fix: handle NA values in separate_longer_position() (#1625)

- Preserve NA rows in output instead of erroring with 'to' must be a finite number
- Handle all-NA and mixed empty/NA edge cases
- Add tests for NA handling consistency with separate_longer_delim()

Author: LeonidasZhak

R/separate-longer.R

@@ -77,11 +77,31 @@ str_split_length <- function(x, width = 1) {
     return(list())
   }
 
+  na <- is.na(x)
+  if (all(na)) {
+    return(rep(list(NA_character_), length(x)))
+  }
+  if (any(na)) {
+    x <- x[!na]
+  }
+
   max_length <- max(stringr::str_length(x))
-  idx <- seq(1, max_length, by = width)
 
-  pieces <- stringr::str_sub_all(x, cbind(idx, length = width))
-  pieces <- map(pieces, function(x) x[x != ""])
+  if (max_length == 0L) {
+    pieces <- map(x, function(x) character())
+  } else {
+    idx <- seq(1, max_length, by = width)
+    pieces <- stringr::str_sub_all(x, cbind(idx, length = width))
+    pieces <- map(pieces, function(x) x[x != ""])
+  }
+
+  if (any(na)) {
+    pieces_na <- vector("list", length(na))
+    pieces_na[!na] <- pieces
+    pieces_na[na] <- rep(list(NA_character_), sum(na))
+    pieces <- pieces_na
+  }
+
   pieces
 }
 

tests/testthat/test-separate-longer.R

@@ -39,6 +39,20 @@ test_that("works with zero-row data frame", {
   expect_equal(separate_longer_delim(df, x, ","), df)
 })
 
+test_that("separate_longer_position() handles NA values (#1625)", {
+  df <- tibble(id = 1:3, x = c("abcd", NA, "ef"))
+  out <- separate_longer_position(df, x, width = 2)
+  expect_equal(out$id, c(1, 1, 2, 3))
+  expect_equal(out$x, c("ab", "cd", NA, "ef"))
+})
+
+test_that("separate_longer_position() handles all-NA input", {
+  df <- tibble(id = 1:2, x = c(NA, NA))
+  out <- separate_longer_position(df, x, width = 1)
+  expect_equal(out$id, c(1, 2))
+  expect_equal(out$x, c(NA_character_, NA_character_))
+})
+
 test_that("separate_longer_position() validates its inputs", {
   df <- tibble(x = "x")
   expect_snapshot(error = TRUE, {