R/reporter.r

In autodb: Automatic Database Normalisation for Data Frames

# utility function for printing optional progress messages without obfuscating
# program flow. op(eration) is designed to work in a pipe. exp(ression) is
# designed to work on a single statement, often an assignment. stat(ement) just
# prints the message if needed, and is otherwise a no-op.
reporter <- function(report, con, new = FALSE) {
  force(new)
  if (report)
    list(
      op = function(x, f, text, ...) {
        x <- eval(substitute(x, rlang::caller_env()))
        cat(paste0(text, "\n"), file = con, append = !new)
        utils::flush.console()
        new <<- FALSE
        f(x, ...)
      },
      exp = function(expression, text) {
        cat(paste0(text, "\n"), file = con, append = !new)
        utils::flush.console()
        new <<- FALSE
        eval(substitute(expression, rlang::caller_env()))
      },
      stat = function(text){
        cat(paste0(text, "\n"), file = con, append = !new)
        utils::flush.console()
        new <<- FALSE
        invisible(NULL)
      }
    )
  else
    list(
      op = function(x, f, text, ...) f(x, ...),
      exp = function(expression, text) {
        eval(substitute(expression, rlang::caller_env()))
      },
      stat = function(text) invisible(NULL)
    )
}