Ticket #39032: 39032.4.diff

src/wp-includes/theme.php

@@ -1786 +1786 @@
                 $r = wp_update_post( wp_slash( $post_data ), true );
         } else {
                 $r = wp_insert_post( wp_slash( $post_data ), true );
+
+                // Trigger creation of a revision. See #30854.
+                if ( ! is_wp_error( $r ) && 0 === count( wp_get_post_revisions( $r ) ) ) {
+                        wp_save_post_revision( $r ); // Trigger creation of a revision. See #30854.
+                }
         }
 
-        if ( $r instanceof WP_Error ) {
+        if ( is_wp_error( $r ) ) {
                 return $r;
         }
         return get_post( $r );