[proxies] Wire up Object.getOwnPropertyDescriptor

test/mjsunit/harmony/proxy/proxy-getOwnPropertyDescriptor.js

+// 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.
+
+// Flags: --harmony-proxies
+
+var target = {};
+var configurable_desc = {
+  value: 123,
+  configurable: true,
+  writable: true,
+  enumerable: false,
+};
+Object.defineProperty(target, "configurable", configurable_desc);
+var nonconfigurable_desc = {
+  value: 234,
+  configurable: false,
+  writable: false,
+  enumerable: true
+}
+Object.defineProperty(target, "nonconfigurable", nonconfigurable_desc);

[Camillo Bruni, 2015/11/16 16:15:40]

I'd repeat this exact test with an empty proxy: new Proxy(target, {}), same
above

[Jakob Kummerow, 2015/11/17 12:42:51]

This isn't a test... I guess you mean lines 44/46. Done.

+
+var proxied_desc = {
+  value: 345,
+  configurable: true
+};
+
+var handler = {
+  "getOwnPropertyDescriptor": function(target, name) {
+    if (name === "proxied") {
+      return proxied_desc;
+    }
+    if (name === "return_null") {
+      return null;
+    }
+    return Object.getOwnPropertyDescriptor(target, name);
+  }
+};
+
+var proxy = new Proxy(target, handler);
+
+// Checking basic functionality:

[Camillo Bruni, 2015/11/16 16:15:40]

Maybe this is too much work... I tried to order the test according to the checks
in the spec, makes it a bit easier to find missing cases.

Missing cases (probably should check test262): 
- trap is not a callable (ES6 7.3.9)
- trapResult == undefined

[Jakob Kummerow, 2015/11/17 12:42:51]

Done, added a third section that specifically triggers each bailout.
Testcase added.
See lines 56ff, 69ff.

+
+assertEquals(configurable_desc,
+             Object.getOwnPropertyDescriptor(proxy, "configurable"));
+assertEquals(nonconfigurable_desc,
+             Object.getOwnPropertyDescriptor(proxy, "nonconfigurable"));
+assertEquals({ value: proxied_desc.value,
+               configurable: proxied_desc.configurable,
+               enumerable: false,
+               writable: false },
+             Object.getOwnPropertyDescriptor(proxy, "proxied"));
+
+assertThrows('Object.getOwnPropertyDescriptor(proxy, "return_null")');
+
+handler.getOwnPropertyDescriptor = undefined;
+assertEquals(configurable_desc,
+             Object.getOwnPropertyDescriptor(proxy, "configurable"));
+
+handler.getOwnPropertyDescriptor = function(target, name) {
+  return {value: 456, configurable: true, writable: true}
+};
+assertThrows('Object.getOwnPropertyDescriptor(proxy, "nonconfigurable")');

[Camillo Bruni, 2015/11/16 16:15:40]

please add a comment why this should throw, I end up in
IsCompatiblePropertyDescriptor where we would return true because there is no
property 456 on the target => current = undefined.

[Jakob Kummerow, 2015/11/17 12:42:51]

Done. (It throws because nonconfigurable properties can't be reported as
configurable.)

+
+// Checking invariants mentioned explicitly by the ES spec:
+
+// "A property cannot be reported as non-existent, if it exists as a
+// non-configurable own property of the target object."
+handler.getOwnPropertyDescriptor = function(target, name) { return undefined; };
+assertThrows('Object.getOwnPropertyDescriptor(proxy, "nonconfigurable")');
+assertEquals(undefined, Object.getOwnPropertyDescriptor(proxy, "configurable"));
+
+// "A property cannot be reported as non-configurable, if it does not exist
+// as an own property of the target object or if it exists as a configurable
+// own property of the target object."
+handler.getOwnPropertyDescriptor = function(target, name) {
+  return {value: 234, configurable: false, enumerable: true};
+};
+assertThrows('Object.getOwnPropertyDescriptor(proxy, "nonexistent")');
+assertThrows('Object.getOwnPropertyDescriptor(proxy, "configurable")');
+assertEquals(
+    false,
+    Object.getOwnPropertyDescriptor(proxy, "nonconfigurable").configurable);
+
+// "A property cannot be reported as non-existent, if it exists as an own
+// property of the target object and the target object is not extensible."
+Object.seal(target);
+handler.getOwnPropertyDescriptor = function(target, name) { return undefined; };
+assertThrows('Object.getOwnPropertyDescriptor(proxy, "configurable")');
+assertThrows('Object.getOwnPropertyDescriptor(proxy, "nonconfigurable")');
+assertEquals(undefined, Object.getOwnPropertyDescriptor(proxy, "nonexistent"));
+
+// "A property cannot be reported as existent, if it does not exist as an
+// own property of the target object and the target object is not extensible."
+var existent_desc = {value: "yes"};
+handler.getOwnPropertyDescriptor = function() { return existent_desc; };
+assertThrows('Object.getOwnPropertyDescriptor(proxy, "nonexistent")');
+assertEquals(
+    {value: "yes", writable: false, enumerable: false, configurable: false},
+    Object.getOwnPropertyDescriptor(proxy, "configurable"));