closes #406

Author: topepo

R/fit.R

@@ -100,6 +100,9 @@ fit.model_spec <-
     if (object$mode == "unknown") {
       rlang::abort("Please set the mode in the model specification.")
     }
+    if (!identical(class(control), class(control_parsnip()))) {
+      rlang::abort("The 'control' argument should have class 'control_parsnip'.")
+    }
     dots <- quos(...)
     if (is.null(object$engine)) {
       eng_vals <- possible_engines(object)
@@ -189,6 +192,9 @@ fit_xy.model_spec <-
            control = control_parsnip(),
            ...
   ) {
+    if (!identical(class(control), class(control_parsnip()))) {
+      rlang::abort("The 'control' argument should have class 'control_parsnip'.")
+    }
     object <- check_mode(object, levels(y))
     dots <- quos(...)
     if (is.null(object$engine)) {

tests/testthat/test_misc.R

@@ -85,8 +85,22 @@ test_that('S3 method dispatch/registration', {
   )
   expect_true(tibble::is_tibble(res))
 
+})
 
+# ------------------------------------------------------------------------------
 
+test_that('control class', {
+  x <- linear_reg() %>% set_engine("lm")
+  ctrl <- control_parsnip()
+  class(ctrl) <- c("potato", "chair")
+  expect_error(
+    fit(x, mpg ~ ., data = mtcars, control = ctrl),
+    "The 'control' argument should have class 'control_parsnip'"
+  )
+  expect_error(
+    fit_xy(x, x = mtcars[, -1], y = mtcars$mpg, control = ctrl),
+    "The 'control' argument should have class 'control_parsnip'"
+  )
 })