[wp-trac] [WordPress Trac] #64907: Script Modules: Import map can print after classic footer scripts in wp-admin, breaking bare specifier resolution

[WordPress Trac]

#64907: Script Modules: Import map can print after classic footer scripts in wp-
admin, breaking bare specifier resolution
---------------------------+-----------------------------
 Reporter:  mlaetitia      |      Owner:  (none)
     Type:  defect (bug)   |     Status:  new
 Priority:  normal         |  Milestone:  Awaiting Review
Component:  Script Loader  |    Version:
 Severity:  normal         |   Keywords:
  Focuses:  javascript     |
---------------------------+-----------------------------
 While testing the new Settings->Connectors and Appearance->Fonts screens
 we noticed that in some sites nothing was getting loaded and this error
 came up in the console:

 {{{
 TypeError: Failed to resolve module specifier '@wordpress/boot'
 }}}

 Both `_wp_footer_scripts` and `WP_Script_Modules::print_import_map` hook
 into `admin_print_footer_scripts` at priority 10. At the same priority,
 callbacks run in registration order. If a plugin loads `admin-filters.php`
 before `after_setup_theme` fires, `_wp_footer_scripts` registers first and
 classic scripts (including inline `import()` calls) print before the
 import map. The browser can't resolve bare specifiers without the import
 map already in the DOM.

 == Steps to reproduce ==

 1. Install WordPress 7.0-beta5
 2. Create a plugin with this code and activate it (or use Code Snippets):

 {{{#!php
 <?php
 /**
  * Plugin Name: Import Map Order Bug Reproducer
  */

 // Loading admin-filters.php during plugin init (before after_setup_theme)
 // causes _wp_footer_scripts to register on admin_print_footer_scripts
 // before the Script Modules system registers print_import_map.
 if ( is_admin() ) {
     require_once ABSPATH . 'wp-admin/includes/admin-filters.php';
 }
 }}}

 3. Go to Settings > Connectors or Appearance > Fonts
 4. Open the browser console — the page is broken with a bare specifier
 error

 Example: The Events Calendar does causes this through its bundled Action
 Scheduler/admin dependencies (the reason why we found this issue!). Other
 plugins that load admin utilities early will have the same effect.

 == Suggested fix ==

 `print_import_map` should hook at a priority that guarantees it runs
 before `_wp_footer_scripts`, regardless of registration order. For
 example, hooking `print_import_map` at priority 9  in class-wp-script-
 modules.php:358 would fix this:

 {{{#!php
 add_action( 'admin_print_footer_scripts', array( $this, 'print_import_map'
 ), 9 );
 }}}

 == Environment ==

  * WordPress 7.0-beta5 (build 62069)
  * Reproducible with The Events Calendar 6.15.17.1 or the minimal code
 snippet above (can be reproduced in Playground)
  * Tested locally on macOS/Valet
  * Affects both the Connectors screen and the Font Library screen

-- 
Ticket URL: <https://core.trac.wordpress.org/ticket/64907>
WordPress Trac <https://core.trac.wordpress.org/>
WordPress publishing platform