skip_if_not_r_version()?

[MichaelChirico]

This is #773 reborn, in a way.

Yes, skip_if_not(getRversion() >= "4.2.0") is pretty straightforward if you know about getRversion() and that there's a coercion method for strings that makes this work (quite infamously recently we found many people doing getRversion() >= 4.2 & subsequently booted from CRAN 😄).

But empirically, I have seen many different versions of equivalent skips. I think it's a common enough reason to skip tests that it warrants inclusion (alongside the similar skip_if_not_installed()). I have also seen a few packages implement similar helpers; centralizing that logic in {testthat} also makes sense to me. E.g. here's {lintr}'s version:

https://github.com/r-lib/lintr/blob/4de229f55e9387379beb42f61c235266bbc68dcd/tests/testthat/helper.R#L55-L59

Here are some other similar helpers:

https://github.com/cran/prt/blob/42ab58a2e712350735bd9eb54c6ff092e3192356/tests/testthat/helper-functions.R#L17-L21
https://github.com/cran/duckdb/blob/8bd532e6576edb85df225f3b7335ef90c17e92d0/tests/testthat/test-backend-dbplyr__duckdb_connection.R#L1-L5

Here are hits for a few iterations of ways this is done:

• "canonical-ish": 218 hits. Using getRversion(). But also notice hits like skip_if(grepl("...", getRversion())): https://github.com/search?q=org%3Acran%20path%3Atestthat%20%2Fskip.*getRversion%2F&type=code
• Messing around with R.version(). Messy. 42 hits. https://github.com/search?q=org%3Acran+path%3Atestthat+%2Fskip.*R%5C.Version%2F&type=code
• skip_if_not_installed() on a default package, e.g. skip_if_not_installed("base", "4.0.0"): 42 hits. Esoteric. https://github.com/search?q=org%3Acran+path%3Atestthat+%2Fskip_if_not_installed%5C%28%5Cs*%5B%22%27%5D%28base%7Cutils%7Ctools%7Cstats%7Cgraphics%7CgrDevices%7Cdatasets%7Cmethods%29%2F&type=code

Even allowing that using getRversion() is common enough & the "correct" way, a dedicated skip_if_not_r_version() also allows making a neater message in the test logs.

c.f.

testthat::skip_if_not(getRversion() >= '6.6.6')
# Error: Reason: getRversion() >= "6.6.6" is not TRUE

lintr::skip_if_not_r_version('6.6.6')
# Error: Reason: R version at least 6.6.6 is required