Impelement Proxy object [[preventExtensions]] internal method (#3620)

The algorithm is based on ECMA-262 v6, 9.5.4

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

jerry-core/ecma/operations/ecma-proxy-object.c

@@ -416,8 +416,74 @@ ecma_value_t
 ecma_proxy_object_prevent_extensions (ecma_object_t *obj_p) /**< proxy object */
 {
   JERRY_ASSERT (ECMA_OBJECT_IS_PROXY (obj_p));
-  JERRY_UNUSED (obj_p);
+
-  return ecma_raise_type_error (ECMA_ERR_MSG ("UNIMPLEMENTED: Proxy.[[PreventExtensions]]"));
+  ecma_proxy_object_t *proxy_obj_p = (ecma_proxy_object_t *) obj_p;
+
+  /* 1. */
+  ecma_value_t handler = proxy_obj_p->handler;
+
+  /* 2-5. */
+  ecma_value_t trap = ecma_validate_proxy_object (handler, LIT_MAGIC_STRING_PREVENT_EXTENSIONS_UL);
+
+  /* 6. */
+  if (ECMA_IS_VALUE_ERROR (trap))
+  {
+    return trap;
+  }
+
+  ecma_value_t target = proxy_obj_p->target;
+  ecma_object_t *target_obj_p = ecma_get_object_from_value (target);
+
+  /* 7. */
+  if (ecma_is_value_undefined (trap))
+  {
+    ecma_value_t ret_value = ecma_builtin_object_object_prevent_extensions (target_obj_p);
+
+    if (ECMA_IS_VALUE_ERROR (ret_value))
+    {
+      return ret_value;
+    }
+
+    ecma_deref_object (target_obj_p);
+
+    return ECMA_VALUE_TRUE;
+  }
+
+  ecma_object_t *func_obj_p = ecma_get_object_from_value (trap);
+
+  /* 8. */
+  ecma_value_t trap_result = ecma_op_function_call (func_obj_p, handler, &target, 1);
+
+  ecma_deref_object (func_obj_p);
+
+  /* 9. */
+  if (ECMA_IS_VALUE_ERROR (trap_result))
+  {
+    return trap_result;
+  }
+
+  bool boolean_trap_result = ecma_op_to_boolean (trap_result);
+
+  ecma_free_value (trap_result);
+
+  /* 10. */
+  if (boolean_trap_result)
+  {
+    ecma_value_t target_is_ext = ecma_builtin_object_object_is_extensible (target_obj_p);
+
+    if (ECMA_IS_VALUE_ERROR (target_is_ext))
+    {
+      return target_is_ext;
+    }
+
+    if (ecma_is_value_true (target_is_ext))
+    {
+      return ecma_raise_type_error (ECMA_ERR_MSG ("Trap result does not reflect inextensibility of proxy target"));
+    }
+  }
+
+  /* 11. */
+  return ecma_make_boolean_value (boolean_trap_result);
 } /* ecma_proxy_object_prevent_extensions */
 
 /**

tests/jerry/es2015/proxy_prevent_extensions.js

@@ -12,7 +12,9 @@
 // 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.
 
 var target = {};
 var handler = { preventExtensions (target) {
@@ -26,14 +28,120 @@ try {
   Object.freeze(proxy)
   assert(false);
 } catch (e) {
-  assert(e instanceof TypeError);
+  assert(e === 42);
 }
 
 try {
   // 7.3.14
   Object.seal(proxy)
   assert(false);
+} catch (e) {
+  assert(e === 42);
+}
+
+// test with no trap
+var target = {};
+var handler = {};
+var proxy = new Proxy(target, handler);
+
+assert(Object.isExtensible(target) === true);
+assert(Object.isExtensible(proxy) === true);
+Object.preventExtensions(proxy);
+assert(Object.isExtensible(target) === false);
+assert(Object.isExtensible(proxy) === false);
+
+// test with "undefined" trap
+var target = {};
+var handler = { preventExtensions: null };
+var proxy = new Proxy(target, handler);
+
+assert(Object.isExtensible(target) === true);
+assert(Object.isExtensible(proxy) === true);
+Object.preventExtensions(proxy);
+assert(Object.isExtensible(target) === false);
+assert(Object.isExtensible(proxy) === false);
+
+// test with invalid trap
+var target = {};
+var handler = { preventExtensions: 42 };
+var proxy = new Proxy(target, handler);
+
+try {
+  Object.preventExtensions(proxy);
+  assert(false);
 } catch (e) {
   assert(e instanceof TypeError);
 }
 
+// test with valid trap
+var target = { foo: "bar" };
+var handler = {
+  preventExtensions(target) {
+    target.foo = "foo"
+    Object.preventExtensions(target);
+    return true;
+  }
+}
+
+var proxy = new Proxy(target, handler);
+assert(Object.isExtensible(target) === true);
+assert(Object.isExtensible(proxy) === true);
+assert(target.foo === "bar");
+Object.preventExtensions(proxy);
+assert(Object.isExtensible(target) === false);
+assert(Object.isExtensible(proxy) === false);
+assert(target.foo === "foo");
+
+// test when invariants gets violated
+var target = {};
+var handler = {
+  preventExtensions(target) {
+    return true;
+  }
+}
+
+var proxy = new Proxy(target, handler);
+
+try {
+  Object.preventExtensions(proxy);
+  assert(false);
+} catch (e) {
+  assert(e instanceof TypeError);
+}
+
+// test when target is proxy
+var target = {};
+var handler = {
+  preventExtensions(target) {
+    Object.preventExtensions(target);
+    return true;
+  }
+}
+
+var proxy1 = new Proxy(target, handler);
+var proxy2 = new Proxy(proxy1, handler);
+
+assert(Object.isExtensible(target) === true);
+assert(Object.isExtensible(proxy1) === true);
+assert(Object.isExtensible(proxy2) === true);
+Object.preventExtensions(proxy2);
+assert(Object.isExtensible(target) === false);
+assert(Object.isExtensible(proxy1) === false);
+assert(Object.isExtensible(proxy2) === false);
+
+var target = {};
+var handler = {
+  preventExtensions(target) {
+    return true;
+  }
+}
+
+var proxy1 = new Proxy(target, handler);
+var proxy2 = new Proxy(proxy1, handler);
+
+try {
+  Object.preventExtensions(proxy2);
+  assert(false);
+} catch (e) {
+  assert(e instanceof TypeError);
+}