[wp-trac] [WordPress Trac] #42558: Reduce the number of capability checks performed by the Customizer

[WordPress Trac]

#42558: Reduce the number of capability checks performed by the Customizer
-------------------------+-----------------------------
 Reporter:  johnbillion  |      Owner:
     Type:  enhancement  |     Status:  new
 Priority:  normal       |  Milestone:  Awaiting Review
Component:  Customize    |    Version:
 Severity:  normal       |   Keywords:  needs-patch
  Focuses:  performance  |
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 On a vanilla installation of WordPress running the Twenty Seventeen theme,
 the Customizer performs over 400 user capability checks via
 `current_user_can()`.

 The majority of these are duplicate checks performed for each customizer
 setting. This includes:

 * ~140 calls to `current_user_can( 'customize' )`
 * ~220 calls to `current_user_can( 'edit_theme_options' )`
 * ~20 calls to `current_user_can( 'manage_options' )`

 The main offenders are:

 * `WP_Customize_Manager->unsanitized_post_values()`
 * `WP_Customize_Setting->check_capabilities()`
 * `WP_Customize_Section->check_capabilities()`
 * `WP_Customize_Panel->check_capabilities()`

 Calls to `current_user_can()` are quite cheap, but they're certainly not
 free, especially on sites which have filters hooked onto the
 `map_meta_cap` and `user_has_cap` filters, and sites with extra Customizer
 controls registered.

 With a static property cache in each of the `WP_Customize_Manager`,
 `WP_Customize_Section`, and `WP_Customize_Setting` classes, the 400
 capability checks are reduced to fewer than 30.

 Patch coming up soon, after some more testing.

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Ticket URL: <https://core.trac.wordpress.org/ticket/42558>
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