Fix parsing of NaN and Inf to only be that exact strings, rather than…

… extensions

We don't want to parse NaNa, Inform or Info as doubles

Fixes tidyverse/readr#1319

NEWS.md

@@ -1,5 +1,8 @@
 # vroom (development version)
 
+* Values with only a `Inf` or `NaN` prefix but additional data afterwards, like
+  `Inform` or no longer inappropriately guessed as doubles (https://github.com/tidyverse/readr/issues/1319)
+
 * Time types now support `%h` format to denote hour durations greater than 24, like readr (https://github.com/tidyverse/readr/issues/1312)
 
 * Fix performance issue when materializing subsetted vectors (#378)

src/vroom_dbl.cc

@@ -84,12 +84,12 @@ double bsd_strtod(const char* begin, const char* end, const char decimalMark) {
     ++p;
 
   /* NaN */
-  if (end - p >= 3 && tolower(p[0]) == 'n' && tolower(p[1]) == 'a' &&
+  if (end - p == 3 && tolower(p[0]) == 'n' && tolower(p[1]) == 'a' &&
       tolower(p[2]) == 'n') {
     return NAN;
   }
   /* Inf */
-  if (end - p >= 3 && tolower(p[0]) == 'i' && tolower(p[1]) == 'n' &&
+  if (end - p == 3 && tolower(p[0]) == 'i' && tolower(p[1]) == 'n' &&
       tolower(p[2]) == 'f') {
     return sign == 1 ? -HUGE_VAL : HUGE_VAL;
   }

tests/testthat/test-dbl.R

@@ -25,7 +25,17 @@ test_that("NaN values are guessed and parsed as doubles (https://github.com/tidy
     equals = tibble::tibble(x = c(NaN)))
 })
 
+test_that("Test that values with only a NaN prefix are _not_ parsed as doubles", {
+  test_vroom(I("x\nNaNa\n"), delim = ",", col_types = "?",
+    equals = tibble::tibble(x = c("NaNa")))
+})
+
 test_that("Inf and -Inf values are guessed and parsed as doubles (https://github.com/tidyverse/readr/issues/1283)", {
   test_vroom(I("x\nInf\n-Inf\n+Inf"), delim = ",", col_types = "?",
     equals = tibble::tibble(x = c(Inf, -Inf, Inf)))
 })
+
+test_that("Test that values with only a Inf prefix are _not_ parsed as doubles", {
+  test_vroom(I("x\nInfa\n-Infb\n+Infc"), delim = ",", col_types = "?",
+    equals = tibble::tibble(x = c("Infa", "-Infb", "+Infc")))
+})