Allow setDT(get(...)) to work as previously

Author: MichaelChirico

R/data.table.R

@@ -2987,6 +2987,11 @@ setDT = function(x, keep.rownames=FALSE, key=NULL, check.names=FALSE) {
     } else if (isS4(k)) {
       .Call(CsetS4elt, k, as.character(name[[3L]]), x)
     }
+  } else if (name %iscall% "get") { # #6725
+    name = match.call(get, name)
+    name[[1L]] = quote(assign)
+    name$value = quote(x)
+    eval(name)
   }
   .Call(CexpandAltRep, x)  # issue#2866 and PR#2882
   invisible(x)

inst/tests/tests.Rraw

@@ -20653,6 +20653,14 @@ setDT(d2)
 test(2295.1, !is.data.table(d1))
 test(2295.2, rownames(d1), 'b')
 test(2295.3, is.data.table(d2))
+# Ensure against regression noted in #6725
+x = data.frame(a=1)
+e = environment()
+foo = function() {
+  setDT(get('x', envir=e))
+}
+foo()
+test(2295.4, is.data.table(x))
 
 # #6588: .checkTypos used to give arbitrary strings to stopf as the first argument
 test(2296, d2[x %no such operator% 1], error = '%no such operator%')