From 431cca9cda350e5e4f7ab9ed2802a141a0013cb4 Mon Sep 17 00:00:00 2001
From: mikefc <coolbutuseless@users.noreply.github.com>
Date: Tue, 2 Apr 2024 00:58:39 +0000
Subject: [PATCH] Handle 'NA' in factors written as strings. [fixed #35]

---
 src/R-yyjson-serialize.c      |  2 ++
 tests/testthat/test-factors.R | 20 ++++++++++++++++++++
 2 files changed, 22 insertions(+)
 create mode 100644 tests/testthat/test-factors.R

diff --git a/src/R-yyjson-serialize.c b/src/R-yyjson-serialize.c
index e9fca3e..56795cd 100644
--- a/src/R-yyjson-serialize.c
+++ b/src/R-yyjson-serialize.c
@@ -261,6 +261,8 @@ yyjson_mut_val *scalar_factor_to_json_val(SEXP factor_, R_xlen_t idx,  yyjson_mu
   
   if (opt->factor == FACTOR_AS_INT) {
     val =  scalar_integer_to_json_val(factor, doc, opt);
+  } else if (factor == NA_INTEGER) {
+    val = yyjson_mut_null(doc);
   } else {
     SEXP nms_ = getAttrib(factor_, R_LevelsSymbol);
     const char *nm = CHAR(STRING_ELT(nms_, factor - 1));
diff --git a/tests/testthat/test-factors.R b/tests/testthat/test-factors.R
new file mode 100644
index 0000000..a68de19
--- /dev/null
+++ b/tests/testthat/test-factors.R
@@ -0,0 +1,20 @@
+
+test_that("multiplication works", {
+
+  # issue #35
+  color <- c("red", "blue", NA, "red", "white")
+  color <- factor(color, levels=c("red", "blue"))
+  color
+  
+  expect_no_error({
+    color_str <- yyjsonr::write_json_str(color, factor = 'integer')
+  })
+  expect_identical('[1,2,null,1,null]', color_str)
+  
+  expect_no_error({
+    color_str <- yyjsonr::write_json_str(color, factor = 'string')
+  })
+  expect_identical('["red","blue",null,"red",null]', color_str)
+
+})
+