An extension of R's `help()` / `?` to work with roxygen style documentation written in a Pythonic / docstring style for non-packaged functions.

docstring.R

# An extension of help / `?` to work with roxygen documentation in a
# Pythonic / docstring style for non-packaged functions.


.fun_body = function(fun) {
  #' Get body of function (including comments) as a character vector
  #'
  #' @param fun name of function obj to return body of
  #'
  #' @return character vector of function body (1 element per line)
  #'
  #' @examples
  #' .fun_body(c)
  #' .fun_body(.fun_body)
  
  capture.output(
    print.function(fun, useSource = TRUE)
  )
}


.print_docstring = function(fun) {
  #' Show 'docstring' style documentation in function body
  #'
  #' @param fun function to search and print docstring for 
  #'
  #' @return NULL; output
  #' @export
  #'
  #' @examples
  #' .print_docstring(.print_docstring)
  
  doc_pattern = "^\\s+#'"
  fb = .fun_body(fun)
  doc_lines = fb[grep(doc_pattern, fb)]
  doc_lines = gsub(doc_pattern, "", doc_lines)
  
  print_doc = paste(doc_lines, collapse = "\n")
  cat(paste(print_doc, "\n"))
  invisible(print_doc)
}


help2 = function(topic, ...) {
  #' Extend help to try and print docstring style roxygen style docs in fun body
  #'
  #' @param topic name of topic/function to show help for
  #' @param ... additional params to be passed to help()
  #'
  #' @return NULL
  #'
  #' @examples
  #' help2(help2)
  #' help2(c)

  str_topic = as.character(substitute(topic))
  help_output = capture.output(help(str_topic, ...))

  if (length(help_output) != 0) {
    topic_obj = NULL
    try(expr = {
      topic_obj = get(str_topic)
    }, silent = TRUE)
    
    if (!is.null(topic_obj) & is.function(topic_obj)) {
      docs_out = .print_docstring(topic_obj)
      if (docs_out != "") return(invisible(NULL))
    }
  }

  cat(paste(help_output, collapse = "\n"))
  return(invisible(NULL))
}


`?` = help2