Is Function Here — is_function

Check if required functions are present in installed packages. This controls the potential modifications of package contents.

Usage

is_function_here(fun, safer_check = TRUE, lib_path = NULL, error_text = "")

Arguments

fun: Character vector of the names of the required functions, preceded by the name of the package they belong to and a double or triple colon. Example: c("ggplot2::geom_point", "grid::gpar"). Warning: do not write "()" at the end of each tested function.
safer_check: Single logical value. Perform some "safer" checks? If TRUE, checkings are performed before main code running (see the safer-r project): 1) correct lib_path argument value 2) required functions and related packages effectively present in local R libraries and 3) R classical operators (like "<-") not overwritten by another package because of the R scope. Must be set to FALSE if this function is used inside another "safer" function to avoid pointless multiple checkings.
lib_path: Vector of characters specifying the absolute pathways of the directories containing the required packages for the function, if not in the default directories. Useful when R packages are not installed in the default directories because of lack of admin rights. More precisely, lib_path is passed through the new argument of .libPaths() so that the new library paths are unique(c(new, .Library.site, .Library)). Warning: .libPaths() is restored to the initial paths, after function execution. Ignored if NULL (default) or if the safer_check argument is FALSE: only the pathways specified by the current .libPaths() are used for package calling.
error_text: Single character string used to add information in error messages returned by the function, notably if the function is inside other functions, which is practical for debugging. Example: error_text = " INSIDE <PACKAGE_1>::<FUNCTION_1> INSIDE <PACKAGE_2>::<FUNCTION_2>.". If NULL, converted into "".

Value

An error message if at least one of the checked packages is missing in lib_path, or if at least one of the checked functions is missing in the required package, nothing otherwise.

Author

Gael Millot

Yushi Han

Haiding Wang

Examples

# Warning: these examples may not work well when using the "Run examples" link 
# because of a particular environment. Please, copy-paste in a local environment.
# See also https://safer-r.github.io/saferDev/articles/is_function_here.html
if (FALSE) {
# Example that returns an error
saferDev::is_function_here(fun = "ggplot2::notgood", error_text = " INSIDE P1::F1") # commented because this example returns an error
saferDev::is_function_here(fun = c("ggplot2::geom_point", "grid::gpar"))
saferDev::is_function_here(fun = "c")
}
saferDev::is_function_here(fun = "base::c", error_text = " INSIDE P1::F1")