tweak c86424 for empty input

git-svn-id: https://svn.r-project.org/R/trunk@87831 00db46b3-68df-0310-9c12-caf00c1e9a41

Author: smeyer

src/library/base/R/version.R

@@ -1,7 +1,7 @@
 #  File src/library/base/R/version.R
 #  Part of the R package, https://www.R-project.org
 #
-#  Copyright (C) 1995-2024 The R Core Team
+#  Copyright (C) 1995-2025 The R Core Team
 #
 #  This program is free software; you can redistribute it and/or modify
 #  it under the terms of the GNU General Public License as published by
@@ -345,6 +345,8 @@ function(..., recursive = FALSE)
 duplicated.numeric_version <-
 function(x, incomparables = FALSE, ...)
 {
+    n <- length(x)
+    if (n < 2L) return(logical(n))
     x <- unclass(x)
     lens <- lengths(x, use.names = FALSE)
     need <- max(lens) - lens

tests/reg-tests-1e.R

@@ -1867,6 +1867,18 @@ stopifnot(exprs = {
 ## all these used to error in reformulate()  in R < 4.5.0
 
 
+## duplicated(<numeric_version>), especially for empty input
+options(warn = 2) # should already be set from the top
+x <- numeric_version("1")
+stopifnot(exprs = {
+    identical(duplicated(x[NULL]), logical(0L)) # should not warn
+    identical(duplicated(x), FALSE)
+    identical(duplicated(c(x,x)), c(FALSE, TRUE))
+})
+## only in R-devel with PR#18699, the first produced a warning
+## In max(lens) : no non-missing arguments to max; returning -Inf
+
+
 
 ## keep at end
 rbind(last =  proc.time() - .pt,