Clarify using CDATA in HTML context

[SetTrend]

What is the issue with the HTML Standard?

Currently, the HTML standard doesn't get clear on whether a <![CDATA[ ]]> section may be used in HTML context:

https://html.spec.whatwg.org/multipage/syntax.html#cdata-sections

There is just an example that – speaking only for the example itself – claims "CDATA sections can only be used in foreign content (MathML or SVG)."

Is this statement true for HTML? Then it should be moved outside the example heading.

[domenic]

Per spec it's a conformance error; see https://html.spec.whatwg.org/multipage/parsing.html#markup-declaration-open-state.

I agree that this should probably be stated somewhere near where you list, instead of just inside the parser. I'm not really sure what the best conventions are for this sort of duplicate conformance requirement, but I know we have a variety of them.

I guess this is already implicit in https://html.spec.whatwg.org/#elements-2 actually?

The contents of the element must be placed between just after the start tag (which might be implied, in certain cases) and just before the end tag (which again, might be implied in certain cases). The exact allowed contents of each individual element depend on the content model of that element, as described earlier in this specification.

and no content models allow CDATA sections.

But yeah, your idea of just moving this sentence outside of the example might be reasonable.

[annevk]

I think it could be a note instead of being part of the example, but we probably wouldn't want to restate it normatively as it indeed already follows from where it is referenced?

[domenic]

@annevk, I thought you were the one who generally argued for the duplicate-normative-conformance-requirements approach, per whatwg/url#704 (comment) ?