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Re: [whatwg] Spec for handling runtime script errors doesn't seem to match reality

From: Ian Hickson <ian@hixie.ch>
Date: Mon, 7 Jan 2013 19:34:13 +0000 (UTC)
To: Boris Zbarsky <bzbarsky@MIT.EDU>, Simon Pieters <simonp@opera.com>, "olli@pettay.fi" <olli@pettay.fi>
Message-ID: <Pine.LNX.4.64.1301071929420.16292@ps20323.dreamhostps.com>
Cc: whatwg <whatwg@lists.whatwg.org>
On Mon, 12 Nov 2012, Boris Zbarsky wrote:
>
> Consider the attached testcase, which calls setTimeout on a window and 
> passes in a function from a different window.

> <iframe></iframe>
> <script>
>     window.onload = function() {
>       window.onerror = function(msg, file, line) {
>         alert('Parent handler: ' + msg + " " + file + " " + line);
>       }
>       frames[0].onerror = function(msg, file, line) {
>         alert('Subframe handler: ' + msg + " " + file + " " + line);
>       }
>       frames[0].setTimeout(function() { throw "oops"; }, 100);
>     }
> </script>

> When this function is then called, it throws.
> 
> Gecko, WebKit, and Presto all seem to trigger the onerror handler of the 
> window setTimeout was called on in this case.
> 
> Per spec, section 7.1.3.5.1, we have:
> 
>   Whenever an uncaught runtime script error occurs in one of the
>   scripts associated with a Document, the user agent must report
>   the error at the URL of the resource containing the script (as
>   established when the script was created), with the problematic
>   position (line number and column number) in that resource, in
>   the script's origin, using the onerror event handler of the
>   script's global object.
> 
> But the global object is the window the function came from.  So the spec 
> doesn't seem to match any of the above three rendering engines.  Does it 
> match Trident?

On Mon, 12 Nov 2012, Boris Zbarsky wrote:
> 
> Looks like IE, in all the modes I can test, does what the spec says 
> right now.
> 
> I'll be changing Gecko to align with IE and the spec (and, arguably, 
> sanity) here.

Ok. I've left the spec as is here. Please do let me know if this is the 
wrong thing to do after all; I don't have any data on what is the more 
compatible behaviour and this stuff is subtle enough that I don't think 
sanity is necessarily unambiguously on the side of one answer or another.

-- 
Ian Hickson               U+1047E                )\._.,--....,'``.    fL
http://ln.hixie.ch/       U+263A                /,   _.. \   _\  ;`._ ,.
Things that are impossible just take longer.   `._.-(,_..'--(,_..'`-.;.'
Received on Monday, 7 January 2013 19:34:37 GMT

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