[wp-trac] [WordPress Trac] #59316: Incorporate script loading strategies in bundled themes

[WordPress Trac]

#59316: Incorporate script loading strategies in bundled themes
---------------------------+--------------------------------------
 Reporter:  westonruter    |       Owner:  westonruter
     Type:  enhancement    |      Status:  reopened
 Priority:  normal         |   Milestone:  6.4
Component:  Bundled Theme  |     Version:  6.3
 Severity:  normal         |  Resolution:
 Keywords:  has-patch      |     Focuses:  javascript, performance
---------------------------+--------------------------------------

Comment (by westonruter):

 Replying to [comment:6 peterwilsoncc]:
 > Generally WP tries to keep bundled themes compatible with the WordPress
 version in which they were introduced. As an example of this, 2011 checks
 the [https://github.com/WordPress/wordpress-
 develop/blob/c696a2f773d9e5d61ea39e46f5d95f4442c63dfa/src/wp-
 content/themes/twentyeleven/inc/block-patterns.php block pattern functions
 exist] prior to calling them.
 >
 > I think these changes and those in #59302 will need to be modified to
 account for the older function signature.

 The function signature change from `bool` to `array|bool` was actually
 anticipating backwards-compatibility. For example, if someone does:

 {{{#!php
 <?php
 wp_enqueue_script(
     'foo',
     'https://example.org/foo.js',
     array(),
     false,
     array(
         'strategy' => 'defer',
         'in_footer' => false,
     )
 );
 }}}

 The array being passed in as `$in_footer` will result in WP<6.3 as the
 value being truthy and thus effectively being treated the same as `true`
 in both [https://github.com/WordPress/wordpress-
 develop/blob/52226e0308918474a0ac4ab8017e091ed3ae692a/src/wp-
 includes/functions.wp-scripts.php#L346-L351 wp_enqueue_script()] and
 [https://github.com/WordPress/wordpress-
 develop/blob/52226e0308918474a0ac4ab8017e091ed3ae692a/src/wp-
 includes/functions.wp-scripts.php#L173-L179 wp_register_script()]. The
 `defer` loading strategy is essentially the same behavior as
 `$in_footer=true` because execution happens at the end of the document
 loading in both cases. The enhancement for using `defer` here is that the
 script can start loading earlier, but if it loads later once encountered
 in the footer there isn't any functional difference.

 The only back-compat case where this doesn't work as expected is if the
 script has to be executed in the `head`, such as if they passed `array(
 'in_footer' => false )` without any strategy. However, this wasn't the
 case for any of the core themes: they were all already being printed in
 the footer (or in the case of Twenty Twenty, using a loading strategy;
 also see [https://github.com/WordPress/wordpress-
 develop/pull/5170/files#r1324822884 exception] in Twenty Eleven).

 So I don't see this as being a case where there is a backwards-
 compatibility break. Do you? I know @flixos90 has some additional
 thoughts.

-- 
Ticket URL: <https://core.trac.wordpress.org/ticket/59316#comment:10>
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