Add a "How to convert your Depends dependency on data.table to Imports" section to datatable-importing vignette?

[MichaelChirico]

#3076 was long ago but we keep seeing more and more packages with {data.table} in Depends ☹️

I started filing some PRs helping authors change to Imports, but it's hardly scalable:

• Switch data.table to Imports Brauckhoff/biopixR#5
• Switch data.table to Imports: entjos/TreeMineR#2
• Move data.table to Imports: immunomind/immunarch#404

Better might be a how-to guide in our docs somewhere. I'm only torn on whether this is better as an addition to the existing vignette, or a new Wiki page that can be more easily edited. Thoughts?

[Anirban166]

I think it would be valuable to have notes for that in both places. This fits in the subject matter of the importing vignette, and as you mentioned, a Wiki page would benefit from easy and instant updates by everyone (although I presume it may be less discoverable than a vignette).

[tdhock]

other packages are allowed to use Depends, if they want.
I don't think it is our respsonsibility to police Depends vs Imports usage. Do we gain something (less issues filed by users, etc?) by doing this policing?

[MichaelChirico]

#3076 cites the advantage to us being cleaning up this ugly code:

data.table/R/cedta.R

Line 64 in 898dce3

tryCatch("data.table" %chin% get(".Depends",paste("package",nsname,sep=":"),inherits=FALSE),error=function(e)FALSE) # both ns$.Depends and get(.Depends,ns) are not sufficient

but more broadly speaking, as an important package in the R ecosystem we can play a role in spreading awareness of best practices.

AFAICT 'Depends' is a relic of >10 years ago when that was the only way to do dependencies, but R can't remove it for back-compatibility.

I can also say that R at Google had an infrastructure issue where all Imports were converted to Depends and it caused absolute havoc. It took years to fix. From the experience of working on that I came away detesting Depends.

Anyway, while it's not a great use of dev time to go around fixing 90 other packages, we can offer a simple DIY guide like this and continued encouragement to drop Depends.