[jnigen] Run object default methods for interfaces

pkgs/jni/CHANGELOG.md

@@ -10,6 +10,8 @@
   them in a for-loop or use methods such as `map` on them.
 
 - Added nullable type classes for all Java objects.
+- Fixed a problem where interfaces implemented in Dart would crash when calling
+  the default object methods: `equals`, `hashCode`, and `toString`.
 
 ## 0.12.2
 

pkgs/jni/java/src/main/java/com/github/dart_lang/jni/PortProxyBuilder.java

@@ -9,8 +9,20 @@
 
 public class PortProxyBuilder implements InvocationHandler {
   private static final PortCleaner cleaner = new PortCleaner();
+  private static final Method equals;
+  private static final Method hashCode;
+  private static final Method toString;
 
   static {
+    Class<Object> object = Object.class;
+    try {
+      equals = object.getDeclaredMethod("equals", object);
+      hashCode = object.getDeclaredMethod("hashCode");
+      toString = object.getDeclaredMethod("toString");
+    } catch (NoSuchMethodException e) {
+      // Never happens.
+      throw new Error();
+    }
     System.loadLibrary("dartjni");
   }
 
@@ -115,6 +127,15 @@ private static native Object[] _invoke(
 
   @Override
   public Object invoke(Object proxy, Method method, Object[] args) throws Throwable {
+    if (method.equals(equals)) {
+      return proxy == args[0];
+    }
+    if (method.equals(hashCode)) {
+      return System.identityHashCode(proxy);
+    }
+    if (method.equals(toString)) {
+      return proxy.getClass().getName() + '@' + Integer.toHexString(System.identityHashCode(proxy));
+    }
     DartImplementation implementation = implementations.get(method.getDeclaringClass().getName());
     String descriptor = getDescriptor(method);
     boolean isBlocking = !asyncMethods.contains(descriptor);

pkgs/jnigen/test/simple_package_test/runtime_test_registrant.dart

@@ -33,6 +33,15 @@ void _runJavaGC() {
   } while (result.exitCode != 0);
 }
 
+Future<void> _waitUntil(bool Function() predicate) async {
+  for (var i = 0; i < 8; ++i) {
+    await Future<void>.delayed(Duration(milliseconds: (1 << i) * 100));
+    if (predicate()) {
+      return;
+    }
+  }
+}
+
 void registerTests(String groupName, TestRunnerCallback test) {
   group(groupName, () {
     test('static final fields - int', () {
@@ -636,14 +645,7 @@ void registerTests(String groupName, TestRunnerCallback test) {
           // Running garbage collection does not work on Android. Skipping this
           // test for android.
           _runJavaGC();
-          for (var i = 0; i < 8; ++i) {
-            await Future<void>.delayed(Duration(milliseconds: (1 << i) * 100));
-            if (MyInterface.$impls.isEmpty) {
-              break;
-            }
-          }
-          // Since the interface is now deleted, the cleaner must signal to Dart
-          // to clean up.
+          await _waitUntil(() => MyInterface.$impls.isEmpty);
           expect(MyInterface.$impls, isEmpty);
         }
       });
@@ -688,12 +690,7 @@ void registerTests(String groupName, TestRunnerCallback test) {
           // Running garbage collection does not work on Android. Skipping this
           // test for android.
           _runJavaGC();
-          for (var i = 0; i < 8; ++i) {
-            await Future<void>.delayed(Duration(milliseconds: (1 << i) * 100));
-            if (MyInterface.$impls.isEmpty) {
-              break;
-            }
-          }
+          await _waitUntil(() => MyInterface.$impls.isEmpty);
           // Since the interface is now deleted, the cleaner must signal to Dart
           // to clean up.
           expect(MyInterface.$impls, isEmpty);
@@ -741,19 +738,31 @@ void registerTests(String groupName, TestRunnerCallback test) {
             // Running garbage collection does not work on Android. Skipping
             // this test for android.
             _runJavaGC();
-            for (var i = 0; i < 8; ++i) {
-              await Future<void>.delayed(
-                  Duration(milliseconds: (1 << i) * 100));
-              if (MyInterface.$impls.isEmpty) {
-                break;
-              }
-            }
+            await _waitUntil(() => MyInterface.$impls.isEmpty);
             // Since the interface is now deleted, the cleaner must signal to
             // Dart to clean up.
             expect(MyRunnable.$impls, isEmpty);
           }
         });
       }
+      test('Object methods work', () async {
+        final runnable = MyRunnable.implement($MyRunnable(
+          run: () {},
+        ));
+        expect(runnable == runnable, true);
+        expect(runnable != runnable, false);
+        expect(runnable.hashCode, runnable.hashCode);
+        expect(runnable.toString(), runnable.toString());
+        expect(MyRunnable.$impls, hasLength(1));
+        runnable.release();
+        if (!Platform.isAndroid) {
+          // Running garbage collection does not work on Android. Skipping
+          // this test for android.
+          _runJavaGC();
+          await _waitUntil(() => MyInterface.$impls.isEmpty);
+          expect(MyRunnable.$impls, isEmpty);
+        }
+      });
     }
     group('Dart exceptions are handled', () {
       for (final exception in [UnimplementedError(), 'Hello!']) {