!!as.name() does not work with nested tibbles using map2()

[vovoch]

I ran into inability to use !!as.name() with .x or .y input variables inside of mutate( map2( rename(...) ).
I provide a reprex with several attempts below.

Also I would like to add it is very strange but .x and .y global variables are not visible on the Environment tab in Data or Values sections in RStudio 1.3.1073. It is a problem if you used them for debugging previously without further rm(). The only way to know about their presence is to print them in the console.

library(tidyverse)

df <- tibble(
  var_name = "new_name",
  data = list(data.frame(foo = 1))
)

df
#> # A tibble: 1 x 2
#>   var_name data            
#>   <chr>    <list>          
#> 1 new_name <df[,1] [1 x 1]>

df$data
#> [[1]]
#>   foo
#> 1   1

# OK example 1
df %>% mutate(data = map2(data, var_name, ~.x %>% mutate(foo = .y))) %>% .$data
#> [[1]]
#>        foo
#> 1 new_name

# OK example 2
df %>% mutate(data = map(data, ~.x %>% rename(!!as.name("new_name") := foo))) %>% .$data
#> [[1]]
#>   new_name
#> 1        1

# ERROR example 1
df %>% mutate(data = map2(data, "new_name", ~.x %>% rename(!!as.name(.y) := foo)))
#> Error in as.name(.y): object '.y' not found

# ERROR example 2
df %>% mutate(data = map2(data, var_name, ~.x %>% rename(!!as.name(.y) := foo)))
#> Error in as.name(.y): object '.y' not found

# ERROR example 3
df %>% mutate(data = map2(var_name, data, ~.y %>% rename(!!as.name(.x) := foo)))
#> Error in as.name(.x): object '.x' not found

# Example with global .y value 1
.y <- "global"
df %>% mutate(data = map2(data, var_name, ~.x %>% rename(!!as.name(.y) := foo))) %>% .$data
#> [[1]]
#>   global
#> 1      1

# Example with global .y value 2
.y <- list("a")
df %>% mutate(data = map2(data, var_name, ~.x %>% rename(!!as.name(.y) := foo))) %>% .$data
#> Error in as.name(.y): invalid type/length (symbol/1) in vector allocation

# repeating ERROR example 2
rm(.y)
df %>% mutate(data = map2(data, var_name, ~.x %>% rename(!!as.name(.y) := foo))) %>% .$data
#> Error in as.name(.y): object '.y' not found

^{Created on 2020-09-01 by the reprex package (v0.3.0)}

[lionel-]

This is expected. !! happens very early, at the time the first mutate() is called. At that point, the purrr lambda isn't executing yet, so there's no .x or .y argument.

We have plans to possibly change that in the next major version of rlang: r-lib/rlang#845. Maybe this would be too large of a breaking change and we can't go through with it.