preserve trailing blank line

Author: lorenzwalthert

NEWS.md

@@ -37,6 +37,7 @@
   detected (#881).
 * Add vignette on distributing style guide (#846, #861).
 * ensure a trailing blank line also if the input is cached (#867).
+* Preserve trailing blank line in roxygen examples (#880).
 * Fix argument name `filetype` in Example for `style_dir()` (#855).
 * An error is now thrown on styling if input unicode characters can't be 
   correctly parsed for Windows and R < 4.2 (#883).

R/roxygen-examples.R

@@ -102,6 +102,9 @@ style_roxygen_example_snippet <- function(code_snippet,
     mask <- decomposed$mask
   }
   code_snippet <- post_parse_roxygen(code_snippet)
+  append_empty <- !is_dont &&
+    length(code_snippet) > 1L &&
+    last(code_snippet) == ""
 
   cache_is_active <- cache_is_activated()
   is_cached <- is_cached(
@@ -116,10 +119,13 @@ style_roxygen_example_snippet <- function(code_snippet,
       parse_transform_serialize_r(transformers,
         base_indention = base_indention, warn_empty = FALSE
       )
-  } else {
-    code_snippet <- ensure_last_n_empty(code_snippet, n = 0)
   }
 
+  code_snippet <- ensure_last_n_empty(
+    code_snippet,
+    n = ifelse(append_empty, 1L, 0L)
+  )
+
   if (!is_cached && cache_is_active) {
     cache_write(
       code_snippet, transformers,

tests/testthat/roxygen-examples-complete/17-two-no-non-comment-out.R

@@ -4,6 +4,7 @@
 #' }
 #' # before this comment is a left-over space
 #' another_function <- function() NULL
+#'
 #' @examples
 #'   my_fun <- function() {
 #'   print("hello world!")

tests/testthat/roxygen-examples-complete/26-empty-trailing-lines-in.R

@@ -0,0 +1,30 @@
+#' this
+#'
+#' mey
+#' @examples
+#' 2 + 1
+#'
+NULL
+
+
+#' this
+#'
+#' mey
+#' @examples
+#' 2 + 1
+#'
+#'
+#'
+#'
+#'
+#'
+#'
+NULL
+
+
+#' this
+#'
+#' mey
+#' @examples
+#' 2 + 1
+NULL

tests/testthat/roxygen-examples-complete/26-empty-trailing-lines-in_tree

@@ -0,0 +1,24 @@
+#' this
+#'
+#' mey
+#' @examples
+#' 2 + 1
+#'
+NULL
+
+
+#' this
+#'
+#' mey
+#' @examples
+#' 2 + 1
+#'
+NULL
+
+
+#' this
+#'
+#' mey
+#' @examples
+#' 2 + 1
+NULL

tests/testthat/roxygen-examples-complete/26-empty-trailing-lines-out.R

@@ -131,4 +131,9 @@ test_that("analogous to test-roxygen-examples-complete", {
     "roxygen-examples-complete", "^25",
     transformer = style_text
   ), NA)
+
+  expect_warning(test_collection(
+    "roxygen-examples-complete", "^26",
+    transformer = style_text
+  ), NA)
 })