Don't propagate NA language (#1395)

Fixes #1251

NEWS.md

@@ -1,5 +1,7 @@
 # roxygen2 (development version)
 
+* Generated HTML for code blocks never includes "NA" for language (#1251). 
+
 * Using a level 1 heading in the wrong tag now gives a more useful warning 
   (#1374).
 

R/markdown.R

@@ -150,8 +150,9 @@ eval_code_node <- function(node, env) {
     # write knitr markup for inline code
     text <- paste0("`", xml_text(node), "`")
   } else {
+    lang <- xml_attr(node, "info")
     # write knitr markup for fenced code
-    text <- paste0("```", xml_attr(node, "info"), "\n", xml_text(node), "```\n")
+    text <- paste0("```", if (!is.na(lang)) lang, "\n", xml_text(node), "```\n")
   }
   roxy_knit(text, env, knitr_chunk_defaults)
 }
@@ -315,8 +316,8 @@ special <- c(
 )
 
 mdxml_code_block <- function(xml, state) {
-  info <- xml_attr(xml, "info")[1]
-  if (is.na(info) || nchar(info[1]) == 0) info <- NA_character_
+  info <- xml_attr(xml, "info", default = "")[1]
+  if (nchar(info[1]) == 0) info <- NA_character_
   paste0(
     "\n\n",
     "\\if{html}{\\out{<div class=\"sourceCode",

tests/testthat/test-markdown-code.R

@@ -230,3 +230,16 @@ test_that("workaround for cmark sourcepos bug (#1353) works", {
   expect_equal(out$get_section("description")$value, "line1\npre 1 2 3 post")
   expect_equal(out$get_section("details")$value, "no workaround needed here")
 })
+
+
+test_that("doesn't generate NA language", {
+  out <- roc_proc_text(rd_roclet(), "
+  #' Title
+  #'
+  #' ```
+  #' r <- 1:10
+  #' ```
+  #' @md
+  foo <- function() {}")[[1]]
+  expect_false(grepl("NA", out$get_section("description")$value))
+})