[jnigen] Make Visitor constructable inline

pkgs/jni/tool/generate_jni_bindings.dart

@@ -21,36 +21,25 @@ const Map<String, String> _constructorAllowList = {
   'Short': 's',
 };
 
-class Renamer extends Visitor {
-  late ClassDecl _class;
-
-  @override
-  void visitClass(ClassDecl c) {
-    _class = c;
-    c.name = 'J${c.originalName}';
-  }
-
-  @override
-  void visitMethod(Method m) {
-    if (!m.isConstructor) return;
-    final sig = _constructorAllowList[_class.originalName];
-    if (sig == null) return;
-    final lister = ListParams();
-    m.accept(lister);
-    m.isExcluded = !(lister.params.length == 1 && lister.params.first == sig);
-  }
-}
-
-class ListParams extends Visitor {
-  List<String> params = [];
-
-  @override
-  void visitParam(Param p) {
-    params.add(p.originalName);
-  }
-}
-
 Future<void> main() async {
+  ClassDecl? currentClass;
+  final renamerVisitor = Visitor.callback(
+    visitClass: (c) {
+      currentClass = c;
+      c.name = 'J${c.originalName}';
+    },
+    visitMethod: (m) {
+      if (!m.isConstructor) return;
+      final sig = _constructorAllowList[currentClass?.originalName];
+      if (sig == null) return;
+      final params = <String>[];
+      m.accept(Visitor.callback(
+        visitParam: (p) => params.add(p.originalName),
+      ));
+      m.isExcluded = !(params.length == 1 && params.first == sig);
+    },
+  );
+
   final classes = [
     'java.lang.Boolean',
     'java.lang.Byte',
@@ -95,7 +84,7 @@ Future<void> main() async {
       hide: classes,
       preamble: preamble,
       generateStubs: false,
-      visitors: [Renamer()],
+      visitors: [renamerVisitor],
     ),
   );
 }

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

@@ -15,6 +15,15 @@ abstract class _Element {
 /// Users can extend this class to create custom visitors that modify the AST
 /// before code generation.
 abstract class Visitor {
+  const Visitor();
+
+  factory Visitor.callback({
+    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 +37,43 @@ abstract class Visitor {
   void visitParam(Param parameter) {}
 }
 
+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;
+
+  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

@@ -29,64 +29,6 @@ extension on Iterable<ast.Field> {
   List<String> get finalNames => map((f) => f.finalName).toList();
 }
 
-// This is customizable by the user
-class UserExcluder extends Visitor {
-  @override
-  void visitClass(ClassDecl c) {
-    if (c.binaryName.contains('y')) {
-      c.isExcluded = true;
-    }
-  }
-
-  @override
-  void visitMethod(Method method) {
-    if (method.name == 'Bar') {
-      method.isExcluded = true;
-    }
-  }
-
-  @override
-  void visitField(Field field) {
-    if (field.name == 'Bar') {
-      field.isExcluded = true;
-    }
-  }
-}
-
-// 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');
-    }
-  }
-
-  @override
-  void visitParam(Param parameter) {
-    if (parameter.originalName.contains('Foo')) {
-      parameter.name = parameter.originalName.replaceAll('Foo', 'Bar');
-    }
-  }
-}
-
 Future<void> rename(ast.Classes classes) async {
   final config = Config(
       outputConfig: OutputConfig(
@@ -135,7 +77,25 @@ void main() {
     });
 
     final simpleClasses = Classes(classes);
-    simpleClasses.accept(UserExcluder());
+    simpleClasses.accept(
+      Visitor.callback(
+        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 +141,33 @@ void main() {
     });
 
     final simpleClasses = Classes(classes);
-    simpleClasses.accept(UserRenamer());
+    simpleClasses.accept(
+      Visitor.callback(
+        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);