Clarification on Document-createElementNS testcase

[minghuaw]

For the test case below, why would it accept an empty string as the expected value for 'element.prefix' instead of a null?

wpt/dom/nodes/Document-createElementNS.js

Line 42 in fee00f9

["", ":foo", null],

wpt/dom/nodes/Document-createElementNS.html

Line 69 in fee00f9

assert_equals(element.prefix, names[0], 'element.prefix')

I'm asking this because the spec as of today (https://dom.spec.whatwg.org/#valid-namespace-prefix) states that an empty string is NOT a valid namespace prefix. If the expected prefix extracted from ":foo" is an empty string "", shouldn't this test case expect an exception then?

[minghuaw]

Or I guess the problem really is caused by the line 64 in the code snippet below.

wpt/dom/nodes/Document-createElementNS.html

Lines 63 to 66 in fee00f9

	if (firstColonIndex >= 0) {
	names.push(qualified.substring(0, firstColonIndex));
	names.push(qualified.substring(firstColonIndex + 1));
	} else {

Simply using the .substring would include an empty string as the expected value while an empty string should not be a valid token generated from the strictly split algorithm https://infra.spec.whatwg.org/#strictly-split. The spec of the algorithm states that

3. Let token be the result of collecting a sequence of code points that are not equal to delimiter from input, given position.

and an empty string does NOT contain any codepoint as defined in the infra spec here https://infra.spec.whatwg.org/#code-point

[shannonbooth]

Hi, see whatwg/dom#1387