Make read_line more robust in conjunction with skip_blank_rows

Fixes #968

NEWS.md

@@ -9,6 +9,8 @@
 
 ## Additional features and fixes
 
+* `read_lines(skip_empty_rows = TRUE)` no longer crashes if a file ends with an empty line (#968)
+
 * `write_*()` functions gain a `eol =` argument to control the end of line character used (#857). This allows writing of CSV files with Windows newlines (CRLF) if desired.
 
 * `write_excel_csv()` no longer outputs a byte order mark when appending to a file (#1075).

src/TokenizerLine.h

@@ -39,7 +39,7 @@ class TokenizerLine : public Tokenizer {
     if (!moreTokens_)
       return Token(TOKEN_EOF, line_, 0);
 
-    while (cur_ != end_) {
+    while (cur_ < end_) {
       Advance advance(&cur_);
 
       if (*cur_ == '\0')

tests/testthat/test-read-lines.R

@@ -59,6 +59,17 @@ test_that("allocation works as expected", {
   expect_equal(length(read_lines(tmp)), 2^11)
 })
 
+test_that("read_lines(skip_empty_rows) works when blank lines are at the end of the file (#968)", {
+  tmp <- tempfile()
+  on.exit(unlink(tmp))
+
+  writeLines(con = tmp,
+"test
+")
+
+  expect_equal(read_lines(tmp, skip_empty_rows = TRUE), "test")
+})
+
 # These tests are slow so are commented out
 #test_that("long vectors are supported", {
   #tmp <- tempfile(fileext = ".gz")