[wp-trac] [WordPress Trac] #43258: Output buffer template rendering and add filter for post-processing (e.g. caching, optimization)

[WordPress Trac]

#43258: Output buffer template rendering and add filter for post-processing (e.g.
caching, optimization)
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 Reporter:  nextendweb                           |       Owner:
                                                 |  westonruter
     Type:  enhancement                          |      Status:  closed
 Priority:  normal                               |   Milestone:  6.9
Component:  General                              |     Version:
 Severity:  normal                               |  Resolution:  fixed
 Keywords:  has-patch has-unit-tests dev-        |     Focuses:  docs,
  feedback                                       |  performance
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Changes (by westonruter):

 * status:  accepted => closed
 * resolution:   => fixed


Comment:

 In [changeset:"60936" 60936]:
 {{{
 #!CommitTicketReference repository="" revision="60936"
 General: Introduce output buffering for template enhancements.

 This introduces an output buffer for the entire template rendering
 process. This allows for post-processing of the complete HTML output via
 filtering before it is sent to the browser. This is primarily intended for
 performance optimizations and other progressive enhancements. Extenders
 must not rely on output buffer processing for critical content and
 functionality since a site may opt out of output buffering for the sake of
 streaming. Extenders are heavily encouraged to use the HTML API as opposed
 to using regular expressions in output buffer filters.

 * A new `wp_before_include_template` action is introduced, which fires
 immediately before the template file is included. This is useful on its
 own, as it avoids the need to misuse `template_include` filter to run
 logic right before the template is loaded (e.g. sending a `Server-Timing`
 header).
 * The `wp_start_template_enhancement_output_buffer()` function is hooked
 to this new action. It starts an output buffer, but only if there are
 `wp_template_enhancement_output_buffer` filters present, or else if there
 is an explicit opt-in via the
 `wp_should_output_buffer_template_for_enhancement` filter.
 * The `wp_finalize_template_enhancement_output_buffer()` function serves
 as the output buffer callback. It applies
 `wp_template_enhancement_output_buffer` filters to the buffered content if
 the response is identified as HTML.
 * The output buffer callback passes through (without filtering) any
 content for non-HTML responses, identified by the `Content-Type` response
 header.
 * This provides a standardized way for plugins (and core) to perform
 optimizations, such as removing unused CSS, without each opening their own
 ad hoc output buffer.

 Developed in https://github.com/WordPress/wordpress-develop/pull/8412.

 Props westonruter, nextendweb, dmsnell, flixos90, jorbin, peterwilsoncc,
 swissspidy, DrewAPicture, DaanvandenBergh, OptimizingMatters, tabrisrp,
 jonoaldersonwp, SergeyBiryukov.
 Fixes #43258.
 }}}

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Ticket URL: <https://core.trac.wordpress.org/ticket/43258#comment:68>
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