[ffigen] Support default constructor (#2030)

Author: liamappelbe

pkgs/ffigen/CHANGELOG.md

@@ -2,6 +2,8 @@
 
 - Add variable substitutions that can be used in the `headers.entry-points` to
   locate Apple APIs: `$XCODE`, `$IOS_SDK`, and `$MACOS_SDK`.
+- Add an empty constructor to all ObjC interfaces that have a `new` method,
+  which just calls that method.
 - __Breaking change__: Change the `usrTypeMappings` field of `Config`'s factory
   constructor from a `List<ImportedType>` to a `Map<String, ImportedType>`.
 - Add a `keepIsolateAlive` parameter to the block and protocol constructors that

pkgs/ffigen/lib/src/code_generator/objc_interface.dart

@@ -127,6 +127,20 @@ ${generateAsStub ? '' : _generateMethods(w)}
 ''');
     s.write(generateMethodBindings(w, this));
 
+    final newMethod = methods
+        .where((ObjCMethod m) =>
+            m.isClassMethod &&
+            m.family == ObjCMethodFamily.new_ &&
+            m.params.isEmpty &&
+            m.originalName == 'new')
+        .firstOrNull;
+    if (newMethod != null && originalName != 'NSString') {
+      s.write('''
+  /// Returns a new instance of $name constructed with the default `new` method.
+  factory $name() => ${newMethod.dartMethodName}();
+''');
+    }
+
     return s.toString();
   }
 

pkgs/ffigen/lib/src/code_generator/objc_methods.dart

@@ -194,6 +194,7 @@ class ObjCMethod extends AstNode {
   final String? dartDoc;
   final String originalName;
   final String name;
+  String? dartMethodName;
   final ObjCProperty? property;
   Type returnType;
   final List<Parameter> params;
@@ -338,7 +339,8 @@ class ObjCMethod extends AstNode {
 
   String generateBindings(
       Writer w, ObjCInterface target, UniqueNamer methodNamer) {
-    final methodName = getDartMethodName(methodNamer);
+    dartMethodName ??= getDartMethodName(methodNamer);
+    final methodName = dartMethodName!;
     final upperName = methodName[0].toUpperCase() + methodName.substring(1);
     final s = StringBuffer();
 

pkgs/ffigen/test/native_objc_test/arc_test.dart

@@ -38,7 +38,7 @@ void main() {
 
     (Pointer<ObjCObject>, Pointer<ObjCObject>) newMethodsInner(
         Pointer<Int32> counter) {
-      final obj1 = ArcTestObject.new1();
+      final obj1 = ArcTestObject();
       obj1.setCounter_(counter);
       expect(counter.value, 1);
       final obj2 = ArcTestObject.newWithCounter_(counter);

pkgs/ffigen/test/native_objc_test/bad_method_test.dart

@@ -25,14 +25,14 @@ void main() {
     });
 
     test("Test incomplete struct methods that weren't skipped", () {
-      final obj = BadMethodTestObject.new1();
+      final obj = BadMethodTestObject();
       final structPtr = obj.incompletePointerReturn();
       expect(structPtr.address, 1234);
       expect(obj.incompletePointerParam_(structPtr), 1234);
     });
 
     test("Test bit field methods that weren't skipped", () {
-      final obj = BadMethodTestObject.new1();
+      final obj = BadMethodTestObject();
       final bitFieldPtr = obj.bitFieldPointerReturn();
       expect(bitFieldPtr.address, 5678);
       expect(obj.bitFieldPointerParam_(bitFieldPtr), 5678);

pkgs/ffigen/test/native_objc_test/bad_override_test.dart

@@ -31,48 +31,48 @@ void main() {
       // method in some classes of the heirarchy, and a property in others. This
       // isn't allowed in Dart, so we change all such conflicts to properties.
       // https://github.com/dart-lang/native/issues/1220
-      expect(BadOverrideParent.new1().methodVsGetter, 1);
-      expect(BadOverrideChild.new1().methodVsGetter, 11);
-      expect(BadOverrideSibbling.new1().methodVsGetter, 12);
-      expect(BadOverrideGrandchild.new1().methodVsGetter, 111);
+      expect(BadOverrideParent().methodVsGetter, 1);
+      expect(BadOverrideChild().methodVsGetter, 11);
+      expect(BadOverrideSibbling().methodVsGetter, 12);
+      expect(BadOverrideGrandchild().methodVsGetter, 111);
 
-      var inst = BadOverrideParent.new1();
+      var inst = BadOverrideParent();
       expect(inst.methodVsGetter, 1);
-      inst = BadOverrideChild.new1();
+      inst = BadOverrideChild();
       expect(inst.methodVsGetter, 11);
-      inst = BadOverrideSibbling.new1();
+      inst = BadOverrideSibbling();
       expect(inst.methodVsGetter, 12);
-      inst = BadOverrideGrandchild.new1();
+      inst = BadOverrideGrandchild();
       expect(inst.methodVsGetter, 111);
 
       // Uncle isn't affected by the transform, so has an ordinary method.
-      expect(BadOverrideUncle.new1().methodVsGetter(), 2);
+      expect(BadOverrideUncle().methodVsGetter(), 2);
     });
 
     test('Contravariant returns', () {
       // Return types are supposed to be covariant, but ObjC allows them to be
       // contravariant.
       // https://github.com/dart-lang/native/issues/1220
-      Polygon parentResult = BadOverrideParent.new1().contravariantReturn();
+      Polygon parentResult = BadOverrideParent().contravariantReturn();
       expect(parentResult.name().toDartString(), 'Rectangle');
 
-      Polygon childResult = BadOverrideChild.new1().contravariantReturn();
+      Polygon childResult = BadOverrideChild().contravariantReturn();
       expect(childResult.name().toDartString(), 'Triangle');
     });
 
     test('Covariant args', () {
       // Arg types are supposed to be contravariant, but ObjC allows them to be
       // covariant.
       // https://github.com/dart-lang/native/issues/1220
-      final square = Square.new1();
-      final triangle = Triangle.new1();
+      final square = Square();
+      final triangle = Triangle();
 
-      var parent = BadOverrideParent.new1();
+      var parent = BadOverrideParent();
       expect(parent.covariantArg_(square).toDartString(), 'Polygon: Square');
       expect(
           parent.covariantArg_(triangle).toDartString(), 'Polygon: Triangle');
 
-      parent = BadOverrideChild.new1();
+      parent = BadOverrideChild();
       expect(parent.covariantArg_(square).toDartString(), 'Rectangle: Square');
       expect(() => parent.covariantArg_(triangle), throwsA(isA<TypeError>()));
     });

pkgs/ffigen/test/native_objc_test/block_inherit_test.dart

@@ -31,18 +31,18 @@ void main() {
     });
 
     test('BlockInheritTestBase', () {
-      final BlockInheritTestBase baseObj = BlockInheritTestBase.new1();
+      final BlockInheritTestBase baseObj = BlockInheritTestBase();
       expect(baseObj.getAnimal().laysEggs(), false);
-      expect(baseObj.acceptAnimal_(Platypus.new1()), true);
+      expect(baseObj.acceptAnimal_(Platypus()), true);
 
       final ObjCBlock<Mammal Function()> returner = baseObj.getReturner();
       final Mammal returnerResult = returner();
       expect(returnerResult.laysEggs(), false);
 
       final ObjCBlock<Bool Function(Platypus)> accepter = baseObj.getAccepter();
-      expect(accepter(Platypus.new1()), true);
+      expect(accepter(Platypus()), true);
 
-      final platypus = Platypus.new1();
+      final platypus = Platypus();
       final ObjCBlock<Platypus Function()> platypusReturner =
           ObjCBlock_Platypus.fromFunction(() => platypus);
       expect(baseObj.invokeReturner_(platypusReturner).laysEggs(), true);
@@ -54,11 +54,11 @@ void main() {
     });
 
     test('BlockInheritTestChild', () {
-      final BlockInheritTestChild childObj = BlockInheritTestChild.new1();
+      final BlockInheritTestChild childObj = BlockInheritTestChild();
       final BlockInheritTestBase baseObj = childObj;
       expect(baseObj.getAnimal().laysEggs(), true);
-      expect(baseObj.acceptAnimal_(Platypus.new1()), true);
-      expect(childObj.acceptAnimal_(Mammal.new1()), false);
+      expect(baseObj.acceptAnimal_(Platypus()), true);
+      expect(childObj.acceptAnimal_(Mammal()), false);
 
       final ObjCBlock<Mammal Function()> baseReturner = baseObj.getReturner();
       final Mammal baseReturnerResult = baseReturner();
@@ -71,19 +71,19 @@ void main() {
 
       final ObjCBlock<Bool Function(Platypus)> baseAccepter =
           baseObj.getAccepter();
-      expect(baseAccepter(Platypus.new1()), true);
+      expect(baseAccepter(Platypus()), true);
 
       final ObjCBlock<Bool Function(Mammal)> childAccepter =
           childObj.getAccepter();
-      expect(childAccepter(Mammal.new1()), false);
-      expect(childAccepter(Platypus.new1()), true);
+      expect(childAccepter(Mammal()), false);
+      expect(childAccepter(Platypus()), true);
 
-      final platypus = Platypus.new1();
+      final platypus = Platypus();
       final ObjCBlock<Platypus Function()> platypusReturner =
           ObjCBlock_Platypus.fromFunction(() => platypus);
       expect(baseObj.invokeReturner_(platypusReturner).laysEggs(), true);
 
-      final mammal = Mammal.new1();
+      final mammal = Mammal();
       final ObjCBlock<Mammal Function()> mammalReturner =
           ObjCBlock_Mammal.fromFunction(() => mammal);
       expect(childObj.invokeReturner_(mammalReturner).laysEggs(), false);

pkgs/ffigen/test/native_objc_test/block_test.dart

@@ -250,7 +250,7 @@ void main() {
         return x;
       });
 
-      final obj = DummyObject.new1();
+      final obj = DummyObject();
       final result1 = block(obj);
       expect(result1, obj);
       expect(isCalled, isTrue);
@@ -269,7 +269,7 @@ void main() {
         return x;
       });
 
-      final obj = DummyObject.new1();
+      final obj = DummyObject();
       final result1 = block(obj);
       expect(result1, obj);
       expect(isCalled, isTrue);
@@ -732,7 +732,7 @@ void main() {
     }, skip: !canDoGC);
 
     test('Blocking block ref counting same thread', () async {
-      DummyObject? dummyObject = DummyObject.new1();
+      DummyObject? dummyObject = DummyObject();
       DartObjectListenerBlock? block =
           ObjectListenerBlock.blocking((DummyObject obj) {
         // Object passed as argument.
@@ -762,7 +762,7 @@ void main() {
 
     test('Blocking block ref counting new thread', () async {
       final completer = Completer<void>();
-      DummyObject? dummyObject = DummyObject.new1();
+      DummyObject? dummyObject = DummyObject();
       DartObjectListenerBlock? block =
           ObjectListenerBlock.blocking((DummyObject obj) {
         // Object passed as argument.
@@ -828,7 +828,7 @@ void main() {
 
     (BlockTester, Pointer<ObjCBlockImpl>, Pointer<ObjCObject>) regress1571Inner(
         Completer<void> completer) {
-      final dummyObject = DummyObject.new1();
+      final dummyObject = DummyObject();
       DartObjectListenerBlock? block =
           ObjectListenerBlock.listener((DummyObject obj) {
         expect(objectRetainCount(obj.ref.pointer), greaterThan(0));

pkgs/ffigen/test/native_objc_test/cast_test.dart

@@ -25,7 +25,7 @@ void main() {
       final dylib = File('test/native_objc_test/objc_test.dylib');
       verifySetupFile(dylib);
       DynamicLibrary.open(dylib.absolute.path);
-      testInstance = Castaway.new1();
+      testInstance = Castaway();
       generateBindingsForCoverage('cast');
     });
 
@@ -57,7 +57,7 @@ void main() {
       final meAsInt = testInstance!.meAsInt();
       final fromCast =
           Castaway.castFromPointer(Pointer<ObjCObject>.fromAddress(meAsInt));
-      expect(fromCast, isNot(equals(NSObject.new1())));
+      expect(fromCast, isNot(equals(NSObject())));
     });
   });
 }

pkgs/ffigen/test/native_objc_test/category_test.dart

@@ -27,7 +27,7 @@ void main() {
     });
 
     test('Category methods', () {
-      final thing = Thing.new1();
+      final thing = Thing();
       expect(thing.add_Y_(1000, 234), 1234);
       expect(thing.sub_Y_(1234, 1000), 234);
       expect(thing.mul_Y_(1234, 1000), 1234000);
@@ -38,13 +38,13 @@ void main() {
     });
 
     test('Protocol methods', () {
-      final thing = Thing.new1();
+      final thing = Thing();
       expect(thing.protoMethod(), 987);
       expect(CatImplementsProto.staticProtoMethod(), 654);
     });
 
     test('Instancetype', () {
-      Thing thing1 = Thing.new1();
+      Thing thing1 = Thing();
       expect(Thing.isInstance(thing1), isTrue);
       expect(ChildOfThing.isInstance(thing1), isFalse);
 
@@ -53,7 +53,7 @@ void main() {
       expect(Thing.isInstance(thing2), isTrue);
       expect(ChildOfThing.isInstance(thing2), isFalse);
 
-      ChildOfThing child1 = ChildOfThing.new1();
+      ChildOfThing child1 = ChildOfThing();
       expect(Thing.isInstance(child1), isTrue);
       expect(ChildOfThing.isInstance(child1), isTrue);