[wp-trac] [WordPress Trac] #59551: Respect non-null values from the `pre_render_block` filter

[WordPress Trac]

#59551: Respect non-null values from the `pre_render_block` filter
--------------------------+------------------------------
 Reporter:  danieliser    |       Owner:  (none)
     Type:  defect (bug)  |      Status:  new
 Priority:  normal        |   Milestone:  Awaiting Review
Component:  Editor        |     Version:  6.0
 Severity:  normal        |  Resolution:
 Keywords:                |     Focuses:
--------------------------+------------------------------
Changes (by jeremyfelt):

 * version:   => 6.0
 * component:  General => Editor


Comment:

 IMO, the general promise with `pre_` filters in core is that I can short-
 circuit something entirely.

 In `pre_render_block`'s current form, if I `add_filter(
 'pre_render_block', '__return_empty_string', 1 );`, I would expect that
 all blocks are rendered as an empty string.

 Because core's own use of `pre_render_block` does not respect the value of
 `$pre_render` set earlier than priority 10, the filter doesn't work as
 promised. Instead, I need to set my priority so that it runs after core.

 If I shift my priority to 11, and acknowledge that core will always
 process this block before I decide alter its output, then core will always
 prepare styles that I may not need via
 `wp_render_elements_support_styles()` and
 `_wp_add_block_level_preset_styles()`. That's somewhat annoying, but not
 as annoying as the block continuing to render. :)

 It seems that if these two functions are treating `pre_render_block` as an
 action rather than a filter, they should pass through the value of
 `$pre_render` untouched rather than force it to always be `null`. That's
 the patch I would propose here.

 I agree with @danieliser that the style processing should ideally not run
 at all if `! is_null( $pre_render )`, but I also understand the
 complication here. I'm not sure what a way forward to solve this looks
 like other than removing those hooks whenever my pre_render filters
 something.

-- 
Ticket URL: <https://core.trac.wordpress.org/ticket/59551#comment:4>
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