[package:js] Add test for inheritance between classes

Adds a test to verify that JS interop and anonymous classes can
properly extend one another and that member access behaves as
expected.

Change-Id: I98b77444363ec3f985a9a10f3716e15a7fd970f5
Reviewed-on: https://dart-review.googlesource.com/c/sdk/+/164882
Reviewed-by: Sigmund Cherem <[email protected]>

Author: srujzs

tests/lib/js/extends_test/extends_test.dart

@@ -0,0 +1,57 @@
+// Copyright (c) 2020, the Dart project authors.  Please see the AUTHORS file
+// for details. All rights reserved. Use of this source code is governed by a
+// BSD-style license that can be found in the LICENSE file.
+
+import 'extends_test_util.dart';
+
+void main() {
+  // Use the old way to define inheritance between JS objects.
+  eval(r"""
+    function inherits(child, parent) {
+      if (child.prototype.__proto__) {
+        child.prototype.__proto__ = parent.prototype;
+      } else {
+        function tmp() {};
+        tmp.prototype = parent.prototype;
+        child.prototype = new tmp();
+        child.prototype.constructor = child;
+      }
+    }
+    function JSClass(a) {
+      this.a = a;
+      this.getA = function() {
+        return this.a;
+      }
+      this.getAOrB = function() {
+        return this.getA();
+      }
+    }
+    function JSExtendJSClass(a, b) {
+      JSClass.call(this, a);
+      this.b = b;
+      this.getB = function() {
+        return this.b;
+      }
+      this.getAOrB = function() {
+        return this.getB();
+      }
+    }
+    inherits(JSExtendJSClass, JSClass);
+    function JSExtendAnonymousClass(a, b) {
+      this.a = a;
+      this.b = b;
+      this.getA = function() {
+        return this.a;
+      }
+      this.getB = function() {
+        return this.b;
+      }
+      this.getAOrB = function() {
+        return this.getB();
+      }
+    }
+    self.anonExtendAnon = new JSExtendAnonymousClass(1, 2);
+    self.anonExtendJS = new JSExtendJSClass(1, 2);
+  """);
+  testInheritance();
+}

tests/lib/js/extends_test/extends_test_util.dart

@@ -0,0 +1,94 @@
+// Copyright (c) 2020, the Dart project authors.  Please see the AUTHORS file
+// for details. All rights reserved. Use of this source code is governed by a
+// BSD-style license that can be found in the LICENSE file.
+
+// Tests inheritance relationships between `JS` and `anonymous` classes/objects.
+
+@JS()
+library extends_test;
+
+import 'package:expect/minitest.dart';
+import 'package:js/js.dart';
+
+@JS()
+external void eval(String code);
+
+@JS()
+class JSClass {
+  external int get a;
+  external int getA();
+  external int getAOrB();
+}
+
+@JS()
+@anonymous
+class AnonymousClass {
+  external int get a;
+  external int getA();
+}
+
+@JS()
+class JSExtendJSClass extends JSClass {
+  external JSExtendJSClass(int a, int b);
+  external int get b;
+  external int getB();
+  external int getAOrB();
+}
+
+@JS()
+class JSExtendAnonymousClass extends AnonymousClass {
+  external JSExtendAnonymousClass(int a, int b);
+  external int get b;
+  external int getB();
+}
+
+@JS()
+@anonymous
+class AnonymousExtendAnonymousClass extends AnonymousClass {
+  external int get b;
+  external int getB();
+}
+
+@JS()
+@anonymous
+class AnonymousExtendJSClass extends JSClass {
+  external int get b;
+  external int getB();
+  external int getAOrB();
+}
+
+external AnonymousExtendAnonymousClass get anonExtendAnon;
+external AnonymousExtendJSClass get anonExtendJS;
+
+void testInheritance() {
+  // Note that for the following, there are no meaningful tests for is checks or
+  // as casts, since the web compilers should return true and succeed for all JS
+  // types.
+
+  var jsExtendJS = JSExtendJSClass(1, 2);
+  expect(jsExtendJS.a, 1);
+  expect(jsExtendJS.b, 2);
+  expect(jsExtendJS.getA(), 1);
+  expect(jsExtendJS.getB(), 2);
+  // Test method overrides.
+  expect(jsExtendJS.getAOrB(), 2);
+  expect((jsExtendJS as JSClass).getAOrB(), 2);
+
+  var jsExtendAnon = JSExtendAnonymousClass(1, 2);
+  expect(jsExtendAnon.a, 1);
+  expect(jsExtendAnon.b, 2);
+  expect(jsExtendAnon.getA(), 1);
+  expect(jsExtendAnon.getB(), 2);
+
+  expect(anonExtendAnon.a, 1);
+  expect(anonExtendAnon.b, 2);
+  expect(anonExtendAnon.getA(), 1);
+  expect(anonExtendAnon.getB(), 2);
+
+  expect(anonExtendJS.a, 1);
+  expect(anonExtendJS.b, 2);
+  expect(anonExtendJS.getA(), 1);
+  expect(anonExtendJS.getB(), 2);
+  expect(anonExtendJS.getAOrB(), 2);
+  expect((anonExtendJS as JSClass).getAOrB(), 2);
+}

tests/lib/js/extends_test/extends_with_es6_test.dart

@@ -0,0 +1,54 @@
+// Copyright (c) 2020, the Dart project authors.  Please see the AUTHORS file
+// for details. All rights reserved. Use of this source code is governed by a
+// BSD-style license that can be found in the LICENSE file.
+
+import 'extends_test_util.dart';
+
+void main() {
+  // Use the ES6 syntax for classes to make inheritance easier.
+  eval(r"""
+    class JSClass {
+      constructor(a) {
+        this.a = a;
+      }
+      getA() {
+        return this.a;
+      }
+      getAOrB() {
+        return this.getA();
+      }
+    }
+    class JSExtendJSClass extends JSClass {
+      constructor(a, b) {
+        super(a);
+        this.b = b;
+      }
+      getB() {
+        return this.b;
+      }
+      getAOrB() {
+        return this.getB();
+      }
+    }
+    self.JSExtendJSClass = JSExtendJSClass;
+    class JSExtendAnonymousClass {
+      constructor(a, b) {
+        this.a = a;
+        this.b = b;
+      }
+      getA() {
+        return this.a;
+      }
+      getB() {
+        return this.b;
+      }
+      getAOrB() {
+        return this.getB();
+      }
+    }
+    self.JSExtendAnonymousClass = JSExtendAnonymousClass;
+    self.anonExtendAnon = new JSExtendAnonymousClass(1, 2);
+    self.anonExtendJS = new JSExtendJSClass(1, 2);
+  """);
+  testInheritance();
+}