verify n arg of dbFetch

Author: jimhester

NEWS.md

@@ -12,6 +12,7 @@
   This avoids problems with drivers that don't support batch sizes larger than the input size.
   To restore the behavior prior to this release pass `batch_rows = 1024` or set `options(odbc.batch_rows = 1024)` (#391).
 * `dbBind()` and `dbFetch()` now support multiple result sets (@vkapartzianis, #234)
+* `dbFetch()` now verifies that `n` is a valid input.
 
 # odbc 1.2.3
 

R/Result.R

@@ -55,6 +55,7 @@ setMethod(
 setMethod(
   "dbFetch", "OdbcResult",
   function(res, n = -1, ...) {
+    n <- check_n(n)
     result_fetch(res@ptr, n)
   })
 

R/utils.R

@@ -58,3 +58,11 @@ id_field <- function(id, field, default = NULL) {
     default
   }
 }
+
+check_n <- function(n) {
+  if (length(n) != 1) stop("`n` must be scalar", call. = FALSE)
+  if (n < -1) stopc("`n` must be nonnegative or -1")
+  if (is.infinite(n)) n <- -1
+  if (trunc(n) != n) stopc("`n` must be a whole number", call. = FALSE)
+  n
+}