From 1faa87328e30bc2bced0edcf30c2adf332ee8ea0 Mon Sep 17 00:00:00 2001
From: Dmitry Shemetov <dshemetov@ucdavis.edu>
Date: Sat, 24 Feb 2024 10:32:02 -0800
Subject: [PATCH] fix: mutable dt alias from unique.data.table #5932 Thanks to
 @brookslogan for the original bug report.

---
 R/duplicated.R | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/R/duplicated.R b/R/duplicated.R
index 901d6e3c0..7fc7124a7 100644
--- a/R/duplicated.R
+++ b/R/duplicated.R
@@ -28,7 +28,7 @@ unique.data.table = function(x, incomparables=FALSE, fromLast=FALSE, by=seq_alon
   if (!isFALSE(incomparables)) {
     .NotYetUsed("incomparables != FALSE")
   }
-  if (nrow(x) <= 1L) return(x)
+  if (nrow(x) <= 1L) return(copy(x))
   if (!length(by)) by = NULL  #4594
   o = forderv(x, by=by, sort=FALSE, retGrp=TRUE)
   if (!is.null(cols)) {