How to avoid input variable names in tidyr::complete()

In tidyr::complete, I have to input variable names, how to avoid it? In actual, the variable are some many, it's boring to input one by one ... Anyone can help?

library(tidyverse)
    raw_df <- data.frame(cat=c('A','B','C'),sub_category=c('1','2','3'))

Input variable name , the code run well

 raw_df %>% tidyr::complete(cat,sub_category)

Below code can't work--the input way i wished

 raw_df %>% tidyr::complete()

A slightly different approach would be to use expand_grid and pass in all columns of the dataframe unpacked using !!! via an anonymous function. This works but others may have more simple approaches to suggest!

library(tidyverse)

raw_df <- data.frame(cat=c('A','B','C'),sub_category=c('1','2','3'))

raw_df |>
  (\(df) expand_grid(!!!df))()
#> # A tibble: 9 × 2
#>   cat   sub_category
#>   <chr> <chr>       
#> 1 A     1           
#> 2 A     2           
#> 3 A     3           
#> 4 B     1           
#> 5 B     2           
#> 6 B     3           
#> 7 C     1           
#> 8 C     2           
#> 9 C     3