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Assert Argument is an Expression

Source: R/assertions.R
assert_expr.Rd

Assert Argument is an Expression

Usage

assert_expr(
  arg,
  optional = FALSE,
  arg_name = gsub("^enexpr\\((.*)\\)$", "\\1", rlang::caller_arg(arg)),
  message = NULL,
  class = "assert_expr",
  call = parent.frame()
)

Arguments

arg

A function argument to be checked

Default value

none

optional

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

Default value

FALSE

arg_name

By default the expression specified for arg is used. If it is of the form enexpr(<argument name>), the enexpr() part is removed. For example if arg = enexpr(filter_add) is specified, arg_name defaults to "filter_add"

Default value

gsub("^enexpr\((.*)\)$", "\1", rlang::caller_arg(arg))

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.

Default value

NULL

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 an expression, i.e. either a symbol or a call, or returns the input invisibly otherwise

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_list(), 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()