Handle labelled values with no labels (#609)

Fixes #606

Author: jmobrien

NEWS.md

@@ -1,5 +1,8 @@
 # haven (development version)
 
+* `write_dta()` now correctly handles "labelled"-class numeric (double) variables 
+   that don't have value labels (@jmobrien, #606, #609).
+
 * `write_dta()` now allows variable names up to 32 characters (@sbae, #605).
 
 * Fix issue with `read_dta()` crashing R when StrL variables with missing values

R/haven-stata.R

@@ -139,6 +139,10 @@ validate_dta_label <- function(label) {
 # helpers -----------------------------------------------------------------
 
 has_non_integer_labels <- function(x) {
+  if (is.null(attr(x, "labels"))) {
+    return(FALSE)
+  }
+
   if (!is.labelled(x)) {
     return(FALSE)
   }

tests/testthat/test-haven-stata.R

@@ -164,6 +164,7 @@ test_that("can write labelled with NULL labels", {
   chr <- labelled(c("a", "b"), NULL)
 
   expect_equal(roundtrip_var(int, "dta"), c(1L, 2L))
+  expect_equal(roundtrip_var(num, "dta"), c(1L, 2L))
   expect_equal(roundtrip_var(chr, "dta"), c("a", "b"))
 })