chk is an R package for developers to check user-supplied function arguments. It is designed to be simple, customizable and fast.
chk_ functions check the properties of individual objects. For example
chk_flag(x) checks whether
x is a flag, i.e., a non-missing logical vector of length 1.
chk_ functions are called for their side-effects, i.e., they throw an informative error if the object fails the check.
The error messages, which follow the tidyverse style guide, are designed to allow the user to quickly identify the problem with the argument value(s) they are providing. The errors are rlang errors of subclass
chk_ function has a matching
vld_ function which returns a flag indicating whether the object passed the check.
vld_ functions allow developers to provide their own error messages.
chk_ functions are designed to be used within functions. Consequently, when constructing an error message they use the name of the object that they received as this is expected to be the name of the argument.
If this is not the case, developers can provide a different name using the
vld_) functions are not expected to be directly exposed to users they don’t check any of their arguments (other than the object of interest of course!) to ensure that they are as fast as possible.
chk_flag() function illustrates the general structure of a
chk_ function initially checks the object (using its
vld_ partner) and if the object passes the check immediately returns an invisible
NULL. If, and only if, the object fails the check does the
chk_ function construct and then throw an informative error message.
abort_chk() functions are exported to make it easy for programmers to develop their own
chk_ functions. The chk-lgl.R script illustrates the general template to use when developing your own
abort_chk() function converts multiple arguments to a string using
paste0(..., collapse = '') and provides number sensitive
sprintf-like types. By default it also capitalizes the first character and adds a missing period.
check_ functions are more complex then the
chk_ functions which make them slower but makes doing some general tests easier. These functions are used to check the parameters of the object.