If compatibility with versions older than 3.2 is important (debian 8.8 still only has 3.1) one might want to turn thedir.exists back intofile.exists instead.

Debian 8.8 is irrelevant as its sources for Rcpp match its sources for base R. Plus, we have the actively supported backport for R available via CRAN.

We could use thebackports package, or at least Suggests: it if we cared.

Team: Anybody see a problem depending on the now-two-year old R 3.2.0 ?

I'm guessing there are a lot of users in enterprise environments who are stuck with R 3.1.x or even R 3.0.x who would appreciate if we could remain compatible with R 3.0.0 and above, so I would be marginally in favor of just usingfile.exists() orutils::file_test("-d", ...) to be backwards compatible -- especially since the change is so small in this case.

Yes, that is a good policy. I can look into that while traveling the next two days. Of course I would be equally happy to receive a short PR :)

utils::file_test("-d", ...) is the perfect solution for this problem. Since I see no disadvantages in following that route, for simplicity, I've now hijacked my own pull request and turned it into this different solution for the same problem by force-pushing.

Yes, we have to remember that we bump our required version we implicitly bump the required version of 92% of CRAN (via recursive dependencies).