prompt on add_model() when missing implementation

DESCRIPTION

@@ -23,7 +23,7 @@ Imports:
     glue (>= 1.6.2),
     hardhat (>= 1.2.0),
     lifecycle (>= 1.0.1),
-    parsnip (>= 1.0.0),
+    parsnip (>= 1.0.1.9000),
     rlang (>= 1.0.3),
     tidyselect (>= 1.1.2),
     vctrs (>= 0.4.1)
@@ -45,6 +45,8 @@ Config/Needs/website:
     tidyr,
     tidyverse/tidytemplate,
     yardstick
+Remotes:
+    tidymodels/parsnip
 Config/testthat/edition: 3
 Encoding: UTF-8
 Roxygen: list(markdown = TRUE)

R/fit-action-model.R

@@ -190,5 +190,13 @@ new_action_model <- function(spec, formula, ..., call = caller_env()) {
     abort("`formula` must be a formula, or `NULL`.", call = call)
   }
 
+  if (!parsnip::spec_is_loaded(spec = spec)) {
+    parsnip::prompt_missing_implementation(
+      spec = spec,
+      prompt = cli::cli_abort,
+      call = call
+    )
+  }
+
   new_action_fit(spec = spec, formula = formula, subclass = "action_model")
 }

tests/testthat/_snaps/fit-action-model.md

@@ -15,6 +15,26 @@
       ! `spec` must have a known mode.
       i Set the mode of `spec` by using `parsnip::set_mode()` or by setting the mode directly in the parsnip specification function.
 
+# prompt on spec without a loaded implementation (#174)
+
+    Code
+      add_model(workflow, mod)
+    Condition
+      Error in `add_model()`:
+      ! parsnip could not locate an implementation for `bag_tree` regression model specifications.
+      i The parsnip extension package baguette implements support for this specification.
+      i Please install (if needed) and load to continue.
+
+---
+
+    Code
+      workflow(spec = mod)
+    Condition
+      Error in `add_model()`:
+      ! parsnip could not locate an implementation for `bag_tree` regression model specifications.
+      i The parsnip extension package baguette implements support for this specification.
+      i Please install (if needed) and load to continue.
+
 # cannot add two models
 
     Code

tests/testthat/test-fit-action-model.R

@@ -22,6 +22,16 @@ test_that("model must contain a known mode (#160)", {
   })
 })
 
+test_that("prompt on spec without a loaded implementation (#174)", {
+  mod <- parsnip::bag_tree() %>%
+    parsnip::set_mode("regression")
+
+  workflow <- workflow()
+
+  expect_snapshot(error = TRUE, add_model(workflow, mod))
+  expect_snapshot(error = TRUE, workflow(spec = mod))
+})
+
 test_that("cannot add two models", {
   mod <- parsnip::linear_reg()
   mod <- parsnip::set_engine(mod, "lm")