[wp-trac] [WordPress Trac] #38650: Provide some guidance on what conditionals can/should be used in default-filters.php

[WordPress Trac]

#38650: Provide some guidance on what conditionals can/should be used in default-
filters.php
----------------------------+---------------------
 Reporter:  helen           |       Owner:  jorbin
     Type:  enhancement     |      Status:  closed
 Priority:  low             |   Milestone:  6.7
Component:  Bootstrap/Load  |     Version:
 Severity:  minor           |  Resolution:  fixed
 Keywords:  has-patch       |     Focuses:
----------------------------+---------------------
Changes (by maqboolahmed5243):

 * focuses:  docs =>


Comment:

 You're absolutely right, the limitations in default-filters.php can be
 confusing, especially with functions like get_option() and
 is_customize_preview() not being safe to use directly. The file's role
 isn't immediately clear, and without a good understanding of how load
 sequences work, it’s easy to run into issues.

 An inline comment explaining the purpose of the file and outlining safe
 functions (like those from load.php) would definitely be helpful for
 anyone unfamiliar with the internals. This could prevent a lot of trial
 and error. Thanks for pointing this out—it’s a solid suggestion to improve
 clarity!
 {{{#!php
 <?php
 /**
  * default-filters.php
  *
  * This file registers the default filters and actions essential to
 WordPress
  * core functionality. It’s loaded very early in the WordPress
 bootstrapping
  * process, before many core components and settings are available.
  *
  * Safe to use:
  * - Functions and conditionals defined in load.php (e.g., is_admin(),
 current_user_can()).
  * - Low-level hooks and actions that don't rely on options, query
 variables, or themes.
  *
  * Unsafe to use:
  * - get_option(), get_theme_mod(), or anything that interacts with the
 options table.
  * - Conditional tags like is_singular(), is_page(),
 is_customize_preview(), etc.,
  *   which depend on query variables, the theme, or customizer data.
  *
  * Important: Stick to lightweight logic that doesn't require full
 WordPress
  * initialization. Defer more complex operations to later hooks, such as
  * after_setup_theme or init.
  */

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Ticket URL: <https://core.trac.wordpress.org/ticket/38650#comment:7>
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