Impement Proxy object [[isExtensible]] internal method (#3599)

The algorithm is based on ECMA-262 v6, 9.5.3

JerryScript-DCO-1.0-Signed-off-by: Adam Szilagyi aszilagy@inf.u-szeged.hu

tests/jerry/es2015/proxy_is_extensible.js

@@ -12,8 +12,11 @@
 // See the License for the specific language governing permissions and
 // limitations under the License.
 
-// TODO: Update these tests when the internal routine has been implemented
+// Copyright 2015 the V8 project authors. All rights reserved.
+// Use of this source code is governed by a BSD-style license that can be
+// found in the LICENSE file.
 
+// error checks
 var target = {};
 var handler = { isExtensible (target) {
   throw 42;
@@ -26,7 +29,7 @@ try {
   Object.isFrozen(proxy)
   assert(false);
 } catch (e) {
-  assert(e instanceof TypeError);
+  assert(e === 42);
 }
 
 try {
@@ -34,13 +37,128 @@ try {
   Object.isSealed(proxy)
   assert(false);
 } catch (e) {
-  assert(e instanceof TypeError);
+  assert(e === 42);
 }
 
 try {
   // 7.2.5
   Object.isExtensible(proxy)
   assert(false);
+} catch (e) {
+  assert(e === 42);
+}
+
+// no trap
+var target = {};
+var handler = {};
+var proxy = new Proxy(target, handler);
+assert(Object.isExtensible(target) === true)
+assert(Object.isExtensible(proxy) === true);
+Object.preventExtensions(target);
+assert(Object.isExtensible(target) === false);
+assert(Object.isExtensible(proxy) === false);
+
+// undefined trap
+var target = {};
+var handler =  { isExtensible: null };
+var proxy = new Proxy(target, handler);
+assert(Object.isExtensible(target) === true)
+assert(Object.isExtensible(proxy) === true);
+Object.preventExtensions(target);
+assert(Object.isExtensible(target) === false);
+assert(Object.isExtensible(proxy) === false);
+
+// invalid trap
+var target = {};
+var handler =  { isExtensible: true };
+var proxy = new Proxy(target, handler);
+
+try {
+  Object.isExtensible(proxy);
+  assert(false);
+} catch (e) {
+  assert(e instanceof TypeError); 
+}
+
+// valid trap
+var target = { prop1: true };
+var handler = {
+  isExtensible(target) {
+    target.prop1 = false;
+    return Object.isExtensible(target);
+  }
+};
+
+var proxy = new Proxy(target, handler);
+assert(Object.isExtensible(proxy) === true);
+assert(target.prop1 === false);
+Object.preventExtensions(target);
+assert(Object.isExtensible(target) === false);
+assert(Object.isExtensible(proxy) === false);
+
+// trap result is invalid
+var target = {};
+var handler = {
+  isExtensible(target) {
+    return false;
+  }
+};
+
+var proxy = new Proxy(target, handler);
+
+try {
+  Object.isExtensible(proxy);
+  assert(false);
 } catch (e) {
   assert(e instanceof TypeError);
 }
+
+// handler is null
+var target = {};
+var handler = { 
+  isExtensible (target) {
+    return Object.isExtensible(target);
+  }
+};
+
+var revocable = Proxy.revocable (target, {});
+var proxy = revocable.proxy;
+revocable.revoke();
+
+try {
+  Object.isExtensible(proxy);
+  assert(false);
+} catch (e) {
+  assert(e instanceof TypeError);
+}
+
+// proxy within proxy
+var target = {};
+var handler1 = {
+  isExtensible(target) {
+    return Object.isExtensible(target);
+  }
+};
+
+var handler2 = {
+  isExtensible(target) {
+    return false;
+  }
+};
+
+var proxy = new Proxy(target, handler1);
+var proxy2 = new Proxy(proxy, handler1);
+assert(Object.isExtensible(proxy2) === true);
+
+var proxy3 = new Proxy(proxy, handler2);
+
+try {
+  Object.isExtensible(proxy3);
+  assert(false);
+} catch (e) {
+  assert(e instanceof TypeError);
+}
+
+var proxy4 = new Proxy(proxy2, handler1);
+Object.preventExtensions(target);
+assert(Object.isExtensible(proxy4) === false);