Ticket #42442: 42442.1.diff

src/wp-admin/js/customize-controls.js

@@ -3202 +3202 @@
                         }
 
                         // Prevent loading a non-active theme preview when there is a drafted/scheduled changeset.
-                        if ( panel.canSwitchTheme( slug ) ) {
+                        if ( ! panel.canSwitchTheme( slug ) ) {
                                 deferred.reject({
                                         errorCode: 'theme_switch_unavailable'
                                 });
@@ -3299 +3299 @@
 
                         // Prevent loading a non-active theme preview when there is a drafted/scheduled changeset.
                         if ( ! panel.canSwitchTheme( themeId ) ) {
-                                return deferred.reject().promise();
+                                deferred.reject({
+                                        errorCode: 'theme_switch_unavailable'
+                                });
+                                return deferred.promise();
                         }
 
                         urlParser = document.createElement( 'a' );

src/wp-includes/class-wp-customize-manager.php

@@ -5446 +5446 @@
                                 $theme->id           = $theme->slug;
                                 $theme->screenshot   = array( $theme->screenshot_url );
                                 $theme->authorAndUri = $theme->author;
-                                $theme->parent       = ( $theme->slug === $theme->template ) ? false : $theme->template; // The .org API does not seem to return the parent in a documented way; however, this check should yield a similar result in most cases.
+                                // The .org API can return the full parent theme details if passed the 'parent' arg, or if passed the 'template' option it'll return that in the event it's a child theme.
+                                if ( isset( $theme->parent ) ) {
+                                        $theme->parent = $theme->parent->slug;
+                                } else {
+                                        $theme->parent = false;
+                                }
                                 unset( $theme->slug );
                                 unset( $theme->screenshot_url );
                                 unset( $theme->author );