R/package.r

In hadley/packman:

#' Description object (S3): creation, coercion and testing.
#' 
#' This object represents a package \code{DESCRIPTION} file.
#' 
#' @param ... fields that become components of the package. These are currently
#'   not verified in any way.
#' @export
#' @examples
#' package_info(base(), "MASS")
#' package_info(test_source(), "ggplot2")
description <- function(...) {
  obj <- list(...)
  obj$.sources <- parse_spec(obj$Sources)
  obj$.dependencies <- parse_all_deps(obj)
    
  structure(obj, class = "description")
}

#' @S3method print description
print.description <- function(x, ...) {
  cat("<Package> ", x$Package, "\n", sep = "")
  
  deps <- x$.dependencies
  if (!is.null(deps)) {
    deps_string <- paste0("Deps: ", paste0(deps$name, 
                          " (", tolower(substr(deps$field, 1, 1)), ")", 
                          collapse = ", "))
    cat(strwrap(deps_string, exdent = 2), sep = "\n")
  }
  
  print(x$source)
}

#' @export
#' @rdname description
is.description <- function(x) inherits(x, "description")

#' @param x
#' @param source the data source from which the package came
#' @export 
#' @rdname description
as.description <- function(x, source) {
  assert_that(is.source(source))
  UseMethod("as.description")
}

#' @S3method as.description character
as.description.character <- function(x, source) {
  assert_that(length(x) == 1)
  
  as.description(textConnection(x), source)
}

#' @S3method as.description connection
as.description.connection <- function(x, source) {
  already_open <- isOpen(x)
  if (!already_open) on.exit(close(x))
  
  dcf <- read.dcf(x)
  obj <- as.list(as.data.frame(dcf, stringsAsFactors = FALSE))
  as.description(obj, source)
}

#' @S3method as.description data.frame
as.description.data.frame <- function(x, source) {
  as.description(as.list(x), source)
}

#' @S3method as.description list
as.description.list <- function(x, source) {
  x$source <- source
  
  do.call("description", x)
}

#' @S3method install description
install.description <- function(source, package, library, ...) {
  install(package$source, package, library, ...)
}