As an experimental feature the placeholder _ can now also be used in the ‘rhs’ of a forward pipe |> expression as the first argument in an extraction call, such as _$coef. More generally, it can be used as the head of a chain of extractions, such as _$coef[[2]].

R-devel/News, Mon, 13 Feb 2023

In upcoming versions of R, syntax such as the following will be supported:

as.data.table(mtcars) |> 
  _[am == 1] |> 
  _[, .(maxhp = max(hp)), by = .(cyl)]

#    cyl maxhp
# 1:   6   175
# 2:   4   113
# 3:   8   335

With this in mind, I think it's worth reconsidering whether DT() should remain on the release roadmap.

Some arguments in favor of scrapping DT() are as follows:

• Base R functionality dt |> _[...] will address all use cases for DT()
• Introducing an alternate syntax for calling [.data.table will be confusing for new users. Advertising this functionality also eliminates an opportunity to educate users about existing dt[...][...] chaining capabilities baked in by default
• Exporting DT() will lead to namespace collision issues with the DT::DT() exported by the widely used DT package
• DT() acceptance of non data.table objects is likely to cause user confusion
  • Unclear class for argument and return value of DT #5559
  • The new function DT() used for chaining/piping drops data.frame rownames names #5430
  • Naming conflict and unexpected behavior with the functional form of data.table DT() #5129
• Supporting DT() going forward will be a drain on valuable maintainer's time - DT() Labeled Issues
• DT() has not yet been exported in a CRAN release so no there will no impacts to reverse dependencies and limited impact to users who have adopted this form

That being said, this is just my two cents as a satisfied user of data.table interested in the long term success of the package. Happy to hear counter arguments, and open to the idea that the broader community may see enough value to finish the push to support DT().