improve error when outcome is missing (#1016)

NEWS.md

@@ -1,5 +1,7 @@
 # parsnip (development version)
 
+* Improved errors in cases where the outcome column is mis-specified. (#1003)
+
 # parsnip 1.1.1
 
 * Fixed bug where prediction on rank deficient `lm()` models produced `.pred_res` instead of `.pred`. (#985)

R/misc.R

@@ -354,6 +354,16 @@ check_outcome <- function(y, spec) {
     return(invisible(NULL))
   }
 
+  has_no_outcome <- if (is.atomic(y)) {is.null(y)} else {length(y) == 0}
+  if (isTRUE(has_no_outcome)) {
+    cli::cli_abort(
+      c("!" = "{.fun {class(spec)[1]}} was unable to find an outcome.",
+        "i" = "Ensure that you have specified an outcome column and that it \\
+               hasn't been removed in pre-processing."),
+      call = NULL
+    )
+  }
+
   if (spec$mode == "regression") {
     outcome_is_numeric <- if (is.atomic(y)) {is.numeric(y)} else {all(map_lgl(y, is.numeric))}
     if (!outcome_is_numeric) {

tests/testthat/_snaps/misc.md

@@ -140,6 +140,33 @@
       Error in `check_outcome()`:
       ! For a regression model, the outcome should be `numeric`, not a `factor`.
 
+---
+
+    Code
+      check_outcome(NULL, reg_spec)
+    Condition
+      Error:
+      ! `linear_reg()` was unable to find an outcome.
+      i Ensure that you have specified an outcome column and that it hasn't been removed in pre-processing.
+
+---
+
+    Code
+      check_outcome(tibble::new_tibble(list(), nrow = 10), reg_spec)
+    Condition
+      Error:
+      ! `linear_reg()` was unable to find an outcome.
+      i Ensure that you have specified an outcome column and that it hasn't been removed in pre-processing.
+
+---
+
+    Code
+      fit(reg_spec, ~mpg, mtcars)
+    Condition
+      Error:
+      ! `linear_reg()` was unable to find an outcome.
+      i Ensure that you have specified an outcome column and that it hasn't been removed in pre-processing.
+
 ---
 
     Code
@@ -148,6 +175,33 @@
       Error in `check_outcome()`:
       ! For a classification model, the outcome should be a `factor`, not a `integer`.
 
+---
+
+    Code
+      check_outcome(NULL, class_spec)
+    Condition
+      Error:
+      ! `logistic_reg()` was unable to find an outcome.
+      i Ensure that you have specified an outcome column and that it hasn't been removed in pre-processing.
+
+---
+
+    Code
+      check_outcome(tibble::new_tibble(list(), nrow = 10), class_spec)
+    Condition
+      Error:
+      ! `logistic_reg()` was unable to find an outcome.
+      i Ensure that you have specified an outcome column and that it hasn't been removed in pre-processing.
+
+---
+
+    Code
+      fit(class_spec, ~mpg, mtcars)
+    Condition
+      Error:
+      ! `logistic_reg()` was unable to find an outcome.
+      i Ensure that you have specified an outcome column and that it hasn't been removed in pre-processing.
+
 ---
 
     Code

tests/testthat/test_misc.R

@@ -205,6 +205,21 @@ test_that('check_outcome works as expected', {
     check_outcome(factor(1:2), reg_spec)
   )
 
+  expect_snapshot(
+    error = TRUE,
+    check_outcome(NULL, reg_spec)
+  )
+
+  expect_snapshot(
+    error = TRUE,
+    check_outcome(tibble::new_tibble(list(), nrow = 10), reg_spec)
+  )
+
+  expect_snapshot(
+    error = TRUE,
+    fit(reg_spec, ~ mpg, mtcars)
+  )
+
   class_spec <- logistic_reg()
 
   expect_no_error(
@@ -220,6 +235,21 @@ test_that('check_outcome works as expected', {
     check_outcome(1:2, class_spec)
   )
 
+  expect_snapshot(
+    error = TRUE,
+    check_outcome(NULL, class_spec)
+  )
+
+  expect_snapshot(
+    error = TRUE,
+    check_outcome(tibble::new_tibble(list(), nrow = 10), class_spec)
+  )
+
+  expect_snapshot(
+    error = TRUE,
+    fit(class_spec, ~ mpg, mtcars)
+  )
+
   # Fake specification to avoid having to load {censored}
   cens_spec <- logistic_reg()
   cens_spec$mode <- "censored regression"