Browsers do not consistently seem to check this?

[annevk]

var x = Object.create(getComputedStyle(document.documentElement));
document.write('display: ' + x.display);

In Firefox x.display throws, but it does not in Chrome/Safari (it yields "block"). For a similar test with Location all browsers throw.

I thought that per 1.1.2.3.2 of https://heycam.github.io/webidl/#dfn-attribute-getter this throws, but perhaps I'm holding it wrong? Or maybe it's some magic with CSS2Properties that ends up violating IDL?

(Firefox: https://bugzilla.mozilla.org/show_bug.cgi?id=1315409.)

[domenic]

Or maybe it's some magic with CSS2Properties that ends up violating IDL?

This seems quite likely. From what I understand we're currently working on aligning CSS2Properties with Firefox: https://groups.google.com/a/chromium.org/g/blink-dev/c/MfR5PmnS77U . (Although that talks about CSSStyleDecoration? Not sure on the relation.) /cc @andruud

Testing Text instead gives the appropriate error in Chrome: http://software.hixie.ch/utilities/js/live-dom-viewer/?saved=8954

[andruud]

Yeah, we're working to align with Firefox in terms on exposing the property attributes (e.g. display) on the prototype rather than as "own" properties. Safari also made the same change actually, but reverted it due to binary size issues (details in the I2S).

Not sure on the relation.

CSS2Properties is non-standard Firefox thing which derives from CSSStyleDeclaration. Emilio is trying to standardize it, and we'll try to align when that happens. It's a separate issue from the I2S you linked to though.

[annevk]

I guess this can be closed then. Thanks everyone!

[andruud]

Correction: CSS2Properties apparently isn't a non-standard Firefox thing, it's just an obsolete representation from DOM2.

https://www.w3.org/TR/DOM-Level-2-Style/css.html#CSS-CSS2Properties

(In case this kept anyone awake at night).