Make userfacing set_* functions generic

NAMESPACE

@@ -57,6 +57,9 @@ S3method(req_pkgs,model_fit)
 S3method(req_pkgs,model_spec)
 S3method(required_pkgs,model_fit)
 S3method(required_pkgs,model_spec)
+S3method(set_args,model_spec)
+S3method(set_engine,model_spec)
+S3method(set_mode,model_spec)
 S3method(tidy,"_LiblineaR")
 S3method(tidy,"_elnet")
 S3method(tidy,"_fishnet")

R/arguments.R

@@ -49,6 +49,11 @@ check_eng_args <- function(args, obj, core_args) {
 #'
 #' @export
 set_args <- function(object, ...) {
+  UseMethod("set_args")
+}
+
+#' @export
+set_args.model_spec <- function(object, ...) {
   the_dots <- enquos(...)
   if (length(the_dots) == 0)
     rlang::abort("Please pass at least one named argument.")
@@ -75,6 +80,11 @@ set_args <- function(object, ...) {
 #' @rdname set_args
 #' @export
 set_mode <- function(object, mode) {
+  UseMethod("set_mode")
+}
+
+#' @export
+set_mode.model_spec <- function(object, mode) {
   cls <- class(object)[1]
   if (rlang::is_missing(mode)) {
     spec_modes <- rlang::env_get(get_model_env(), paste0(cls, "_modes"))

R/engines.R

@@ -105,10 +105,12 @@ load_libs <- function(x, quiet, attach = FALSE) {
 #'
 #' @export
 set_engine <- function(object, engine, ...) {
+  UseMethod("set_engine")
+}
+
+#' @export
+set_engine.model_spec <- function(object, engine, ...) {
   mod_type <- class(object)[1]
-  if (!inherits(object, "model_spec")) {
-    rlang::abort("`object` should have class 'model_spec'.")
-  }
 
   if (rlang::is_missing(engine)) {
     stop_missing_engine(mod_type)

tests/testthat/_snaps/args_and_modes.md

@@ -0,0 +1,16 @@
+# set_* functions error when input isn't model_spec
+
+    Code
+      set_mode(mtcars, "regression")
+    Condition
+      Error in `UseMethod()`:
+      ! no applicable method for 'set_mode' applied to an object of class "data.frame"
+
+---
+
+    Code
+      set_args(mtcars, blah = "blah")
+    Condition
+      Error in `UseMethod()`:
+      ! no applicable method for 'set_args' applied to an object of class "data.frame"
+

tests/testthat/_snaps/misc.md

@@ -14,3 +14,11 @@
       Computational engine: rpart 
 
 
+# set_engine works as a generic
+
+    Code
+      set_engine(mtcars, "rpart")
+    Condition
+      Error in `UseMethod()`:
+      ! no applicable method for 'set_engine' applied to an object of class "data.frame"
+

tests/testthat/test_args_and_modes.R

@@ -101,4 +101,13 @@ test_that("unavailable modes for an engine and vice-versa", {
   )
 })
 
+test_that("set_* functions error when input isn't model_spec", {
+  expect_snapshot(error = TRUE,
+                  set_mode(mtcars, "regression")
+  )
+
+  expect_snapshot(error = TRUE,
+                  set_args(mtcars, blah = "blah")
+  )
+})
 

tests/testthat/test_misc.R

@@ -106,3 +106,9 @@ test_that('model type functions message informatively with unknown implementatio
       set_engine("rpart")
   )
 })
+
+test_that('set_engine works as a generic', {
+  expect_snapshot(error = TRUE,
+    set_engine(mtcars, "rpart")
+  )
+})