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Re: Cleaning House

From: Philip Taylor <philip@zaynar.demon.co.uk>
Date: Thu, 03 May 2007 14:42:55 +0200
To: www-html@w3.org
Message-ID: <4639D7EA.20806@zaynar.demon.co.uk>




Lachlan Hunt wrote:
> David Woolley wrote:
>> [...] HTML4 requires that the document be valid with orwithout the  
>> document.writes executed, but I think the HTML5 rules allowthe script  
>> to generate unbalanced tags.
> No it doesn't.  Why would you assume such a thing?

Since it's not entirely obvious, it might be helpful to show how the
HTML5 rules don't allow that.

My understanding is that a document like

      <!DOCTYPE HTML>
      <title></title>
      <p>
      <script>document.write('<b>Hello world');</script>

is non-conforming because:

* Document conformance is unrelated to whether a certain UA has
scripting enabled (this isn't stated anywhere that I can find, but I
think it's a valid belief), hence it is safe to assume scripting is  
enabled.

* The input stream tokenises all the tags up to and including the  
</script>.

* Simultaneously, the parsing algorithm inserts elements into the document.

* Because scripting is enabled, when the script element is inserted, the
script is executed.

* "<b>Hello world" is appended to the input stream at its current
insertion point (just after the </script>).

* The tokenising and parsing algorithms continue with the new input stream.

* The parsing algorithm reaches the end of the document, and the lack of
</b> causes a parse error.

* (I can't actually see an explicit mention that documents must not
cause parse errors - only that conformance checkers should (or, if it
happens when scripting is disabled, must) report a parse error. But I
think it's fairly obvious that such documents are meant to be considered
non-conforming, even if it might need clarification.)

Given the first point (that document conformance is unrelated to whether
scripting is enabled), I believe that also means

      <!DOCTYPE HTML>
      <title></title>
      <p>
      <script>document.write('<b>Hello world');</script>
      </b>

is non-conforming (even though it would not cause any parse errors in a
UA with scripting enabled).

But I believe scripts can technically still generate unbalanced tags,
because

      <!DOCTYPE HTML>
      <title></title>
      <p>
      <script>document.write('<b>Hello');</script>
      <script>document.write('world</b>');</script>

would be conforming regardless of whether scripting is enabled.

-- 
Philip Taylor
philip@zaynar.demon.co.uk
Received on Monday, 7 May 2007 15:20:59 GMT

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