preserve other classes when using setDT

[mpavlis]

When I import a shapefile using the function st_read from the library sf I get an object of class sf and data.frame.

library(sf) 
 
library(data.table)  

polygon_data <- st_read("my_data.shp")

If I then use the function setDT to coerce it to data.table, the sf class is not preserved. Could it be possible for setDT to preserve other classes than data.frame when coercing an object?

[arunsrinivasan]

This was the functionality before.. until #1078 and #1128 were reported.

I'm not so much in favour of adding an argument for this. Not sure what others think.