[wp-trac] [WordPress Trac] #41488: Customize: uncaught JS error with namespaced nav menu fallbacks

[WordPress Trac]

#41488: Customize: uncaught JS error with namespaced nav menu fallbacks
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 Reporter:  dlh           |       Owner:
     Type:  defect (bug)  |      Status:  new
 Priority:  normal        |   Milestone:  4.9
Component:  Customize     |     Version:  4.3
 Severity:  normal        |  Resolution:
 Keywords:  has-patch     |     Focuses:
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Comment (by westonruter):

 @dlh yeah, I can see that the JSON is getting corrupted. To illustrate
 that the problem resides in slashing, try adding this patch:

 {{{#!diff
 --- src/wp-includes/class-wp-customize-nav-menus.php
 +++ src/wp-includes/class-wp-customize-nav-menus.php
 @@ -1271,7 +1271,7 @@ final class WP_Customize_Nav_Menus {
                 if ( isset(
 $args->customize_preview_nav_menus_args['can_partial_refresh'] ) &&
 $args->customize_preview_nav_menus_args['can_partial_refresh'] ) {
                         $attributes = sprintf( ' data-customize-partial-
 id="%s"', esc_attr( 'nav_menu_instance[' .
 $args->customize_preview_nav_menus_args['args_hmac'] . ']' ) );
                         $attributes .= ' data-customize-partial-
 type="nav_menu_instance"';
 -                       $attributes .= sprintf( ' data-customize-partial-
 placement-context="%s"', esc_attr( wp_json_encode(
 $args->customize_preview_nav_menus_args ) ) );
 +                       $attributes .= sprintf( ' data-customize-partial-
 placement-context="%s"', wp_slash( esc_attr( wp_json_encode(
 $args->customize_preview_nav_menus_args ) ) ) );
                         $nav_menu_content = preg_replace( '#^(<\w+)#', '$1
 ' . $attributes, $nav_menu_content, 1 );
                 }
                 return $nav_menu_content;

 }}}

 You'll see that by wrapping the escaped attribute in `wp_slash`, it
 prevents the slashes from getting dropped. Somewhere somehow there is
 `wp_unslash()` or `stripslashes()` that is causing the JSON string
 `"\\WordPress\\my_callback"` to become the invalid
 `"\WordPress\my_callback"`.

 This is the underlying issue that needs to be fixed.

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Ticket URL: <https://core.trac.wordpress.org/ticket/41488#comment:3>
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