So the other day I was wondering how I could determine the minimum R version I technically need to depend on in my R package, tadaatoolbox. Naturally, I asked #rstats, and I got a neat suggestion which I implemented hastily like this:

library(stringr)
library(purrr)
library(desc)
library(dplyr)

# Get vector of package dependencies
deps <- tools::package_dependencies("tadaatoolbox")[[1]]
# Remove base packages
deps <- deps[!(deps %in% getOption("defaultPackages"))]

deptbl <- map_df(deps, function(x) {
  # Parse package DESCRIPTION file
  descr   <- system.file("DESCRIPTION", package = x)
  # Get the "Depends" field
  depends <- desc_get("Depends", descr)[[1]]

  # Return a data.drame
  data.frame(package = x,
             depends = depends,
             stringsAsFactors = FALSE
  )
})

# Extract R version number, sort, print
deptbl %>%
  mutate(depends = str_extract(depends, "(\\d+\\.)?(\\d+\\.)?(\\*|\\d+)")) %>%
  arrange(desc(depends)) %>%
  knitr::kable()
package depends
DescTools 3.3.1
car 3.2.0
pixiedust 3.1.2
ggplot2 3.1
viridis 2.10
broom NA
magrittr NA
pwr NA
nortest NA

So, now I have a neat little table.
Couple things to note:

Current R-devel doesn’t like you to depend on an R version with a non-zero patch-level, i.e. you should depend on R (>= 3.2.0) rather than R (>= 3.2.1).
So even if I want to be safe and depend on the highest dependency in the list (DescTools with R (>= 3.3.1)), I can only really depend on R (>= 3.3.0) and wait for DescTools to comply with the new rules.
The next thing that irks me is that DescTools has such a high dependency, and I couldn’t find out why that has to be or if the devs were just taking the easy route on that one. Since I can’t find the package on GitHub, I guess I won’t be able to easily find that out since I can’t file an issue anywhere.

Lastly, I was surprised that packages like broom or nortest don’t even explicitly depend on any specific R version, I did not know that’s an option. Or if it was an option, I would have assumed it’s discouraged.

So maybe my desire do “depend properly” is totally meaningless anyway and I just should let it go.
So that’s what I’ll do for now.

EDIT:

You might also be interested in this discussion on about whether or not this is a good approach, and what else you might want to do to ensure you depend meaningfully.