data.table breaks xts first(), last() distpatching

[ethanbsmith]

upgrading to data.table 12.6 breaks existing xts first(), last() dispatching. Im not sure what the last working verison was, but the broke somewhere between 12.2 and 12.6. reverting to 12.2 restores expected behavior

library(quantmod)
r <- getSymbols("SPY", auto.assign=F)
> last(r)
           SPY.Open SPY.High SPY.Low SPY.Close SPY.Volume SPY.Adjusted
2019-11-15   311.02   311.84  310.26    311.79   62023600       311.79
> library(data.table)
> last(r)
[1] 311.79

[jangorecki]

I am pretty sure it is my fault, made in #3859
I knew it might be breaking change thus asked for revdeps check, but it appears none of the revdeps was testing that. Thanks for reporting.
fyi @joshuaulrich

[joshuaulrich]

Thanks @jangorecki! Let me know if there's anything I can do in xts to help catch things like this in the future, and/or I can do anything to help our two packages play nicely together.

[jangorecki]

@joshuaulrich extra eyes on a fix PR would be helpful. Thanks

[joshuaulrich]

Hi Jan, I looked at the PR, and I don't have a good enough understanding of the underlying code to make useful comments.