error on duplicated names

R/select_nse.R

@@ -89,6 +89,14 @@
       # after inclusion and exclusion, the original values in "select"
       # may have changed, so we check that we only add names of valid values
       out <- stats::setNames(out, names(new_names)[new_names %in% out])
+      # check if we have any duplicated names, and if so, give an error
+      if (anyDuplicated(names(out)) > 0) {
+        insight::format_error(paste0(
+          "Following names were duplicated after renaming: ",
+          text_concatenate(names(out)[duplicated(names(out))], enclose = "`"),
+          ". Using duplicated names is no good practice and therefore discouraged. Please provide unique names."
+        ))
+      }
     }
   }
 

tests/testthat/test-data_select.R

@@ -427,4 +427,13 @@ test_that("data_select renames variables on the fly", {
     data_select(mtcars, c(new = "mpg", "cyl", hoho = "wt"), exclude = "wt"),
     c("new", "cyl")
   )
+  # error when names are not unique
+  expect_error(
+    data_select(mtcars, c(new = "mpg", old = "cyl", new = "wt")), # nolint
+    regex = "Following names were duplicated"
+  )
+  expect_error(
+    data_select(mtcars, c(new = "mpg", "cyl", cyl = "wt")), # nolint
+    regex = "Following names were duplicated"
+  )
 })