R/replace_null_fn.R

In MiguelRodo/gamlsspipeline:

#' @title Replace NULL functions
#'
#' @description
#' Replaces functions that are NULL or missing in a specified environment with functions whose body is \code{NULL; NULL} and
#' have empty arguments as specified.
#'
#' @param env environment. Environment in which the functions are to be found and replaced.
#' @param expected_params named list. Names are names of functions in \code{env} and values
#' are character vectors specifying parameters for functions.
#'
#' @examples
#' env_curr <- environment()
#' fn1 <- function(x) x; fn2 <- function(x = 2) y; fn3 <- NULL
#' expected_params <- list(fn1 = 'x', fn2 = 'y', fn3 = 'x')
#' .replace_null_fns(env = env_curr, expected_params = expected_params)
#' fn3 # replaced to have a function with arguments as specified by expected_params
#' fn2; fn1 # no change in either
.replace_null_fns <- function(env, expected_params){
  purrr::walk(names(expected_params), function(fn_name) .replace_null_fn(fn_name = fn_name, env = env,
                                                                         expected_params = expected_params[[fn_name]]))
  invisible(TRUE)
}

#' @title Replace NULL function of a given name
.replace_null_fn <- function(fn_name, env, expected_params){
  # get function from environment
  fn <- env[[fn_name]]

  # return fn if it's not NULL
  if(!is.null(fn)) return(invisible(TRUE))

  # create base function
  if(fn_name == 'preprocess_fn'){
    fn <- function(){
      NULL
      data_raw
    }
  } else{
    fn <- function(){
      NULL
      NULL
    }
  }

  # change parameters of function to what's required
  formals(fn) <- purrr::map(seq_along(expected_params), function(x) NULL) %>%
    setNames(expected_params)

  # assign function to environment
  assign(x = fn_name, value = fn, envir = env)

  # output
  invisible(TRUE)
}