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[Bug 18732] [Custom]: element upgrade algorithm does not preserve attributes, event listeners, references

From: <bugzilla@jessica.w3.org>
Date: Wed, 29 Aug 2012 17:14:03 +0000
Message-Id: <E1T6lq7-0007GG-Iv@jessica.w3.org>
To: public-webapps-bugzilla@w3.org

--- Comment #3 from Scott Miles <sjmiles@chromium.org> 2012-08-29 17:14:03 UTC ---
My understanding is that, If my document looks like this:

  <x-element important="important"><span>important goodies</span></x-element>

and my code does:

  x = document.querySelector("x-element");
  x.addEventListener("onclick", clickAction);

if the upgrade algorithm runs after the above code, the following effects

- the original x-element is replaced in DOM
- the new x-element has no onclick
- the new x-element has no 'important' attribute
- x-element's original children are lost (not in DOM)
- the x reference refers to a node that's no longer in DOM

The 'onclick' is lost (the old element is not in DOM, the new element doesn't
have that event). Any attempt to use the x reference to work with DOM will
simply not work (that node is not in DOM). Any query for 'important' x-elements
will not include the new element.

It's true that 'x' still references a node, but I don't see how it's useful.
That node is dangling and really should be GC'd asap.

I believe the alternative Steve mentions is to upgrade the element 'in place'
my modifying it's prototype and performing the rest of the upgrade steps on
this original element. In this case, the attributes, listeners, and references
are intact. This solution is also not ideal because we lose whatever the native
constructor would have done to the replacement element.

In any case, if the upgrade event is migrated to the new object, can't the
event simply be fired on the new object?

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Received on Wednesday, 29 August 2012 17:14:04 UTC

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