fix names_sd rev dep issue 6033 (#6238)

* fix names_sd rev dev issue 6033

* Simplify test and improve comment about version

* remove trailing ws

* revdev->revdep

---------

Co-authored-by: Benjamin Schwendinger <benjaminschwe@gmail.com>
Co-authored-by: Michael Chirico <michaelchirico4@gmail.com>
Co-authored-by: Michael Chirico <chiricom@google.com>

R/data.table.R

@@ -1121,6 +1121,11 @@ replace_dot_alias = function(e) {
           if (is.name(lhs)) {
             lhs = as.character(lhs)
           } else {
+            #6033 revdep. Slowly deprecate in 1.17.0. Caller has given us `dt[, substitute(names(.SD))]` which means
+            # jsub is actually substitute(names(.SD)) instead of just names(.SD)
+            if (lhs %iscall% 'substitute')
+              lhs = eval(lhs, parent.frame(), parent.frame())
+
             # lhs is e.g. (MyVar) or get("MyVar") or names(.SD) || setdiff(names(.SD), cols)
             lhs = eval(lhs, list(.SD = setNames(logical(length(sdvars)), sdvars)), parent.frame())
           }

inst/tests/tests.Rraw

@@ -18383,10 +18383,13 @@ test(2250.11, dt[, names(.SD(2)) := lapply(.SD, .I)], error=base_messages$missin
 dt = data.table(a = 1:3, b = 5:7, grp = c('a', 'a', 'b'))
 test(2250.12, dt[, names(.SD) := lapply(.SD, function(x) x + b), .SDcols = "a"], data.table(a = 1:3 + 5:7, b = 5:7, grp = c('a', 'a', 'b')))
 
-
 dt = data.table(a = 1L, b = 2L, c = 3L, d = 4L, e = 5L, f = 6L)
 test(2250.13, dt[, names(.SD)[1:5] := sum(.SD)], data.table(a = 21L, b = 21L, c = 21L, d = 21L, e = 21L, f = 6L))
 
+dt = data.table(a = 1) #6033 revdep follow-up
+my_col = "a"
+test(2250.14, dt[, substitute(my_col) := .(3)], data.table(a = 3))
+
 # fread(...,fill) can also be used to specify a guess on the maximum number of columns #2691 #1812 #4130 #3436 #2727
 dt_str = paste(rep(c("1,2\n", "1,2,3\n"), each=100), collapse="")
 ans = data.table(1L, 2L, rep(c(NA, 3L), each=100L))