Use is_unspecified() in vec_cast.list.default()

R/type-bare.R

@@ -413,12 +413,14 @@ vec_cast.list.list <- function(x, to, ...) {
 #' @export
 #' @method vec_cast.list default
 vec_cast.list.default <- function(x, to, ...) {
-  if (inherits(x, "vctrs_unspecified")) {
+  if (is_unspecified(x)) {
     return(vec_init(to, length(x)))
   }
 
   out <- lapply(seq_along(x), function(i) x[[i]])
 
+  vec_slice(out, vec_equal_na(x)) <- list(NULL)
+
   if (!is.object(to)) {
     out <- shape_broadcast(out, to)
   }
@@ -433,6 +435,13 @@ vec_cast.list.data.frame <- function(x, to, ...) {
   # equivalent for `vec_get()`
   row.names(x) <- NULL
   out <- vec_chop(x)
+
+  vec_slice(out, vec_equal_na(x)) <- list(NULL)
+
+  if (!is.object(to)) {
+    out <- shape_broadcast(out, to)
+  }
+
   out
 }
 

tests/testthat/test-type-bare.R

@@ -302,7 +302,7 @@ test_that("can sort raw", {
 
 test_that("safe casts work as expected", {
   expect_equal(vec_cast(NULL, list()), NULL)
-  expect_equal(vec_cast(NA, list()), list(NA))
+  expect_equal(vec_cast(NA, list()), list(NULL))
   expect_equal(vec_cast(1:2, list()), list(1L, 2L))
   expect_equal(vec_cast(list(1L, 2L), list()), list(1L, 2L))
 })
@@ -320,6 +320,28 @@ test_that("data frames are cast to list row wise (#639)", {
   expect_equal(vec_cast(x, list()), expect)
 })
 
+test_that("data frames can be cast to shaped lists", {
+  to <- array(list(), dim = c(0, 2, 1))
+  x <- data.frame(x = 1:2, y = 3:4)
+
+  expect <- list(vec_slice(x, 1), vec_slice(x, 2))
+  expect <- array(expect, dim = c(2, 2, 1))
+
+  expect_equal(vec_cast(x, to), expect)
+})
+
+test_that("Casting atomic `NA` values to list results in a `NULL`", {
+  x <- c(NA, 1)
+  expect <- list(NULL, 1)
+  expect_equal(vec_cast(x, list()), expect)
+})
+
+test_that("Casting data frame `NA` rows to list results in a `NULL`", {
+  x <- data.frame(x = c(NA, NA, 1), y = c(NA, 1, 2))
+  expect <- list(NULL, vec_slice(x, 2), vec_slice(x, 3))
+  expect_equal(vec_cast(x, list()), expect)
+})
+
 # Unspecified
 
 test_that("unspecified can be cast to bare methods", {