Better error message for empty tidyselect quosure

[sda030]

The following empty tidyselect::all_of() would have given an empty data frame in dplyr::select() but here gives a rather uninformative error. Perhaps a "Selection is empty.".

---

Brief description of the problem

expect_variables <- c()
tidyr::unite(mtcars, col = "merged", tidyselect::all_of(expect_variables))
#> Error in `df_append()`:
#> ! `after` must be a whole number, not an integer `NA`.
#> ℹ This is an internal error that was detected in the tidyr package.
#>   Please report it at <https://github.com/tidyverse/tidyr/issues> with a reprex
#>   (<https://tidyverse.org/help/>) and the full backtrace.
---
Backtrace:
    ▆
 1. ├─mtcars %>% ...
 2. ├─tidyr::unite(...)
 3. └─tidyr:::unite.data.frame(...)
 4.   └─tidyr:::df_append(after = after)
 5.     └─tidyr:::check_number_whole(after, min = 0L, max = n, .internal = TRUE)
 6.       └─tidyr:::.rlang_types_check_number(...)
 7.         └─tidyr (local) .stop(x, what, ...)
 8.           └─tidyr:::stop_input_type(...)
 9.             └─rlang::abort(message, ..., call = call, arg = arg)

^{Created on 2024-04-15 with reprex v2.1.0}

Session info

sessioninfo::session_info()
#> ─ Session info ───────────────────────────────────────────────────────────────
#>  setting  value
#>  version  R version 4.3.2 (2023-10-31 ucrt)
#>  os       Windows 11 x64 (build 22621)
#>  system   x86_64, mingw32
#>  ui       RTerm
#>  language (EN)
#>  collate  nb.utf8
#>  ctype    nb.utf8
#>  tz       Europe/Oslo
#>  date     2024-04-15
#>  pandoc   3.1.12.3 @ C:/PROGRA~1/Pandoc/ (via rmarkdown)
#> 
#> ─ Packages ───────────────────────────────────────────────────────────────────
#>  package     * version date (UTC) lib source
#>  cli           3.6.2   2023-12-11 [1] RSPM (R 4.3.0)
#>  digest        0.6.35  2024-03-11 [1] CRAN (R 4.3.3)
#>  dplyr         1.1.4   2023-11-17 [1] RSPM (R 4.3.0)
#>  evaluate      0.23    2023-11-01 [1] RSPM (R 4.3.0)
#>  fansi         1.0.6   2023-12-08 [1] CRAN (R 4.3.2)
#>  fastmap       1.1.1   2023-02-24 [1] CRAN (R 4.2.3)
#>  fs            1.6.3   2023-07-20 [1] CRAN (R 4.3.1)
#>  generics      0.1.3   2022-07-05 [1] CRAN (R 4.2.3)
#>  glue          1.7.0   2024-01-09 [1] CRAN (R 4.3.2)
#>  htmltools     0.5.8.1 2024-04-04 [1] CRAN (R 4.3.3)
#>  knitr         1.45    2023-10-30 [1] RSPM (R 4.3.0)
#>  lifecycle     1.0.4   2023-11-07 [1] RSPM (R 4.3.0)
#>  magrittr      2.0.3   2022-03-30 [1] CRAN (R 4.2.3)
#>  pillar        1.9.0   2023-03-22 [1] CRAN (R 4.2.3)
#>  pkgconfig     2.0.3   2019-09-22 [1] CRAN (R 4.2.3)
#>  purrr         1.0.2   2023-08-10 [1] CRAN (R 4.3.1)
#>  R.cache       0.16.0  2022-07-21 [1] CRAN (R 4.2.3)
#>  R.methodsS3   1.8.2   2022-06-13 [1] CRAN (R 4.2.2)
#>  R.oo          1.26.0  2024-01-24 [1] CRAN (R 4.3.2)
#>  R.utils       2.12.3  2023-11-18 [1] RSPM (R 4.3.0)
#>  R6            2.5.1   2021-08-19 [1] CRAN (R 4.2.3)
#>  reprex        2.1.0   2024-01-11 [1] CRAN (R 4.3.1)
#>  rlang         1.1.3   2024-01-10 [1] CRAN (R 4.3.2)
#>  rmarkdown     2.26    2024-03-05 [1] CRAN (R 4.3.3)
#>  rstudioapi    0.15.0  2023-07-07 [1] CRAN (R 4.3.1)
#>  sessioninfo   1.2.2   2021-12-06 [1] CRAN (R 4.2.3)
#>  styler        1.10.2  2023-08-29 [1] RSPM (R 4.3.0)
#>  tibble        3.2.1   2023-03-20 [1] CRAN (R 4.2.3)
#>  tidyr         1.3.1   2024-01-24 [1] CRAN (R 4.3.2)
#>  tidyselect    1.2.1   2024-03-11 [1] CRAN (R 4.3.3)
#>  utf8          1.2.4   2023-10-22 [1] RSPM (R 4.3.0)
#>  vctrs         0.6.5   2023-12-01 [1] RSPM (R 4.3.0)
#>  withr         3.0.0   2024-01-16 [1] RSPM (R 4.3.1)
#>  xfun          0.42    2024-02-08 [1] CRAN (R 4.3.2)
#>  yaml          2.3.8   2023-12-11 [1] RSPM (R 4.3.0)
#> 
#>  [1] C:/Users/py128/AppData/Local/R/win-library
#>  [2] C:/Program Files/R/R-4.3.2/library
#> 
#> ──────────────────────────────────────────────────────────────────────────────

[DavisVaughan]

Thanks for the report!

Note to self:

This occurs because from_vars here is integer():

tidyr/R/unite.R

Line 48 in c6c126a

from_vars <- tidyselect::eval_select(expr(c(...)), data, allow_rename = FALSE)

Resulting in an NA for first_pos here:

tidyr/R/unite.R

Line 72 in c6c126a

first_pos <- which(names(data) %in% names(from_vars))[1]

I think we have two options:

• Error if from_vars is empty
• Return a column named using col with each cell filled with "", i.e. the "initial" reduction value that would theoretically be built upon if you would have actually selected columns. It would be positioned at the end of the data frame.

[sda030]

Or both options?
ignore_empty_selection = FALSE
=> Error
Otherwise return with empty cell col?