Reflecting as URL and failing to resolve

[zcorpan]

https://html.spec.whatwg.org/#reflecting-content-attributes-in-idl-attributes

If a reflecting IDL attribute is a DOMString attribute whose content attribute is defined to contain a URL, then on getting, the IDL attribute must resolve the value of the content attribute relative to the element and return the resulting absolute URL if that was successful, or the empty string otherwise

I'm not sure empty string is right. For a.href it returns the attribute's value instead:

https://html.spec.whatwg.org/multipage/semantics.html#dom-hyperlink-href

Also related is base href https://html.spec.whatwg.org/multipage/semantics.html#dom-base-href

http://software.hixie.ch/utilities/js/live-dom-viewer/saved/3843 - Gecko returns the attribute's value for both img src and base href.

I suggest we switch to that so it's consistent with a href.

cc @Ms2ger

[foolip]

For http://software.hixie.ch/utilities/js/live-dom-viewer/saved/3843 IE logs "http://[/" twice. It looks like interop for invalid URLs in base.href is as bad as it can be, so changing it should be low risk.

[zcorpan]

The IDL attributes that reflect as a URL are:

base href
link href
blockquote cite
a href
ins cite
del cite
img src
iframe src
embed src
object data
video poster
source src
track src
video src
area href
input src
form action
button formAction
input formAction
script src
applet object
frame src
frame longDesc
iframe longDesc
img longDesc
img lowsrc
object codeBase

(This would be easier to find and be confident about being correct if reflecting was using IDL syntax instead...)

[zcorpan]

a href and area href don't use "reflect"; https://html.spec.whatwg.org/#dom-hyperlink-href

[zcorpan]

Value is "x" http://software.hixie.ch/utilities/js/live-dom-viewer/saved/3995
Value is "//[" http://software.hixie.ch/utilities/js/live-dom-viewer/saved/3996
Attribute absent http://software.hixie.ch/utilities/js/live-dom-viewer/saved/3997