R/execute_script.R

In ucbds-infra/ottr: An R Autograding Extension for Otter-Grader

#' Generate an environment from an R script
#'
#' @description Execute a string as an R script and return the environment from that execution.
#'
#' Converts a string to an AST and executes that script in a dummy environment for running test
#' cases against. Transforms all expressions of the form `. = ottr::check(...)` by replacing the `.`
#' with an index into a list in the environment with name `check_results_{SECRET}` to collect the
#' [TestFileResult] objects generated from those checks. (This helps to handle variable
#' name collisions in tests when grading a script.)
#'
#' @param script The string to be executed
#' @param ignore_errors Whether to ignore errors thrown while executing the script
#'
#' @return The global environment after executing the script
execute_script <- function(script, ignore_errors) {
  if (missing(ignore_errors)) {
    ignore_errors <- TRUE
  }

  # convert script to a list of expressions
  tree <- as.list(parse(text = script))

  #  create dummy env for execution
  test_env <- new.env()

  # run the script, capturing stdout, and return the environment
  testthat::capture_output({
    for (expr in tree) {
      tryCatch(
        eval(expr, envir = test_env),
        error = function(e) {
          if (!ignore_errors) {
            stop(e)
          }
        }
      )
    }
  }, print = TRUE)
  return(test_env)
}