assert_function_expects_n_arguments {assertions}

Assert function expects n arguments

Description

Assert a function expects n arguments, with user control over how variable arguments (...) are counted (default throws error)

Usage

assert_function_expects_n_arguments(
  x,
  n,
  dots = c("throw_error", "count_as_0", "count_as_1", "count_as_inf"),
  msg = NULL,
  call = rlang::caller_env(),
  arg_name = NULL
)

Arguments

x

a function to check has exactly N arguments

n

number of arguments that must be expected by function to pass assertion (integer)

dots

how to deal with '...' dots (a.k.a variable arguments). Should we count as 0, 1 or infinite arguments. Or, do we just throw an error when we see '...' (default)

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 expects exactly n arguments, otherwise aborts with the error message specified by msg