stop_input_type: Throw a type mismatch error

In rlang: Functions for Base Types and Core R and 'Tidyverse' Features

Throw a type mismatch error

Description

stop_input_type() throws an error when an argument has the wrong type, producing a friendly error message that includes the expected type and the actual type of the input.

Usage

stop_input_type(
  x,
  what,
  ...,
  allow_na = FALSE,
  allow_null = FALSE,
  show_value = TRUE,
  arg = caller_arg(x),
  call = caller_env()
)

Arguments

x	The object that does not conform to what. Its "friendly type" is used in the error message.
what	The friendly expected type as a string. Can be a character vector of expected types, in which case the error message mentions all of them in an "or" enumeration.
...	Additional arguments passed to abort().
allow_na	If TRUE, an NA description is appended to what in the error message.
allow_null	If TRUE, a NULL description is appended to what in the error message.
show_value	Whether to show the actual value in the error message.
arg	An argument name as a string. This argument will be mentioned in error messages as the input that is at the origin of a problem.
call	The execution environment of a currently running function, e.g. caller_env(). The function will be mentioned in error messages as the source of the error. See the call argument of abort() for more information.

Value

Throws an error, does not return.

See Also

Other input checkers: check_data_frame(), check_type_number, check_type_scalar

Examples

check_character <- function(
  x,
  ...,
  allow_null = FALSE,
  arg = caller_arg(x),
  call = caller_env()
) {
  if (!missing(x)) {
    if (is_character(x)) {
      return(invisible(NULL))
    }
    if (allow_null && is_null(x)) {
      return(invisible(NULL))
    }
  }

  stop_input_type(
    x,
    "a character vector",
    ...,
    allow_null = allow_null,
    arg = arg,
    call = call
  )
}

# Succeeds
check_character(letters)

# Fails
try(check_character(42))

rlang documentation built on April 6, 2026, 5:07 p.m.