Does any browser still implement namespace-based dispatching?

[annevk]

In process a navigate response:

If [the XML document] section determines that the content is not to be displayed as a generic XML document, then proceed to the next step in this overall set of steps.

In the XML document section:

User agents may examine the namespace of the root Element node of this Document object to perform namespace-based dispatch to alternative processing tools, e.g. determining that the content is actually a syndication feed and passing it to a feed handler. If such processing is to take place, abort the steps in this section, and jump to the next step (labeled non-document content) in the navigate steps above.

While the jumping around is by itself worthy of a fix, I'm wondering whether any browser actually does this kind of namespace-based dispatching.

And if such namespace-based dispatching is to take place, should we really do it by creating a document first or just running the XML parser for a bit until we find an element?

[annevk]

If we fix #2657 this might be less problematic. We just end up generating a garbage document and potentially a garbage window.

[annevk]

It also seems this would require waiting for a root element to be found, which can potentially be a long time, before switching from the old to the new document. That seems problematic (and is not really accounted for event loop wise, as nothing says to go in parallel).

[annevk]

cc @hsivonen @tkent-google @cdumez

[tkent-google]

I don't think Blink has the namespace dispatch.

[domenic]

Firefox used to do this with RSS documents, I think? Before removing native RSS support. Could someone confirm it doesn't do it with any other types of XML documents?

It'd be ideal to get Safari to weigh in as well, just in case.

[Yay295]

I think Waterfox still suports RSS, so @MrAlex94 might know about that.

[annevk]

I did ask in Mozilla's #content IRC channel and peterv suggested Firefox doesn't have this.