[wp-trac] [WordPress Trac] #42438: preload is missing from ressource hints.

[WordPress Trac]

#42438: preload is missing from ressource hints.
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 Reporter:  nico23                        |       Owner:  swissspidy
     Type:  defect (bug)                  |      Status:  assigned
 Priority:  normal                        |   Milestone:  5.0
Component:  Script Loader                 |     Version:  4.9
 Severity:  normal                        |  Resolution:
 Keywords:  needs-unit-tests needs-patch  |     Focuses:
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Comment (by westonruter):

 I just ran across this as I was looking to add `<link rel="preload"
 as="script" href="https://cdn.ampproject.org/v0.js">` to the AMP plugin.

 While preload != resource hints it seems the existing resource hints API
 in WordPress is well suited for preload. For example, with
 [attachment:"add_preload_to_ressource_hints.patch"]:

 {{{#!php
 <?php
 add_filter( 'wp_resource_hints', function( $urls, $relation_type ) {
         if ( 'preload' === $relation_type ) {
                 $urls[] = array(
                         'rel'  => 'preload',
                         'as'   => 'script',
                         'href' => 'https://cdn.ampproject.org/v0.js',
                 );
         }
         return $urls;
 }, 10, 2 );
 }}}

 @igrigorik Would this be bad?

 As for the `pr` attribute in `wp_resource_hints()`, it's just allowing for
 the attribute to be used, it doesn't mandate it. We could add a special
 condition to `_doing_it_wrong()` if that attribute is provided. Likewise,
 we could call `_doing_it_wrong()` if the `as` attribute is used with
 anything other than `rel=preload`.

 Also, does it matter the order of the links? Should `preload` links come
 after resource hint links?

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Ticket URL: <https://core.trac.wordpress.org/ticket/42438#comment:5>
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