Ticket #53410: 53410.2.diff

src/wp-admin/customize.php

@@ -184 +184 @@
                         <?php
                         $compatible_wp  = is_wp_version_compatible( $wp_customize->theme()->get( 'RequiresWP' ) );
                         $compatible_php = is_php_version_compatible( $wp_customize->theme()->get( 'RequiresPHP' ) );
+                        $fse_safe       = true;
+
+                        // Check if the theme requires the FSE to work correctly.
+                        $theme_tags = $wp_customize->theme()->get( 'Tags' );
+
+                        if ( ! empty( $theme_tags ) && in_array( 'full-site-editing', $theme_tags, true ) && ! is_plugin_active( 'gutenberg/gutenberg.php' ) ) {
+                                $fse_safe = false;
+                        }
                         ?>
-                        <?php if ( $compatible_wp && $compatible_php ) : ?>
+                        <?php if ( $compatible_wp && $compatible_php && $fse_safe ) : ?>
                                 <?php $save_text = $wp_customize->is_theme_active() ? __( 'Publish' ) : __( 'Activate &amp; Publish' ); ?>
                                 <div id="customize-save-button-wrapper" class="customize-save-button-wrapper" >
                                         <?php submit_button( $save_text, 'primary save', 'save', false ); ?>

src/wp-includes/theme.php

@@ -908 +908 @@
 function validate_theme_requirements( $stylesheet ) {
         $theme = wp_get_theme( $stylesheet );
 
+        // If the theme is a Full Site Editing theme, check for the presence of the Gutenberg plugin.
+        $theme_tags = $theme->get( 'Tags' );
+
+        if ( ! empty( $theme_tags ) && in_array( 'full-site-editing', $theme_tags, true ) && ! is_plugin_active( 'gutenberg/gutenberg.php' ) ) {
+                return new WP_Error(
+                        'theme_requires_fse',
+                        sprintf(
+                                        /* translators: %s: Theme name. */
+                                _x( '<strong>Error:</strong> This theme (%s) uses Full Site Editing, which requires the Gutenberg plugin to be activated.', 'theme' ),
+                                $theme->display( 'Name' )
+                        )
+                );
+        }
+
         $requirements = array(
                 'requires'     => ! empty( $theme->get( 'RequiresWP' ) ) ? $theme->get( 'RequiresWP' ) : '',
                 'requires_php' => ! empty( $theme->get( 'RequiresPHP' ) ) ? $theme->get( 'RequiresPHP' ) : '',