How can I combine errors?

Question

It's frustrating to have to fix issues one by one when the code had all the info to give exhaustive help from the first run.

and1 <- function(a , b) {
  stopifnot(is.logical(a), is.logical(b))
  a & b
}

and1(0, 1)     # nope
#> Error in and1(1, 2): is.logical(a) is not TRUE

# fix it
and1(FALSE, 1) # still not good
#> Error in and1(FALSE, 2): is.logical(b) is not TRUE

# fix again
and1(FALSE, TRUE) # finally works
#> [1] FALSE

We can design complex combination but this looks bad and with more checks it would become very complicated very fast.

and2 <- function(a , b) {
  if (!is.logical(a)) {
    if (!is.logical(b)) {
      stop("\n`a` must be logical\n`b` must be logical")
    }
    stop("`a` must be logical")
  }
  if (!is.logical(b)) {
    stop("`b` must be logical")
  }
  stopifnot(is.logical(a), is.logical(b))
  a & b
}

and2(1,2)
#> Error in and2(1, 2): 
#> `a` must be logical
#> `b` must be logical

What's a good way to do this without the messy code ?

Answer 1

I'd probably make a named logical vector and then check that vector

and1 <- function(a,b){
  
  checks <- c(
    "`a` must be logical" = !is.logical(a),
    "`b` must be logical" = !is.logical(b)
  )
  
  if(any(checks)) {
    paste("\n",names(checks[which(checks)]), collapse = "") |> 
      stop()
  }

  a & b
}

and1(1,2)
#> Error in and1(1, 2) : 
#> `a` must be logical
#> `b` must be logical

(format the error message as desired)