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[whatwg] Script/parser interaction bug?

From: Kartikaya Gupta <lists.whatwg@stakface.com>
Date: Thu, 12 Feb 2009 22:25:04 +0000
Message-ID: <20090212222514.C75B314D91B@looneymail-mx2.g.dreamhost.com>
On Thu, 12 Feb 2009 06:55:18 +0000 (UTC), Ian Hickson <ian at hixie.ch> wrote:
> 
> Could you reannotate the above but with the script nesting level 
> explicitly given at each step?
> 


Below is an updated annotation including all the script nesting level and parser pause flag changes.
(Original annotation at http://lists.whatwg.org/pipermail/whatwg-whatwg.org/2009-January/018289.html)

- initially, script nesting level is zero, parser pause flag is false
- tokenize/treebuild ext7.html until the first closing script tag is found (for the 7a.js script)
- increment the script nesting level to 1
- the 7a.js script tag has a src attribute, so it gets set as the pending external script
- decrement the script nesting level to zero
- since the script nesting level is zero, set the parser pause flag to false (it was already false)
- execute the pending external script (7a.js) (this clears the pending external script pointer)
--- insert "<script src=ext7b.js></script>" into the input stream
--- tokenize/treebuild the 7b.js script tag until the </script> for 7b.js is found
--- increment the script nesting level to 1
--- the 7b.js script tag has a src attribute, so it gets set as the pending external script
--- decrement the script nesting level to zero
--- since the script nesting level is zero, set the parser pause flag to false (it was already false)
--- there is a pending external script (7b.js) but the tree construction stage is re-entrant, so set parser pause flag to true and return
--- insert remaining document.write content from 7a.js into the input stream. since there is a pending external script, none of it gets tokenized/treebuilt
- 7a.js finishes executing. at this point the script nesting level is zero and the parser pause flag is true
- check again for a pending external script. there is one, 7b.js
- execute the pending external script (7b.js) (this clears the pending external script pointer)
--- throws
- 7b.js finishes executing. at this point the script nesting level is zero and the parser pause flag is true
- continue processing the input stream (this now has the contents of the document.write calls from 7a.js, line 2 onwards)
- tokenize/treebuild the input stream until the </script> at the bottom of 7a.js is encountered
- increment the script nesting level to 1
- the script tag does not have a src attribute, so it gets executed
--- insert the div into the input stream
--- since the parser pause flag is true the div does NOT get tokenized/treebuilt
--- run the line that sets .firstChild.data to PASS. since the div isn't in the DOM yet, this throws
- the script written from 7a.js finishes executing. at this point the script nesting level is 1 and the parser pause flag is true
- decrement the script nesting level to zero
- since the script nesting level is zero, set the parser pause flag to false
- continue processing the input stream (this now contains just the div tag with FAIL inside)
- tokenize/treebuild the input stream, which adds the FAIL div to the DOM
- done

Cheers,
kats
Received on Thursday, 12 February 2009 14:25:04 UTC

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