[wp-trac] [WordPress Trac] #64150: Late-printed styles are not hoisted to HEAD if wp-block-library is not enqueued

[WordPress Trac]

#64150: Late-printed styles are not hoisted to HEAD if wp-block-library is not
enqueued
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 Reporter:  westonruter               |       Owner:  westonruter
     Type:  defect (bug)              |      Status:  closed
 Priority:  normal                    |   Milestone:  6.9
Component:  Script Loader             |     Version:  6.9
 Severity:  normal                    |  Resolution:  fixed
 Keywords:  has-patch has-unit-tests  |     Focuses:  performance
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Comment (by westonruter):

 In [changeset:"61945" 61945]:
 {{{
 #!CommitTicketReference repository="" revision="61945"
 Script Loader: Refine hoisted stylesheet ordering to preserve original CSS
 cascade in classic themes.

 This introduces placeholder inline `STYLE` tags in the `HEAD` which are
 used to accurately locate hoisted styles which were printed in the footer.
 This improves the robustness of the hoisting logic. A style placeholder
 had been used previously in the inline style for `wp-block-library` for
 placing core block styles, and new placeholders are added for global
 styles and non-core block styles.

 Furthermore, this fixes the cascade for inline styles added to `wp-block-
 library`. When separate block styles are not used, these styles would have
 appeared after the single combined `wp-block-library`. However, in 6.9 the
 order changed so that separate block styles would appear after. To
 preserve the original cascade, this splits the `wp-block-library` inline
 style: the first half (likely just the inlined `block-library/common.css`)
 appears before the block styles, and the remainder appears in a new `STYLE
 #wp-block-library-inline-css-extra` element.

 Developed in https://github.com/WordPress/wordpress-develop/pull/10875

 Follow-up to r61554, r61174, r61122, r61076, r61008.

 Props westonruter, joefusco, adamsilverstein, ocean90, mmorris8, ozgursar,
 vanonsopensource, xwolf, immeet94, george9, joezappie, jorbin, sajib1223,
 sabernhardt.
 See #64099, #64354, #64150, #43258.
 Fixes #64389.
 }}}

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Ticket URL: <https://core.trac.wordpress.org/ticket/64150#comment:23>
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