Double intercept when used in a workflow with a formula as preprocessor

[hfrick]

Two paths through parsnip's interface matrix (formula/matrix) can produce a double intercept when used in a workflow with a formula as the preprocessor.

This is the root cause for tidymodels/censored#272 and tidymodels/workflows#210. Opening the issue here because parsnip is the place to fix this.

library(workflows)
library(parsnip)

# form_xy()
workflow() %>%
  add_formula(mpg ~ cyl + disp + hp) %>%
  add_model(linear_reg(penalty = 0.1, engine = "glmnet"), formula = mpg ~ .) %>%
  fit(data = mtcars) %>%
  extract_fit_engine() %>%
  coef() %>%
  rownames()
#> [1] "(Intercept)"   "`(Intercept)`" "cyl"           "disp"         
#> [5] "hp"

# form_form()
workflow() %>%
  add_formula(mpg ~ cyl + disp + hp) %>%
  add_model(linear_reg(engine = "lm"), formula = mpg ~ .) %>%
  fit(data = mtcars) %>%
  extract_fit_engine() %>%
  coef() %>%
  names()
#> [1] "(Intercept)"   "`(Intercept)`" "cyl"           "disp"         
#> [5] "hp"

^{Created on 2023-12-01 with reprex v2.0.2}

[github-actions]

This issue 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.