`mutate(x = across(c(a, b))` should error

[mgirlich]

In dplyr a nested tibble is created which is not possible in dbplyr, so this should error

library(dplyr, warn.conflicts = FALSE)
suppressMessages(devtools::load_all("~/GitHub/dbplyr/"))


tibble(a = 1, b = 2) %>% 
  mutate(a = 2, x = across())
#> # A tibble: 1 × 3
#>       a     b   x$a    $b
#>   <dbl> <dbl> <dbl> <dbl>
#> 1     2     2     2     2

lazy_frame(a = 1, b = 2) %>% 
  mutate(a = 2, x = across())
#> <SQL>
#> SELECT `a`, `b`
#> FROM (
#>   SELECT 2.0 AS `a`, `b`
#>   FROM `df`
#> ) `q01`

^{Created on 2022-01-19 by the reprex package (v2.0.1)}

TEST

test_that("mutate() error if gets multiple columns in across()", {
  df <- lazy_frame(a = 1, b = 2)
  expect_snapshot({
    (expect_error(mutate(df, a = 2, x = across())))
  })
})