Fail on NULL engine

NEWS.md

@@ -47,6 +47,8 @@
 
 * The quantile regression prediction type was disabled for the deprecated `surv_reg()` model. 
 
+* `NULL` is no longer accepted as an engine (#1242).
+
 
 # parsnip 1.2.1
 

R/engines.R

@@ -111,7 +111,7 @@ set_engine <- function(object, engine, ...) {
 set_engine.model_spec <- function(object, engine, ...) {
   mod_type <- class(object)[1]
 
-  if (rlang::is_missing(engine)) {
+  if (rlang::is_missing(engine) | is.null(engine)) {
     stop_missing_engine(mod_type, call = caller_env(0))
   }
   object$engine <- engine

tests/testthat/_snaps/args_and_modes.md

@@ -108,16 +108,16 @@
     Code
       linear_reg() %>% set_engine()
     Condition
-      Error in `set_engine()`:
-      ! Missing engine. Possible mode/engine combinations are: quantile regression {quantreg} and regression {lm, glm, glmnet, stan, spark, keras, brulee}.
+      Error in `set_engine.model_spec()`:
+      ! argument "engine" is missing, with no default
 
 ---
 
     Code
       proportional_hazards() %>% set_engine()
     Condition
-      Error in `set_engine()`:
-      ! No known engines for `proportional_hazards()`.
+      Error in `set_engine.model_spec()`:
+      ! argument "engine" is missing, with no default
 
 # set_* functions error when input isn't model_spec
 

tests/testthat/_snaps/engines.md

@@ -0,0 +1,8 @@
+# NULL engines
+
+    Code
+      set_engine(nearest_neighbor(), NULL)
+    Condition
+      Error in `set_engine()`:
+      ! Missing engine. Possible mode/engine combinations are: classification {kknn} and regression {kknn}.
+

tests/testthat/_snaps/mars.md

@@ -19,8 +19,8 @@
     Code
       translate(mars(mode = "regression") %>% set_engine())
     Condition
-      Error in `set_engine()`:
-      ! Missing engine. Possible mode/engine combinations are: classification {earth} and regression {earth}.
+      Error in `set_engine.model_spec()`:
+      ! argument "engine" is missing, with no default
 
 ---
 

tests/testthat/_snaps/multinom_reg.md

@@ -37,8 +37,8 @@
     Code
       multinom_reg(penalty = 0.1) %>% set_engine()
     Condition
-      Error in `set_engine()`:
-      ! Missing engine. Possible mode/engine combinations are: classification {glmnet, spark, keras, nnet, brulee}.
+      Error in `set_engine.model_spec()`:
+      ! argument "engine" is missing, with no default
 
 # check_args() works
 

tests/testthat/_snaps/nullmodel.md

@@ -3,8 +3,8 @@
     Code
       translate(null_model(mode = "regression") %>% set_engine())
     Condition
-      Error in `set_engine()`:
-      ! Missing engine. Possible mode/engine combinations are: classification {parsnip} and regression {parsnip}.
+      Error in `set_engine.model_spec()`:
+      ! argument "engine" is missing, with no default
 
 ---
 

tests/testthat/_snaps/rand_forest.md

@@ -19,8 +19,9 @@
 
     Code
       res <- translate(rand_forest(mode = "classification") %>% set_engine(NULL))
-    Message
-      Used `engine = 'ranger'` for translation.
+    Condition
+      Error in `set_engine()`:
+      ! Missing engine. Possible mode/engine combinations are: classification {ranger, randomForest, spark} and regression {ranger, randomForest, spark}.
 
 ---
 

tests/testthat/_snaps/surv_reg.md

@@ -32,8 +32,9 @@
 
     Code
       res <- translate(surv_reg() %>% set_engine(NULL))
-    Message
-      Used `engine = 'survival'` for translation.
+    Condition
+      Error in `set_engine()`:
+      ! Missing engine. Possible mode/engine combinations are: regression {flexsurv, survival}.
 
 # deprecation warning
 

tests/testthat/_snaps/svm_linear.md

@@ -20,8 +20,8 @@
     Code
       translate(svm_linear(mode = "regression") %>% set_engine(NULL))
     Condition
-      Error in `translate.default()`:
-      ! Please set an engine.
+      Error in `set_engine()`:
+      ! Missing engine. Possible mode/engine combinations are: classification {LiblineaR, kernlab} and regression {LiblineaR, kernlab}.
 
 ---
 

tests/testthat/_snaps/svm_poly.md

@@ -28,6 +28,6 @@
     Code
       svm_poly() %>% set_engine(NULL) %>% translate()
     Condition
-      Error in `translate.default()`:
-      ! Please set an engine.
+      Error in `set_engine()`:
+      ! Missing engine. Possible mode/engine combinations are: classification {kernlab} and regression {kernlab}.
 

tests/testthat/_snaps/svm_rbf.md

@@ -48,6 +48,6 @@
     Code
       translate(svm_rbf(mode = "regression") %>% set_engine(NULL))
     Condition
-      Error in `translate.default()`:
-      ! Please set an engine.
+      Error in `set_engine()`:
+      ! Missing engine. Possible mode/engine combinations are: classification {kernlab, liquidSVM} and regression {kernlab, liquidSVM}.
 

tests/testthat/test-engines.R

@@ -0,0 +1,8 @@
+test_that("NULL engines", {
+  # See issue https://github.com/tidymodels/parsnip/issues/1242
+
+  expect_snapshot(
+    set_engine(nearest_neighbor(), NULL),
+    error = TRUE
+  )
+})

tests/testthat/test-rand_forest.R

@@ -8,7 +8,10 @@ test_that('updating', {
 })
 
 test_that('bad input', {
-  expect_snapshot(res <- translate(rand_forest(mode = "classification") %>% set_engine(NULL)))
+  expect_snapshot(res <-
+                    translate(rand_forest(mode = "classification") %>%
+                                set_engine(NULL)),
+                  error = TRUE)
   expect_snapshot(error = TRUE, rand_forest(mode = "time series"))
   expect_snapshot(error = TRUE, translate(rand_forest(mode = "classification") %>% set_engine("wat?")))
 })

tests/testthat/test-surv_reg.R

@@ -13,7 +13,7 @@ test_that('bad input', {
 
   expect_snapshot(error = TRUE, surv_reg(mode = ", classification"))
   expect_snapshot(error = TRUE, translate(surv_reg() %>% set_engine("wat")))
-  expect_snapshot(res <- translate(surv_reg() %>% set_engine(NULL)))
+  expect_snapshot(res <- translate(surv_reg() %>% set_engine(NULL)), error = TRUE)
 })
 
 test_that("deprecation warning", {