R/check-library-function.R

In Data-Camp/testwhat: Easily write submission correctness tests for R exercises

#' Check whether the library function was called correctly
#' 
#' Convenience function to test in a very hacky way whether 
#' the library function was called correctly in its most simple form.
#' There is support for the different ways to call the library function
#' 
#' @param state state to start from
#' @param package package name for which the library()
#' function should've been called
#' @param not_called_msg optional feedback message in case the library
#' function wasn't called a single time
#' @param incorrect_msg optional feedback message in case the library
#' function wasn't called for the specified package.
#' @inheritParams test_function
#' 
#' @examples
#' \dontrun{
#' # example solution
#' library(ggvis)
#' 
#' # sct to test whether ggvis was loaded
#' ex() %>% check_library("ggvis")
#' }
#' 
#' @export
check_library <- function(state, package, not_called_msg = NULL, incorrect_msg = NULL) {
  assert_state(state)
  if(is.null(not_called_msg)) {
    not_called_msg <- sprintf("Make sure to call the `library()` function to load the `%s` package.", package)
  }
  
  if(is.null(incorrect_msg)) {
    incorrect_msg <- sprintf("Have you correctly called the `library()` function to load the `%s` package?", package)
  }
  
  state %>% check_code(regex = "(library|require)\\(", missing_msg = not_called_msg,
                       append = is.null(not_called_msg), drop_comments = TRUE)
  state %>% check_code(regex = sprintf("(library|require)\\s*\\(\\s*[\"']?%s[\"']?\\s*\\)",package),
                       missing_msg = incorrect_msg, append = is.null(incorrect_msg), drop_comments = TRUE)
  return(state)
}

test_library_function <- function(package,
                          not_called_msg = NULL, 
                          incorrect_msg = NULL) {
  fail_if_v2_only()
  ex() %>% check_library(package, not_called_msg = not_called_msg, incorrect_msg = incorrect_msg)
}