prompt on parameter extraction when implementation is missing

[simonpcouch]

Introduces the missing implementation prompt as an error on extract_parameter*dials. Only needs added to extract_parameter_set_dials, which is called by extract_parameter_dials. We only add this to the .model_spec methods, as the prompt is raised already for workflows via tidymodels/workflows#175 by then. :)

library(parsnip)

bt_mod <- bag_tree(min_n = tune()) %>%
  set_mode("regression")

extract_parameter_set_dials(bt_mod)
#> Error:
#> ! 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.

extract_parameter_dials(bt_mod, parameter = "min_n")
#> Error:
#> ! 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.

^{Created on 2022-09-09 by the reprex package (v2.0.1)}

Relies on #804 for a more fully readable when the user has supplied an engine.

[hfrick]

Nice!

[hfrick]

if that call to spec_is_loaded() with args that are all derived from x is a common pattern elsewhere in parsnip, it might be worth putting that in its own little wrapper?

[simonpcouch]

Yeah, I feel this.

Something near it is quite common, though usually one or two of these arguments is switched out with a "proposed" slot (like, in set_mode, mode = mode and user_specified_mode = TRUE). Maybe the first argument ought to be x, with defaults to x$ slots, and we specify when needed?

[hfrick]

that sounds like a small, good quality-of-life improvement to me 👍

[github-actions]

This pull request has been automatically locked. If you believe you have found a related problem, please file a new issue (with a reprex: https://reprex.tidyverse.org) and link to this issue.