843881 - createElement image returns HTMLElement instead of HTMLUnknownElement

Status: NEW

(Core :: DOM: Core & HTML, defect, P5)

Description

[Erik Arvidsson]

The following fails

assert(document.createElement('image').constructor === HTMLImageElement);
assert(document.createElement('image').constructor !== HTMLSpanElement);

It is really confusing to get an HTMLSpanElement out of this

Comment 1

[Kyle Huey (Exited; not receiving bugmail, old account, do not use)]

We've had this behavior for a decade.  Not really sure why.

Comment 2

[Kyle Huey (Exited; not receiving bugmail, old account, do not use)]

Maybe we used to use span for what now is just a generic html element?

Comment 3

[Olli Pettay [:smaug][[e-mail]]]

Henri might remember.
image is odd element.

Comment 4

[Boris Zbarsky [:bzbarsky]]

"image" is not special for purposes of createElement.  It's just like "foo" or "xyzw" or "noSuchElementName".

So we should be creating an HTMLUnknownElement here, as far as I can tell (but aren't, for silly historical reasons that predate the existence of HTMLUnknownElement as I recall).  We should consider going through nsHTMLTagList.h and fixing up the various things that claim "Span" for the second argument; some of these should be HTMLUnknownElement and some apparently actually have interfaces for them in HTML5 (basefont???).

Comment 5

[:Ms2ger (he/him; ⌚ UTC+1/+2)]

(In reply to Erik Arvidsson from comment #0)
> The following fails
> 
> assert(document.createElement('image').constructor === HTMLImageElement);

This should fail. That it doesn't is a bug in WebKit.

Comment 6

[Henri Sivonen (:hsivonen)]

(In reply to :Ms2ger from comment #5)
> (In reply to Erik Arvidsson from comment #0)
> > The following fails
> > 
> > assert(document.createElement('image').constructor === HTMLImageElement);
> 
> This should fail. That it doesn't is a bug in WebKit.

document.createElement("image"); results in an HTMLImageElement in IE10, too. Maybe we should just align instead of fighting it. Need more testing first to see if such elements actually work in WebKit and IE.

Comment 7

[Boris Zbarsky [:bzbarsky]]

ccing Anne, since this would need domcore spec changes to create an element with localName "img" when createElement("image") is called...  At least that's what WebKit does, so I would expect that it "works" just fine once created.

Comment 8

[Anne (:annevk)]

Not just createElement() it seems. :-(

http://software.hixie.ch/utilities/js/live-dom-viewer/

<script>w(document.createElementNS("http://www.w3.org/1999/xhtml", "image"))</script>

Maybe the conceptual model should be that the local name and namespace are decided by the class that is mapped to. Might also work better for custom elements.

Comment 9

[Boris Zbarsky [:bzbarsky]]

> Not just createElement() it seems. :-(

Just in WebKit, or in IE10 too?

Comment 10

[Anne (:annevk)]

IE9 at least, cannot test IE10.

Comment 11

[Boris Zbarsky [:bzbarsky]]

So maybe we should spin off a separate bug on our use of "Span" when we should use "Unknown", independent of what happens with the "image" mess?  Or spin the "image" mess into a separate bug, either way.

Comment 12

[Anne (:annevk)]

Filed bug 844127 on Span vs Unknown. Removing good first bug flags as we first need to decide whether we want the "image" "magic" or not.