[R-pkg-devel] Testing on old R versions

[Duncan Murdoch]

I just received a bug report about the rgl package:  it claims to depend 
on R >= 3.2.0, but actually uses the hcl.colors() function that was 
introduced in R 3.6.0, so fails to install.  (This dependence was 
introduced while I had the dependence stated as R >= 4.0.0 for a while, 
until I tried to help people stuck on old releases; I fixed some of the 
4.0.0 needs, but missed this one.)

So of course what I should have done was to run the checks on R 3.2.0 
(and maybe intermediate versions) to confirm it works, but I didn't try 
that before releasing to CRAN.

I've just finished installing a copy of R 3.2.0 and testing my fix, so I 
think things are fine now.  This took some work; some of the packages 
used by the current rgl didn't exist when R 3.2.0 was current, so no 
binaries exist for them; installing the tools for binary builds takes 
time, etc.

So finally, my question:  what is the recommended way to handle tests of 
new packages on old R versions?  Do docker or other images exist that 
are already set up and ready to go?

Duncan Murdoch