R/misc.R

In inbo/watina: Querying and Processing Data from the INBO Watina Database

#' Check availability of required packages
#'
#' Takes a vector of package names and passes each name to
#' \code{\link[base:ns-load]{requireNamespace()}};
#' if package(s) are missing, returns an error message providing the basic
#' \code{install.packages()} command to install them.
#'
#' @param pkgs A character vector of package names.
#'
#' @examples
#' \dontrun{
#' require_pkgs(c("a", "base", "b", "c"))
#' }
#'
#' @importFrom assertthat
#' assert_that
#' @keywords internal
require_pkgs <- function(pkgs) {
    assert_that(is.character(pkgs))
    available <- sapply(pkgs, requireNamespace, quietly = TRUE)
    if (!all(available)) {
        multiple <- sum(!available) > 1
        stop(ifelse(multiple, "Multiple", "A"),
             " package",
             ifelse(multiple, "s", ""),
             " needed for this function ",
             ifelse(multiple, "are", "is"),
             " missing.\nPlease install as follows: install.packages(",
             deparse(pkgs[!available]),
             ")",
             call. = FALSE)
    }
}