There should be a check to make sure an fit method is registered #634
Description
Our change to move all model definitions into parsnip, have resulting in the following uninformative error when you try to use a model that is only has fit methods defined in extension packages.
library(parsnip)
cubist_rules() %>%
fit(mpg ~., data = mtcars)
#> Error: formula_ is unknown.
pls() %>%
set_mode("regression") %>%
fit(mpg ~., data = mtcars)
#> Error: formula_ is unknown.
library(rules)
#> Loading required package: modeldata
cubist_rules() %>%
fit(mpg ~., data = mtcars)
#> parsnip model object
#>
#>
#> Call:
#> cubist.default(x = x, y = y, committees = 1)
#>
#> Number of samples: 32
#> Number of predictors: 10
#>
#> Number of committees: 1
#> Number of rules: 1Created on 2022-01-13 by the reprex package (v2.0.1)