Dependency on R >= 4.0

[shikokuchuo]

Just curious as to the reason such a recent version is required. I'm also not aware of many features introduced by that version!

nanonext/mirai only require R >= 3.5 to ensure R serialization version 3 is present - so that all clients are interoperable. There is also a use of ...length() in mirai although this could trivially be avoided if necessary.

[wlandau]

I don't remember. I may have wanted to use tools::R_user_dir() at some point, but that must have been a long time ago. Regardless, I think R 4.0.0 is old enough for this restriction to be harmless. Not sure what kind of Chesterton fence I would hit by decreasing the minimum version.

[shikokuchuo]

OK. Just wanted to point out that mirai/nanonext don't have such requirements and (at least theoretically) there could be targets users that are prevented from using crew.

[wlandau]

You bring up a good point. However, requiring 4.0.0 seems unlikely to cause problems in practice, and I don't have time to retest on 3.x.x. If 4.0.0 is too strict at the moment, it seems like a problem that will solve itself over time.