vetr: Verify Function Arguments Meet Structural Requirements

View source: R/validate.R

vetrR Documentation

Verify Function Arguments Meet Structural Requirements


Use vetting expressions to enforce structural requirements for function arguments. Works just like vet(), except that the formals of the enclosing function automatically matched to the vetting expressions provided in ....


vetr(..., .VETR_SETTINGS = NULL)



vetting expressions, each will be matched to the enclosing function formals as with and will be used to validate the value of the matching formal.


a settings list as produced by vetr_settings(), or NULL to use the default settings. Note that this means you cannot use vetr with a function that takes a .VETR_SETTINGS argument


Only named arguments may be vetted; in other words it is not possible to vet arguments passed via ....


TRUE if validation succeeds, otherwise stop with error message detailing nature of failure.

Vetting Expressions

Vetting expressions can be template tokens, standard tokens, or any combination of template and standard tokens combined with && and/or ||. Template tokens are R objects that define the required structure, much like the FUN.VALUE argument to vapply(). Standard tokens are tokens that contain the . symbol and are used to vet values.

If you do use the . symbol in your vetting expressions in your packages, you will need to include utils::globalVariables(".") as a top-level call to avoid the "no visible binding for global variable '.'"' R CMD check NOTE.

See vignette('vetr', package='vetr') and examples for details on how to craft vetting expressions.


vetr will force evaluation of any arguments that are being checked (you may omit arguments that should not be evaluate from vetr)

See Also

vet(), in particular example(vet).


fun1 <- function(x, y) {
  vetr(integer(), LGL.1)
  TRUE   # do some work
fun1(1:10, TRUE)
try(fun1(1:10, 1:10))

## only vet the second argument
fun2 <- function(x, y) {
  TRUE   # do some work
try(fun2(letters, 1:10))

## Nested templates; note, in packages you should consider
## defining templates outside of `vet` or `vetr` so that
## they are computed on load rather that at runtime
tpl <- list(numeric(1L), matrix(integer(), 3))
val.1 <- list(runif(1), rbind(1:10, 1:10, 1:10))
val.2 <- list(runif(1), cbind(1:10, 1:10, 1:10))
fun3 <- function(x, y) {
  vetr(x=tpl, y=tpl && ncol(.[[2]]) == ncol(x[[2]]))
  TRUE   # do some work
fun3(val.1, val.1)
try(fun3(val.1, val.2))
val.1.a <- val.1
val.1.a[[2]] <- val.1.a[[2]][, 1:8]
try(fun3(val.1, val.1.a))

vetr documentation built on Jan. 7, 2023, 1:19 a.m.