[wp-trac] [WordPress Trac] #42438: Add support for preload links (similar to resource hints)

[WordPress Trac]

#42438: Add support for preload links (similar to resource hints)
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 Reporter:  nico23                               |       Owner:  swissspidy
     Type:  enhancement                          |      Status:  closed
 Priority:  normal                               |   Milestone:  6.1
Component:  Script Loader                        |     Version:  4.9
 Severity:  normal                               |  Resolution:  fixed
 Keywords:  has-unit-tests has-patch commit      |     Focuses:
  needs-dev-note                                 |  performance
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Comment (by adamsilverstein):

 > What are the actual benefits of having a declarative API? I cannot
 imagine a scenario where the filter is insufficient to achieve what the
 developer wants.

 Good question @furi3r! This was proposed by @swissspidy who may want to
 weigh in here; in my mind this would be a cleaner way to declare the
 preload, especially for a script directly after adding it, adding via a
 filter works but is a bit messier.

 It doesn't add a new capability, rather a different way of using the
 already added capability.

 > If the function is added, maybe check if the wp_head action has fired
 and log a notice if that is the case.
 > Also this will fail if wp_add_preload_resources() is used after
 wp_preload_resources(), and the plugin using it will not even know. Worth
 mentioning in the docblock at least.

 Ah good point, we could fire a "doing_it_wrong" notice if the function is
 called after the headers were already output.

 > I'm not a fan of globals. It is the (very) old way of doing things and
 has many drawbacks

 Admittedly, I was following old patterns! How would you suggest building
 this? As a class variable? do we have similar code elsewhere in core to
 mimic?

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Ticket URL: <https://core.trac.wordpress.org/ticket/42438#comment:70>
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