tibble: A `tbl` may contain an external pointer via attribute `problems` set by readr about marshal HOT 4 OPEN

> x <- parse_integer(c("1X", "blah", "3"))
Warning: 2 parsing failures.
row col               expected actual
  1  -- no trailing characters   1X  
  2  -- no trailing characters   blah

> str(x)
 int [1:3] NA NA 3
 - attr(*, "problems")= tibble [2 × 4] (S3: tbl_df/tbl/data.frame)
  ..$ row     : int [1:2] 1 2
  ..$ col     : int [1:2] NA NA
  ..$ expected: chr [1:2] "no trailing characters" "no trailing characters"
  ..$ actual  : chr [1:2] "1X" "blah"

readr:::problems
function (x = .Last.value) 
{
    problems <- probs(x)
    if (is.null(problems)) {
        return(invisible(no_problems))
    }
    if (inherits(problems, "tbl_df")) {
        return(problems)
    }
    vroom::problems(x)
}

> vroom::problems
function (x = .Last.value, lazy = FALSE) 
{
    if (!inherits(x, "tbl_df")) {
        cli::cli_abort(c("The {.arg x} argument of {.fun vroom::problems} must be a data frame created by vroom:", 
            x = "{.arg x} has class {.cls {class(x)}}"))
    }
    if (!isTRUE(lazy)) {
        vroom_materialize(x, replace = FALSE)
    }
    probs <- attr(x, "problems")
    if (typeof(probs) != "externalptr") {
        cli::cli_abort(c("The {.arg x} argument of {.fun vroom::problems} must be a data frame created by vroom:", 
            x = "{.arg x} seems to have been created with something else, maybe readr?"))
    }
    probs <- vroom_errors_(probs)
    probs <- probs[!duplicated(probs), ]
    probs <- probs[order(probs$file, probs$row, probs$col), ]
    tibble::as_tibble(probs)
}
<environment: namespace:vroom>

prune.tbl_df <- function(x, ...) {
  problems <- attr(x, "problems", exact = TRUE)

  ## Materialize `problems` stored elsewhere in this process?
  if (typeof(problems) == "externalptr") {
     problems <- vroom::problems(x)
     attr(x, "problems") <- problems
  }

  x
}