Recurse over explicit lists and data.frames

Fixes #466
Avoids recursion of list-like objects that aren't actually lists.
Recursion over data.frames is uncommon but was previously
supported and can, in theory, contain `JS()` calls in list columns.

R/utils.R

@@ -161,7 +161,7 @@ JSEvals <- function(list) {
 #' @noRd
 #' @keywords internal
 shouldEval <- function(options) {
-  if (is.list(options)) {
+  if (inherits(options, c("list", "data.frame"))) {
     if ((n <- length(options)) == 0) return(FALSE)
     # use numeric indices as names (remember JS indexes from 0, hence -1 here)
     if (is.null(names(options)))