R/list_files.R

In arnaudgallou/toolkit: Helpers Functions

#' @title List files in a directory
#' @description A wrapper around [`list.files()`] that gives the possibility to name each file directly.
#' @param path A character vector of full path names.
#' @param target An optional [`regular expression`][regex()] to return only file names that match the regular expression.
#' @param names A vector of names to assign to each file, a function, formula or regular expression to extract names from file names.
#' @param full.names Should the full path be returned?
#' @param ... Other arguments passed on to [`list.files()`].
#' @param err_on_empty If `TRUE`, the function throws an error if no files are matched.
#' @return A character vector of class `collection`.
#' @export
list_files <- function(path = ".", target = NULL, names, full.names = TRUE, ..., err_on_empty = TRUE) {
  if (!missing(names) && !(is.function(names) || is_formula(names) || is.character(names))) {
    stop("'names' must be a function, formula, character vector or string.")
  }

  out <- list.files(path, target, full.names = full.names, ...)

  if (isTRUE(err_on_empty) && is_empty(out)) {
    stop("targeted files could not be found.")
  }

  if (!missing(names)) {
    if (is.function(names) || is_formula(names)) {
      nm <- as_function(names)(out)
    } else if (is.string(names) && has_metachr(names)) {
      nm <- string_extract(basename(out), names)
    } else {
      nm <- names
    }

    out <- setNames(out, nm)
  }

  structure(out, class = c("collection", "character"))
}


#' @export
print.collection <- function(x, ...) {
  print(x[seq_along(x)], ...)
}


#' @title Extract file names
#' @description Extract the file name from a full path name.
#' @param path A character vector of path names.
#' @param to_snake_case Should the file name be converted to snake case?
#' @export
extract_file_name <- function(path, to_snake_case = FALSE) {
  file_name <- basename(tools::file_path_sans_ext(path))
  if (isTRUE(to_snake_case)) {
    file_name <- to_snake_case(file_name)
  }
  file_name
}