Get (recursive) package dependencies

package_dependencies.R

library(stringr)
package_names_from_description <- function(pkg, imports=TRUE){
  # include imports as well as depends
  deps <- c("Depends",if(imports)"Imports")
  pkg_descr <- packageDescription(pkg,fields=deps)
  pkg_list <- unlist(pkg_descr)
  pkg_list <- pkg_list[!is.na(pkg_list)]
  if (length(pkg_list)==0)return(character(0))
  pkg_full_names <- unlist(str_split(as.character(pkg_list),","))
  # Strip the version info from the name
  pkg_info <- str_match(str_trim(pkg_full_names),
                        "^([a-zA-Z0-9]+)([[:space:]]+\\(>=[[:space:]]+[0-9.-]*\\))?$")
  # Only return the package names
  pkg_names <- pkg_info[,2]
  pkg_names[!is.na(pkg_names)]
}

#' Get recursive package dependencies
#' 
#' Checks the package description and recursively adds identified dependencies until
#' no new dependencies are found.
#' 
#' @param pkg character value name(s) of package(s) to search through
#' @param imports whether to include packages under \code{Imports} as dependencies
#' @param recursive whether to include indirect/recursive dependencies as well as immediate dependencies
#' @param exclude character vector containing any package to exclude from the dependencies
#' 
package_dependencies <- function(pkg, imports=TRUE, recursive=TRUE,
                                 exclude=c("R",getOption("defaultPackages"))){
  all_pkgs <- c(exclude)
  pkgs_to_check <- c(pkg)
  while(length(pkgs_to_check)){
    # Pop the next package off the list
    pkg <- pkgs_to_check[1]
    pkgs_to_check <- pkgs_to_check[-1]
    pkg_deps <- package_names_from_description(pkg,imports=imports)
    new_pkgs <- setdiff(pkg_deps, all_pkgs)
    all_pkgs <- c(all_pkgs, new_pkgs)
    # Push all new dependencies to the list of packages to check
    # (if recursive)
    if (recursive) pkgs_to_check <- c(pkgs_to_check, new_pkgs)
  }
  setdiff(all_pkgs,exclude)
}