How to create reusable dplyr::case_when() functions?

case_when_factory.R

# case_when factory: ----------------------------------------------
create_case_when <- function(..., vars = "x") {
  fun_fmls <- purrr::map(rlang::set_names(vars), ~ rlang::missing_arg())
  fun_body <- substitute({
    for (name in var) {
      symb <- rlang::eval_bare(rlang::sym(name))
      var <- rlang::eval_tidy(rlang::enquo(symb))
      assign(name, var)
    }
    forms <- purrr::map(formulas, rlang::`f_env<-`, value = environment())
    do.call(dplyr::case_when, forms)
  })
  formulas <- rlang::dots_list(...)
  var <- vars
  structure(
    rlang::new_function(fun_fmls, fun_body),
    class = c("case_when", "function")
  )
}

formulas <- function(x, ...) UseMethod("formulas")

formulas.case_when <- function(x, ...) get("formulas", envir = environment(x))

print.case_when <- function(x, ...) {
  formulas <- formulas(x)
  n <- length(formulas)
  out <- capture.output(purrr::walk(formulas, print, showEnv = FALSE))
  out <- c(crayon::cyan("<CASE WHEN>"), 
           crayon::magenta(paste(n, "conditions:")), 
           crayon::green(paste("->", out)), "")
  cat(paste0(out, collapse = "\n"))
  invisible(x)
}

# Applications -----------------------------------------------------------
# One-dimension case_when() ----------------------------------------------
library(dplyr)

people <-
  tribble(
    ~name, ~sex, ~seek,
    "Henry", "M", "F",
    "Mary", "F", "M",
  )

cw_sex <- create_case_when(x == "F" ~ "Woman",
                           x == "M" ~ "Man",
                           TRUE ~ as.character(x),
                           vars = c("x"))

print(cw_sex)

people %>% mutate(sex_label = cw_sex(sex), seek_label = cw_sex(seek))

# Two-dimensions case_when() ----------------------------------------------
people2 <-
  tribble(
    ~name, ~sex, ~lang,
    "Henry", "M", "en",
    "Mary", "F", "en",
    "Jacques", "M", "fr",
    "Mireille", "F", "fr"
  )

cw_sex2 <- create_case_when(x == "F" & y == "en" ~ "Woman",
                            x == "F" & y == "fr" ~ "Femme",
                            x == "M" & y == "en" ~ "Man",
                            x == "M" & y == "fr" ~ "Homme",
                            TRUE ~ as.character(x),
                            vars = c("x", "y"))

print(cw_sex2)

people2 %>% mutate(sex_label = cw_sex2(sex, lang))