In R: how to pass function name (not as character) as an argument to another inner function without loss of initial function name?

Question

I have two functions:

1. Worker that does the job
2. Boss that calls the "Worker" and ask it to execute given function called by name

If I call Worker directly it receives function body and its name so it can use both. But if I call the Worker through the Boss, the Boss masks name of the function from the Worker as FUN

require(magrittr)    
require(dplyr)

df <- data.frame(one = c(1,1,1), two = c(1,3,NA))

Worker <- function(df, feature, FUN, ...) {
  newvarname <- paste0(substitute(FUN), feature)
  df %>% mutate(!!newvarname := FUN(!!as.name(feature), ...))
}

Boss <- function(df, feature, FUN, ...) {
  df %>% Worker(feature, FUN, ...)
}

Boss(df, "two", mean, na.rm = T)
   #   one two FUNtwo
   # 1   1   1      2
   # 2   1   3      2
   # 3   1  NA      2
Worker(df, "one", mean)
   #   one two meanone
   # 1   1   1       1
   # 2   1   3       1
   # 3   1  NA       1

I tired to play with quote/quo/enquo/substitute/get/match.fun, but nothing helped. Does it mean, that R cannot pass a whole function object - both name and body - as an argument?

Answer 1

Here is one way to handle it with some rlang:

library(rlang)

df <- data.frame(one = c(1,1,1), two = c(1,3,NA))

Worker <- function(df, feature, FUN, ...) {

    if (!is_quosure(FUN)) {
        fun_q <- quo(FUN)
        newvarname <- paste0(substitute(FUN), feature)
    }
    else {
        fun_q <- FUN
        newvarname <- paste0(quo_text(fun_q), feature)
    }

    df %>% mutate(!!newvarname := eval(fun_q)(!!as.name(feature), ...))
}

Boss <- function(df, feature, FUN, ...) {
    fun_q <- enquo(FUN)
    df %>% Worker(feature, fun_q, ...)
}

Boss(df, "two", mean, na.rm = T)

  one two meantwo
1   1   1       2
2   1   3       2
3   1  NA       2

Worker(df, "one", mean)

  one two meanone
1   1   1       1
2   1   3       1
3   1  NA       1