Tools for input checking in functions

[Bisaloo]

This follows a discussion on our institute's slack workspace with @pearsonca, @seabbs, @TimTaylor.

What are the best practices for input checking in functions? This is an important question since R doesn't have an explicit type system (for now?).

• the base solution stop()/stopifnot(). stopifnot() can also take named argument to produce nicer error messages. It's also possible to write your own function if you end up testing the same kind of things many times.
• assertthat which seems to have been superseded by testthat (when used outside the testing framework)
• vctrs::vec_assert() which also works with data.frames
• checkmate
• check

check's README also mentions other alternatives that didn't come up in the discussion:

• https://bitbucket.org/richierocks/assertive
• https://docs.ropensci.org/assertr/
• https://github.com/smbache/ensurer

The popularity of each of these packages (as measured by the number of GitHub stars) makes a good case that such a blog post would be appreciated by the community 😄

[Bisaloo]

Also a good place to talk about https://github.com/ropensci-review-tools/autotest as a way to control you check your inputs correctly?

[maelle]

Oh yeah that's an excellent topic! Incidentally yesterday I was looking at the mlr dev docs and they mentioned checkmate.

Interested in contributing this post @Bisaloo et al?

[maelle]

Maybe relevant https://github.com/djnavarro/bs4cards/blob/master/R/validators.R

[TimTaylor]

Looks like rlang::abort() is having quite an update in the next version. Not sure when this is likely to land but currently it no longer hides the call by default. This has knock on effects with assertions in vctrs as they no longer hide the call by default in an RStudio session

library(vctrs)
f <- function(x) vec_assert(x, integer())
f(1)
#> Error in `vec_assert()`: `x` must be a vector with type <integer>.
#> Instead, it has type <double>.

Anyone have an idea of where they are in their release timeline so the post does not go out of date too quick? 😅
Edit - previous error would have been

#> Error: `x` must be a vector with type <integer>.
#> Instead, it has type <double>.

[Bisaloo]

Speaking of rlang, this might be relevant as well: r-lib/rlang#1111

[gaborcsardi]

FYI a new rlang release is in the works AFAIK.

[seabbs]

For reference: https://twitter.com/krlmlr/status/1449470169303195651?s=21