Assert function expects specific parameter names — assert_function

Assert that a function signature includes required set of parameter names in its formal argument list, regardless of whether those parameters have default values. The ... argument is ignored.

Usage

assert_function_expects(
  x,
  required,
  msg = NULL,
  call = rlang::caller_env(),
  arg_name = NULL
)

Arguments

x: a function to check for required parameter names
required: a character vector of parameter names that must appear in the function signature (order does not matter)
msg: The error message thrown if the assertion fails (string)
call: Only relevant when pooling assertions into multi-assertion helper functions. See cli_abort for details.
arg_name: Advanced use only. Name of the argument passed (default: NULL, will automatically extract arg_name).

Value

invisible(TRUE) if function x declares all required parameters, otherwise aborts with the error message specified by msg

Examples

my_fun <- function(x, y = 1, ...) x + y
assert_function_expects(my_fun, c("x", "y"))

try({
  assert_function_expects(my_fun, c("x", "z"))
})
#> Error in eval(expr, envir) : 
#>   Function 'my_fun' is missing the following parameter in its signature:
#> `z`