Resource hinting: only dns-prefetch enqueued resources.

[peterwilsoncc]

dns-prefetch link elements are currently created for all registered depenedencies, only create them for enqueued dependencies.

[swissspidy]

Isn't there already a fix for that in another ticket? Can't find it right now though.

[peterwilsoncc]

code: swissspidy, tests: peterwilsoncc

[peterwilsoncc]

@swissspidy there is in #34292 but forking it because it's become a bit of a super ticket.

I've brought the code across in 37385.diff​, props due are code: @swissspidy, tests: @peterwilsoncc

[peterwilsoncc]

In 38100:

Script Loader: Limit resource hinting to enqueued assets.

Externally hosted script and style dependencies trigger dns-prefetch hinting only when enqueued. This removed a bug in which hinting was added on registration.

Renames the function wp_resource_hints_scripts_styles to wp_dependencies_unique_hosts as the function provides the hosts, not the hinting.

Props swissspidy.
Fixes #37385.

[swissspidy]

Should the function be called wp_get_dependencies_unique_hosts() as suggested in 50:ticket:34292?

[peterwilsoncc]

Replying to swissspidy:

Should the function be called wp_get_dependencies_unique_hosts() as suggested in 50:ticket:34292?

I'm am not sure.

I think of the get_ and the_ prefixes as being somehow different but I can not explain how so succinctly. The prefixes put me in mind of WP objects, usually posts, whereas wp_[get_]dependencies_unique_hosts works at a higher level within WordPress itself.

As I say, I am not sure.