl c) {
-    if (c.originalName.contains('Foo')) {
-      c.name = c.originalName.replaceAll('Foo', 'Bar');
-    }
-  }
-
-  @override
-  void visitMethod(Method method) {
-    if (method.originalName.contains('Foo')) {
-      method.name = method.originalName.replaceAll('Foo', 'Bar');
-    }
-    if (method.isConstructor) {
-      method.name = 'constructor';
-    }
-  }
-
-  @override
-  void visitField(Field field) {
-    if (field.originalName.contains('Foo')) {
-      field.name = field.originalName.replaceAll('Foo', 'Bar');
-    }
-  }
+void main() {
+  test('Exclude something using custom Visitor subclass', () async {
+    final classes = ast.Classes({
+      'Foo': ast.ClassDecl(
+        binaryName: 'Foo',
+        declKind: ast.DeclKind.classKind,
+        superclass: ast.DeclaredType.object,
+        methods: [
+          ast.Method(name: 'foo', returnType: ast.DeclaredType.object),
+          ast.Method(name: 'Bar', returnType: ast.DeclaredType.object),
+          ast.Method(name: 'foo1', returnType: ast.DeclaredType.object),
+          ast.Method(name: 'Bar', returnType: ast.DeclaredType.object),
+        ],
+        fields: [
+          ast.Field(name: 'foo', type: ast.DeclaredType.object),
+          ast.Field(name: 'Bar', type: ast.DeclaredType.object),
+          ast.Field(name: 'foo1', type: ast.DeclaredType.object),
+          ast.Field(name: 'Bar', type: ast.DeclaredType.object),
+        ],
+      ),
+      'y.Foo': ast.ClassDecl(
+          binaryName: 'y.Foo',
+          declKind: ast.DeclKind.classKind,
+          superclass: ast.DeclaredType.object,
+          methods: [
+            ast.Method(name: 'foo', returnType: ast.DeclaredType.object),
+            ast.Method(name: 'Bar', returnType: ast.DeclaredType.object),
+          ],
+          fields: [
+            ast.Field(name: 'foo', type: ast.DeclaredType.object),
+            ast.Field(name: 'Bar', type: ast.DeclaredType.object),
+          ]),
+    });
 
-  @override
-  void visitParam(Param parameter) {
-    if (parameter.originalName.contains('Foo')) {
-      parameter.name = parameter.originalName.replaceAll('Foo', 'Bar');
-    }
-  }
-}
+    final simpleClasses = Classes(classes);
+    simpleClasses.accept(CustomVisitor());
 
-Future<void> rename(ast.Classes classes) async {
-  final config = Config(
-      outputConfig: OutputConfig(
-        dartConfig: DartCodeOutputConfig(
-          path: Uri.file('test.dart'),
-          structure: OutputStructure.singleFile,
-        ),
-      ),
-      classes: []);
-  await classes.accept(Linker(config));
-  classes.accept(Renamer(config));
-}
+    expect(classes.decls['y.Foo']?.isExcluded, true);
+    expect(classes.decls['Foo']?.isExcluded, false);
 
-void main() {
+    expect(classes.decls['Foo']?.fields.isExcludedValues,
+        [false, true, false, true]);
+    expect(classes.decls['Foo']?.methods.isExcludedValues,
+        [false, true, false, true]);
+  });
   test('Exclude something using the user excluder, Simple AST', () async {
     final classes = ast.Classes({
       'Foo': ast.ClassDecl(
@@ -135,7 +146,25 @@ void main() {
     });
 
     final simpleClasses = Classes(classes);
-    simpleClasses.accept(UserExcluder());
+    simpleClasses.accept(
+      Visitor(
+        visitClass: (c) {
+          if (c.binaryName.contains('y')) {
+            c.isExcluded = true;
+          }
+        },
+        visitMethod: (method) {
+          if (method.name == 'Bar') {
+            method.isExcluded = true;
+          }
+        },
+        visitField: (field) {
+          if (field.name == 'Bar') {
+            field.isExcluded = true;
+          }
+        },
+      ),
+    );
 
     expect(classes.decls['y.Foo']?.isExcluded, true);
     expect(classes.decls['Foo']?.isExcluded, false);
@@ -181,7 +210,33 @@ void main() {
     });
 
     final simpleClasses = Classes(classes);
-    simpleClasses.accept(UserRenamer());
+    simpleClasses.accept(
+      Visitor(
+        visitClass: (c) {
+          if (c.originalName.contains('Foo')) {
+            c.name = c.originalName.replaceAll('Foo', 'Bar');
+          }
+        },
+        visitMethod: (method) {
+          if (method.originalName.contains('Foo')) {
+            method.name = method.originalName.replaceAll('Foo', 'Bar');
+          }
+          if (method.isConstructor) {
+            method.name = 'constructor';
+          }
+        },
+        visitField: (field) {
+          if (field.originalName.contains('Foo')) {
+            field.name = field.originalName.replaceAll('Foo', 'Bar');
+          }
+        },
+        visitParam: (parameter) {
+          if (parameter.originalName.contains('Foo')) {
+            parameter.name = parameter.originalName.replaceAll('Foo', 'Bar');
+          }
+        },
+      ),
+    );
 
     await rename(classes);