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Is an Argument a List of Expressions?

Source: R/assertions.R
assert_expr_list.Rd

Checks if the argument is a list of expressions.

Usage

assert_expr_list(
  arg,
  required_elements = NULL,
  named = FALSE,
  optional = FALSE,
  arg_name = rlang::caller_arg(arg),
  message = NULL,
  class = "assert_expr_list",
  call = parent.frame()
)

Arguments

arg

A function argument to be checked

required_elements

A character vector of names that must be present in arg

named

If set to TRUE, an error is issued if not all elements of the list are named.

optional

Is the checked argument optional? If set to FALSE and arg is NULL then an error is thrown.

arg_name

string indicating the label/symbol of the object being checked.

message

string passed to cli::cli_abort(message). When NULL, default messaging is used (see examples for default messages). "{arg_name}" can be used in messaging.

class

Subclass of the condition.

call

The execution environment of a currently running function, e.g. call = caller_env(). The corresponding function call is retrieved and mentioned in error messages as the source of the error.

You only need to supply call when throwing a condition from a helper function which wouldn't be relevant to mention in the message.

Can also be NULL or a defused function call to respectively not display any call or hard-code a code to display.

For more information about error calls, see Including function calls in error messages.

Value

The function throws an error if arg is not a list of expressions. Otherwise, the input it returned invisibly.

See also

Checks for valid input and returns warning or errors messages: assert_atomic_vector(), assert_character_scalar(), assert_character_vector(), assert_data_frame(), assert_date_vector(), assert_expr(), assert_filter_cond(), assert_function(), assert_integer_scalar(), assert_list_element(), assert_list_of(), assert_logical_scalar(), assert_named(), assert_numeric_vector(), assert_one_to_one(), assert_param_does_not_exist(), assert_s3_class(), assert_same_type(), assert_symbol(), assert_unit(), assert_vars(), assert_varval_list()

Examples

library(rlang)

example_fun <- function(vars) {
  assert_expr_list(vars)
}
example_fun(exprs(DTHDOM = "AE", DTHSEQ = AESEQ))

try(example_fun(exprs("AE", DTSEQ = AESEQ, !!list("a"), !!list("a"))))
#> Error in example_fun(exprs("AE", DTSEQ = AESEQ, !!list("a"), !!list("a"))) : 
#>   All elements of `vars` must be an expression.
#> ℹ `vars[[3]]` = `list("a")` is of type <list>, and `vars[[4]]` = `list("a")` is
#>   of type <list>