[R] Forward compatibility for dplyr::join_by() output

[nealrichardson]

Describe the enhancement requested

join_by(), a function coming in dplyr 1.1.0, returns a dplyr_join_by object: https://github.com/tidyverse/dplyr/blob/main/R/join-by.R#L274-L284

We should make sure we can map that output to the existing equality join arguments in case someone starts using it.

Component(s)

R

[r2evans]

@nealrichardson, are you planning to also support inequality comparisons?

[nealrichardson]

Acero (the C++ query engine in arrow) has some support for non-equality joins: residual predicates were added in #11579, and there is also an AsOfJoin node.

[paleolimbot]

I'm happy to review a PR for this although I will almost certainly not get to it before feature freeze on Monday!

[ianmcook]

I'll take a stab at this

[ianmcook]

#33664 adds support for join_by() with equality conditions. It does not add support for inequality conditions or the join helper functions that can were implemented in tidyverse/dplyr#5910.

Here's the GitHub issue for inequality joins: #29841

[r2evans]

Thanks! I look forward to 29841 as well!