1. Open web console 2. Enter this code: var obj = Object.create(null); obj.__proto__ = []; obj; Result: Object { undefined: undefined, undefined: undefined, undefined: undefined } Expected: Object { __proto__: [] } 3. Inspect the object Result: no property Expected: ▶ __proto__ : Array [] BTW, now that you are creating a new console and object inspector, I think it's a good time to remove the confusing magic about __proto__. I would reference the [[Prototype]] using the console's notation for internal slots, i.e. <proto> or <prototype> instead of __proto__. And I would show this on all non-proxy objects, including Object.create(null) and Object.prototype.

Here's the packet we get at the moment: ```json { "type": "object", "actor": "server2.conn2.child1/obj27", "class": "Object", "extensible": true, "frozen": false, "sealed": false, "ownPropertyLength": 1, "preview": { "kind": "Object", "ownProperties": {}, "ownSymbols": [], "ownPropertiesLength": 1, "ownSymbolsLength": 0, "safeGetterValues": {} } } ``` I don't know what's going on in the Grip rep to print those 3 undefined properties, I'll have a look. In the meantime, we should fix the actor to actually send the __proto__ property in the preview.

Argh! The preview should inherit from null to avoid setters in Object.prototype! https://searchfox.org/mozilla-central/rev/efce4ceddfbe5fe4e2d74f1aed93894bada9b273/devtools/server/actors/object.js#1627

Ah, no, sorry, preview.ownProperties inherits from null indeed. I guess the object is later copied into an object which inherits from Object.prototype or something like this.

Nicolas, are you sure that's the packet? If I add a breakpoint in https://searchfox.org/mozilla-central/rev/33cc9e0331da8d9ff3750f1e68d72d61201176cb/devtools/client/shared/components/reps/reps.js#584 and run JSON.stringify(object, null, 2) then I get { "type": "object", "actor": "server1.conn1.child1/obj31", "class": "Object", "extensible": true, "frozen": false, "sealed": false, "ownPropertyLength": 1, "preview": { "kind": "Object", "ownProperties": { "__proto__": { "configurable": true, "enumerable": true, "writable": true, "value": { "type": "object", "actor": "server1.conn1.child1/obj32", "class": "Array", "extensible": true, "frozen": false, "sealed": false, "ownPropertyLength": 1, "preview": { "kind": "ArrayLike", "length": 0 } } } }, "ownSymbols": [], "ownPropertiesLength": 1, "ownSymbolsLength": 0, "safeGetterValues": {} } }

Right, I think I was targetting an old server, thanks Oriol

Fixed in GH https://github.com/devtools-html/devtools-core/pull/987

Fixed by bug 1440388. Now it's ▶ Object { __proto__: [] } And expanded: ▼ {...} | ▶ __proto__: Array [] However, I would prefer a more explicit ▼ {...} | ▶ __proto__: Array [] | <prototype>: null I will file a reps issue for that.