Allow use of select helpers in col_exists()

[rich-iannone]

Allowing col_exists() to use select helpers would be useful for checking the presence of columns that match a pattern or begin with a known prefix.

[yjunechoe]

Now possible!

get_info <- function(x) {
  suppressMessages(interrogate(x)) %>% 
    el("validation_set") %>% 
    dplyr::select(5:7, 15) %>% 
    dplyr::mutate(column = unlist(column))
}

create_agent(small_table) %>% 
  col_exists(
    columns = starts_with("date"),
    label = "The time column {.col} exists"
  ) %>% 
  get_info()
#> # A tibble: 2 × 4
#>   assertion_type columns_expr            column    label                           
#>   <chr>          <chr>                   <chr>     <chr>                           
#> 1 col_exists     "starts_with(\"date\")" date_time The time column date_time exists
#> 2 col_exists     "starts_with(\"date\")" date      The time column date exists

create_agent(small_table) %>% 
  col_exists(
    columns = where(lubridate::is.timepoint),
    label = "The time column {.col} exists"
  ) %>% 
  get_info()
#> # A tibble: 2 × 4
#>   assertion_type columns_expr                   column    label                           
#>   <chr>          <chr>                          <chr>     <chr>                           
#> 1 col_exists     where(lubridate::is.timepoint) date_time The time column date_time exists
#> 2 col_exists     where(lubridate::is.timepoint) date      The time column date exists