rlang::enexprs() works inconsistently

Question

I'm learning more about programming with R but I'm puzzled as to the behavior below. Essentially minor changes/variations in the code can produce different results. Any thoughts on why no named argument example below doesn't return the consistent results?

1. no named arguments -- only lists last formula
2. named arguments --works as expected
3. including the data.frame in the function (unnamed arguments) -- work as expected

No named arguments (only returns last formula

library(tidyverse)
library(rlang)

test <- function(.data, ...) {
  cols <- rlang::enexprs(...)
  mtcars %>% 
    reframe(
      !!!cols
    )
}

test(
  median(mpg),
  mean(vs)
)

named arguments

test <- function(.data,...){
  
  cols <-  rlang::enexprs(...)
  mtcars %>% 
    reframe(
      !!!cols
    )
    
  
  
}

test(
  median=median(mpg)
  ,mean=mean(vs)
 
  )

include data.frame unnamed argument

test <- function(.data, ...) {
  cols <- rlang::enexprs(...)
  .data %>% 
    reframe(
      !!!cols
    )
}

test(
  mtcars,
  median(mpg),
  mean(vs)
)
    

Answer 1

As Jaret Mamrot already suggests in the comments, the problem is in your .data arg. Either drop it as suggested by Jaret or use it. In either case named arguments are working fine:

library(tidyverse)
library(rlang)

test <- function(.dat, ...) {
  cols <- rlang::enexprs(...)
  .dat %>% # <- here we actually use the .data arg
    reframe(
      !!! cols
    )
}

test(mtcars,
  median(mpg),
  mean(vs)
)
#>   median(mpg) mean(vs)
#> 1        19.2   0.4375

test(mtcars,
  median = median(mpg),
  mean   = mean(vs)
)
#>   median   mean
#> 1   19.2 0.4375

^{Created on 2023-07-25 with reprex v2.0.2}