R/knitrRule.R

In beerda/rmake: Makefile Generator for R Analytical Projects

#' Rule for building text documents by using the knitr package
#'
#' This rule is for execution of knitr in order to create the text file,
#' as described in [knitr:knit()].
#'
#' This rule executes the following command in a separate R process:
#' `library(knitr); params <- params; knitr::knit(script, output=target)`
#'
#' That is, parameters given in the `params` argument are stored into the global variable
#' and then the `script` is processed with knitr. That is, the re-generation of the
#' `Makefile` with any change to `params` will not cause the re-execution of the recipe unless
#' any other script dependencies change.
#'
#' Issuing `make clean` from the shell causes removal of all files specified in `target` parameter.
#'
#' @param target Name of the output file to be created
#' @param script Name of the RNW file to be rendered
#' @param depends A vector of file names that the markdown script depends on, or `NULL`.
#' @param params A list of R values that become available within the `script` in
#' a `params` variable.
#' @param task A character vector of parent task names. The mechanism of tasks allows to
#' group rules. Anything different from `'all'` will
#' cause creation of a new task depending on the given rule. Executing `make taskname`
#' will then force building of this rule.
#' @return Instance of S3 class `rmake.rule`
#' @seealso [markdownRule()], [rule()], [makefile()], [rRule()]
#' @author Michal Burda
#' @examples
#' r <- knitrRule(target='report.tex',
#'                script='report.Rnw',
#'                depends=c('data1.csv', 'data2.csv'))
#'
#' # generate the content of a makefile (as character vector)
#' makefile(list(r))
#'
#' # generate to file
#' tmp <- tempdir()
#' makefile(list(r), file.path(tmp, "Makefile"))
#' @export
#' @importFrom knitr knit
knitrRule <- function(target,
                      script,
                      depends=NULL,
                      params=list(),
                      task='all') {
  assert_that(is.character(target))
  assert_that(is.string(script))
  assert_that(is.null(depends) || is.character(depends))
  assert_that(is.list(params))
  assert_that(is.character(task))

  allDeps <- c(script, depends)

  p <- c(list(.target=target,
              .script=script,
              .depends=depends,
              .task=task),
         params)
  rm(params)

  rule(target=target,
       depends=allDeps,
       build=inShell({
         library(knitr)
         params <- p
         knitr::knit(script, output=target)
       }),
       clean=paste0('$(RM) ', paste0(sanitizePath(target), collapse=' ')),
       task=task,
       type='knitr')
}