use invoke_map to pass variable names as args - r

Question

I would like to use invoke_map to call a list of functions. I have a set of variable names that I would like to use as arguments to each of the functions. Ultimately the variable names will used with group_by.
Here's an example:
library(dplyr)
library(purrr)
first_fun <- function(...){
by_group = quos(...)
mtcars %>%
group_by(!!!by_group) %>%
count()
}
second_fun <- function(...){
by_group = quos(...)
mtcars %>%
group_by(!!!by_group) %>%
summarise(avg_wt = mean(wt))
}
first_fun(mpg, cyl) # works
second_fun(mpg, cyl) # works
both_funs <- list(first_fun, second_fun)
both_funs %>%
invoke_map(mpg, cyl) # What do I do here?
I have tried various attempts to put the variable names in quotes, enquo them, use vars, reference .data$mpg, etc, but I am stabbing in the dark a bit.

Answer 1

The issue is not that you're using dots, it's that you're using names and when map2_impl is called these arguments are evaluated.
Try this and explore the environment:
debugonce(map2)
both_funs %>% invoke_map("mpg", "cyl")
This works on the other hand:
first_fun2 <- function(...){
mtcars %>%
{do.call(group_by_,list(.,unlist(list(...))))} %>%
count()
}
second_fun2 <- function(...){
mtcars %>%
{do.call(group_by_,list(.,unlist(list(...))))} %>%
summarise(avg_wt = mean(wt))
}
both_funs2 <- list(first_fun2, second_fun2)
both_funs2 %>% invoke_map("mpg", "cyl")
# [[1]]
# # A tibble: 25 x 2
# # Groups: mpg [25]
# mpg n
# <dbl> <int>
# 1 10.4 2
# 2 13.3 1
# 3 14.3 1
# 4 14.7 1
# 5 15.0 1
# 6 15.2 2
# 7 15.5 1
# 8 15.8 1
# 9 16.4 1
# 10 17.3 1
# # ... with 15 more rows
#
# [[2]]
# # A tibble: 25 x 2
# mpg avg_wt
# <dbl> <dbl>
# 1 10.4 5.3370
# 2 13.3 3.8400
# 3 14.3 3.5700
# 4 14.7 5.3450
# 5 15.0 3.5700
# 6 15.2 3.6075
# 7 15.5 3.5200
# 8 15.8 3.1700
# 9 16.4 4.0700
# 10 17.3 3.7300
# # ... with 15 more rows