"DataCloneError: The object could not be cloned." is not a really helpful message. What part of my object could not be cloned? Or is it the transferable list that is somehow wrong? Several times, I have found myself spending literally hours trying to find out why my object is not clonable. I would really like more helpful messages.
This would require some JS side assistance.
Assignee: nobody → general
Also, note that this specific patch only touches DOM code. I presume the "JS side assistance" khuey is referencing has to do with getting structured cloning to maintain some type of path traversal information and/or having the error type carry a string payload? (Maybe also the XPConnect classes? There seem to be classes involved instead of just bare integer NSRESULTs these days, so maybe things are less hopeless than they used to be when it comes to errors.)
Right, it means that we don't know where the thing we're failing to clone is in relation to the root. Also note that it's possible for cloning to fail for reasons other than just "unrecognized type" (e.g. you can't clone a Function) and Gecko will not get called about those.
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