Fix null handling of HTMLSelectElement.value attribute

[Chris Dumez]

Fix null handling of HTMLSelectElement.value attribute:
https://html.spec.whatwg.org/multipage/forms.html#htmlselectelement

We currently treat null as the null String which ends up setting selectedIndex to -1. However, we should treat null as the String "null" which would set the selectedIndex to the Index of the <option> element whose value is "null".

Firefox and Chrome match the specification.

[Chris Dumez]

Created attachment 284019 [details]
Patch

[Benjamin Poulain]

Comment on attachment 284019 [details]
Patch

View in context: https://bugs.webkit.org/attachment.cgi?id=284019&action=review

> LayoutTests/fast/dom/HTMLSelectElement/value-null-handling.html:19
> +evalAndLog("select.value = null");
> +shouldBeEqualToString("select.value", "null");
> +shouldBe("select.selectedIndex", "1");

You are missing a case. Setting the value to null and not having a value==="null" in the select element.

[Chris Dumez]

Committed r203456: <http://trac.webkit.org/changeset/203456>

[Chris Dumez]

(In reply to comment #2)
> Comment on attachment 284019 [details]
> Patch
> 
> View in context:
> https://bugs.webkit.org/attachment.cgi?id=284019&action=review
> 
> > LayoutTests/fast/dom/HTMLSelectElement/value-null-handling.html:19
> > +evalAndLog("select.value = null");
> > +shouldBeEqualToString("select.value", "null");
> > +shouldBe("select.selectedIndex", "1");
> 
> You are missing a case. Setting the value to null and not having a
> value==="null" in the select element.

I added it before landing, thanks.