Fix rendering vctrs::list_of columns

DESCRIPTION

@@ -50,7 +50,8 @@ Suggests:
     rmarkdown,
     shiny (>= 1.6),
     testit,
-    tibble
+    tibble,
+    vctrs
 VignetteBuilder:
     knitr
 Encoding: UTF-8

NEWS.md

@@ -1,5 +1,7 @@
 # DT (development version)
 
+- Fix error rendering `vctrs::list_of` columns (#1180, @zeehio)
+
 # CHANGES IN DT VERSION 0.34
 
 - DT is now released under the MIT license (previously GPL-3) (#1175).

R/utils.R

@@ -44,6 +44,9 @@ captionString = function(caption) {
 boxAtomicScalarElements = function(x) {
   is_atomic = vapply(x, is.atomic, logical(1))
   if (all(is_atomic)) {
+    if (inherits(x, "vctrs_list_of")) {
+      x <- as.list(x)
+    }
     is_scalar = lengths(x) == 1L
     x[is_scalar] = lapply(x[is_scalar], list)
   }

tests/testit/test-utils.R

@@ -5,6 +5,19 @@ assert('dropNULL() works', {
   (dropNULL(list(a = 1, b = NULL)) %==% list(a = 1))
 })
 
+assert('boxAtomicScalarElements() works with vctrs::list_of lists', {
+  if (requireNamespace("vctrs", quietly = TRUE)) {
+    val1 <- list("a", c("a", "b"))
+    out1 <- boxAtomicScalarElements(val1)
+    val2 <- vctrs::as_list_of(val1)
+    out2 <- boxAtomicScalarElements(val2)
+    (out1 %==% out2)
+  } else {
+    message("test omitted: vctrs is not installed")
+    TRUE
+  }
+})
+
 assert('upperToDash() works', {
   (upperToDash('fontWeight') %==% 'font-weight')
   (upperToDash('backgroundColor') %==% 'background-color')