NULL needs one more layer of wrapping

Closes #203

NEWS.md

@@ -13,6 +13,8 @@ googlesheets4 now throws errors with class `"googlesheets4_error"` (#12).
 The `na` argument of `read_sheet()` has become more capable and more consistent with readr.
 Specifically, `na = character()` (or the general lack of `""` among the `na` strings) results in cells with no data appearing as the empty string `""` within a character vector, as opposed to `NA` (#174).
 
+Explicit `NULL`s are now written properly, i.e. as an empty cell (#203).
+
 ## Dependency changes
 
 * cli is new in Imports.

R/schema_CellData.R

@@ -56,7 +56,7 @@ cell_data <- function(x, val_type, .na = NULL) {
 
 #' @export
 as_CellData.NULL <- function(x, .na = NULL) {
-  empty_cell(.na)
+  list(empty_cell(.na))
 }
 
 #' @export

tests/testthat/test-range_write.R

@@ -41,6 +41,25 @@ test_that("range_write() works", {
   expect_equal(df, data[1:3])
 })
 
+# https://github.com/tidyverse/googlesheets4/issues/203
+test_that("we can write a hole-y tibble containing NULLs", {
+  skip_if_offline()
+  skip_if_no_token()
+
+  dat_write <- tibble::tibble(A = list(NULL, "HI"), B = month.abb[1:2])
+
+  ss <- local_ss(me_("write-NULL"), sheets = dat_write)
+  write_sheet(dat_write, ss, sheet = 1)
+
+  dat_read <- read_sheet(ss)
+  expect_equal(dat_read$A, c(NA, "HI"))
+  expect_equal(dat_read$B, dat_write$B)
+
+  dat_read <- read_sheet(ss, col_types = "Lc")
+  expect_equal(dat_read$A, dat_write$A)
+  expect_equal(dat_read$B, dat_write$B)
+})
+
 # ---- helpers ----
 test_that("prepare_loc() makes the right call re: `start` vs. `range`", {
   expect_loc <- function(x, loc) {

tests/testthat/test-schema_CellData.R

@@ -20,7 +20,7 @@ test_that("expect_empty_cell() is synced with empty_cell()", {
 })
 
 test_that("as_CellData() treats NULL as empty cell", {
-  expect_empty_cell(as_CellData(NULL))
+  expect_empty_cell(as_CellData(NULL)[[1]])
 })
 
 test_that("as_CellData() works for logical", {