distinct() errors on missing columns

Fixes #4656

NEWS.md

@@ -6,6 +6,8 @@
   `eval_tbls2()` are now deprecated. That were only used in a handful of 
   packages, and we now believe that you're better off performing comparisons 
   more directly (#4675).
+* `distinct()` errors if you request it use variables that don't exist
+  (this was previously a warning) (#4656).
 
 * `tally()` and `count()` now error if the default output `name` (n), already
   exists in the data frame. You'll now need to specify it yourself; this 

R/distinct.R

@@ -78,33 +78,20 @@ distinct_prepare <- function(.data, vars, group_vars = character(), .keep_all =
   # Once we've done the mutate, we no longer need lazy objects, and
   # can instead just use their names
   missing_vars <- setdiff(distinct_vars, names(.data))
-
   if (length(missing_vars) > 0) {
-    missing_items <- fmt_items(fmt_obj(missing_vars))
-    distinct_vars <- distinct_vars[distinct_vars %in% names(.data)]
-    if (length(distinct_vars) > 0) {
-      true_vars <- glue("The following variables will be used:
-                        {fmt_items(distinct_vars)}")
-    } else {
-      true_vars <- "The operation will return the input unchanged."
-    }
-    msg <- glue("Trying to compute distinct() for variables not found in the data:
-                {missing_items}
-                This is an error, but only a warning is raised for compatibility reasons.
-                {true_vars}
-                ")
-    warn(msg)
+    abort(c(
+      "distinct() must use existing variables",
+      glue("`{missing_vars}` not found in `.data`")
+    ))
   }
 
-  new_vars <- unique(c(distinct_vars, group_vars))
-
-  # Keep the order of the variables
-  out_vars <- intersect(names(.data), new_vars)
+  # Always include grouping variables preserving input order
+  out_vars <- intersect(names(.data), c(distinct_vars, group_vars))
 
   if (.keep_all) {
     keep <- seq_along(.data)
   } else {
-    keep <- unique(out_vars)
+    keep <- out_vars
   }
 
   list(data = .data, vars = out_vars, keep = keep)

tests/testthat/test-distinct-error.txt

@@ -0,0 +1,13 @@
+> df %>% distinct(aa, x)
+Error: distinct() must use existing variables
+* `aa` not found in `.data`
+
+> df %>% distinct(aa, bb)
+Error: distinct() must use existing variables
+* `aa` not found in `.data`
+* `bb` not found in `.data`
+
+> df %>% distinct(.data$aa)
+Error: distinct() must use existing variables
+* `aa` not found in `.data`
+

tests/testthat/test-distinct.R

@@ -70,63 +70,11 @@ test_that("empty grouped distinct equivalent to empty ungrouped", {
 test_that("distinct gives a warning when selecting an unknown column (#3140)", {
   df <- tibble(g = c(1, 2), x = c(1, 2))
 
-  expect_warning(
-    distinct(df, aa),
-    glue("Trying to compute distinct() for variables not found in the data:
-         - `aa`
-         This is an error, but only a warning is raised for compatibility reasons.
-         The operation will return the input unchanged."),
-    fixed = TRUE
-  )
-  expect_warning(
-    distinct(df, .data$aa),
-    glue("Trying to compute distinct() for variables not found in the data:
-      - `aa`
-      This is an error, but only a warning is raised for compatibility reasons.
-      The operation will return the input unchanged."),
-    fixed = TRUE
-    )
-
-
-  expect_warning(
-    distinct(df, aa, x),
-    glue("Trying to compute distinct() for variables not found in the data:
-         - `aa`
-         This is an error, but only a warning is raised for compatibility reasons.
-         The following variables will be used:
-         - x"),
-    fixed = TRUE
-  )
-  expect_warning(
-    distinct(df, .data$aa, x),
-    glue("Trying to compute distinct() for variables not found in the data:
-      - `aa`
-      This is an error, but only a warning is raised for compatibility reasons.
-      The following variables will be used:
-      - x"),
-    fixed = TRUE
-    )
-
-  expect_warning(
-    distinct(df, g, aa, x),
-    glue("Trying to compute distinct() for variables not found in the data:
-         - `aa`
-         This is an error, but only a warning is raised for compatibility reasons.
-         The following variables will be used:
-         - g
-         - x"),
-    fixed = TRUE
-  )
-  expect_warning(
-    distinct(df, g, .data$aa, x),
-    glue("Trying to compute distinct() for variables not found in the data:
-      - `aa`
-      This is an error, but only a warning is raised for compatibility reasons.
-      The following variables will be used:
-      - g
-      - x"),
-    fixed = TRUE
-    )
+  verify_output(test_path("test-distinct-error.txt"), {
+    df %>% distinct(aa, x)
+    df %>% distinct(aa, bb)
+    df %>% distinct(.data$aa)
+  })
 })
 
 test_that("distinct on a new, mutated variable is equivalent to mutate followed by distinct", {