General Issue: derive_vars_transposed() shouldn't produce list columns

[bundfussr]

Background Information

The functions derive_vars_transposed() and derive_vars_atc() may produce list columns.

Consider for example the ATC variables derivation in the OCCDS vignette:

derive_vars_atc(cm, facm)
#> Warning: Values from `FASTRESC` are not uniquely identified; output will contain
#> list-cols.
#> • Use `values_fn = list` to suppress this warning.
#> • Use `values_fn = {summary_fun}` to summarise duplicates.
#> • Use the following dplyr code to identify duplicates.
#>   {data} |>
#>   dplyr::summarise(n = dplyr::n(), .by = c(USUBJID, FAREFID, FATESTCD)) |>
#>   dplyr::filter(n > 1L)
#> # A tibble: 3 × 8
#>   USUBJID      CMGRPID CMREFID CMDECOD        ATC1CD    ATC2CD    ATC3CD ATC4CD
#>   <chr>        <chr>   <chr>   <chr>          <list>    <list>    <list> <list>
#> 1 BP40257-1001 14      1192056 PARACETAMOL    <chr [1]> <chr [1]> <chr>  <chr> 
#> 2 BP40257-1001 18      2007001 SOLUMEDROL     <chr [3]> <chr [3]> <chr>  <chr> 
#> 3 BP40257-1002 19      2791596 SPIRONOLACTONE <chr [1]> <chr [1]> <chr>  <chr>

The issue is that id_vars = exprs(FAGRPID) is missing in the call.

However, this is not clear from the warning. Furthermore, admiral functions shouldn't produce list columns.

Thus, the uniqueness should be checked in derive_vars_transposed() such that an error is issued if the input results in list columns.

Definition of Done

An error is issued if the input of derive_vars_transposed() results in list columns.