typing "document.__proto__" in inspector throws exception > document.__proto__ file:///Users/eseidel/Projects/build/Debug/WebCore.framework/Resources/inspector/utilities.js:843TypeError: Result of expression 'this.nodeName' [undefined] is not an object.
After some digging it appears this is a rather weird edge case that can be reduced to this: > typeof document.__proto__ object > document.__proto__ instanceof window.Node true > document.__proto__.nodeName undefined > document.__proto__.nodeType undefined So when the formatter actually gets down to formating as a node, jumps into utilities.js's nodeTitleInfo(), does a switch on obj.nodeType (undefined) which hits the default case and tries obj.nodeName and throws the error. The Javascript workaround that I feel is the most responsible would be to treat "document.__proto__" as the type it returns via "typeof", which is "object", instead of "node". To be more general, if something is an "instanceof Node" then to really be sure its a node it should have a "nodeType" property. Otherwise its lieing! Maybe the solution is to change something in the Document C++ implementation so document.__proto__ instanceof "Node" returns false instead of true.
Created attachment 33317 [details] Javascript Workaround This would be the javascript workaround. I looked into what Firefox does and they don't report document.__proto__ as an instanceof Node! So maybe that would be the better route. WebKit via Web Inspector: > document.__proto__ instanceof window.Node true Firefox via Firebug: > document.__proto__ instanceof window.Node false
(In reply to comment #2) > This would be the javascript workaround. I looked into what Firefox does and > they don't report document.__proto__ as an instanceof Node! So maybe that > would be the better route. Opera returns false too. But I can't figure out why. From my understanding, the implementation of FOO instanceof BAR should be something like this function instanceof(FOO, BAR) { var o = FOO; while (o = o.__proto__) { if (o === BAR.prototype) return true; } return false; } And I think this is written in JSObject::hasInstance which implements [[hasInstance]] from the spec. WebCore's prototype chain looks like this document.__proto__ = HTMLDocumentPrototype document.__proto__. __proto__ = DocumentPrototype document.__proto__. __proto__. __proto__ = NodePrototype document.__proto__. __proto__. __proto__.__proto__ = Object And (Node.prototype === document.__proto__. __proto__. __proto__) is true So (document.__proto__ instanceof window.Node) returns true. In Firefox (Node.prototype === document.__proto__. __proto__. __proto__) is also true so I don't understand why Firefox is returning false for (document.__proto__ instanceof window.Node). Which is correct?
obj.nodeType === undefined would be best written as: typeof obj.nodeType === "undefined"
Did we decide there was a real bug here in either WebKit or Firefox? If so, we should file it...
(In reply to comment #5) > Did we decide there was a real bug here in either WebKit or Firefox? If so, we > should file it... Filed. https://bugs.webkit.org/show_bug.cgi?id=27611
Committing to http://svn.webkit.org/repository/webkit/trunk ... M WebCore/ChangeLog M WebCore/inspector/front-end/utilities.js Committed r46345 M WebCore/ChangeLog M WebCore/inspector/front-end/utilities.js r46345 = 1203ffee2d3ca9a82f4ecd7eecf5061b5a6091e0 (trunk) No changes between current HEAD and refs/remotes/trunk Resetting to the latest refs/remotes/trunk http://trac.webkit.org/changeset/46345