case_when() needs to throw a better error when conditions are matrices

[DarwinAwardWinner]

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---

I had some code that was passing matrices as the conditions to a case_when statement. Previously, case_when would implicitly convert these matrices to vectors, but at some point it stopped doing that. However, I don't think this was an intentional behavior change, because depending on how exactly one calls case_when on matrix conditions, it can produce one of several different error messages or return a value of the wrong length (see reprex below demonstrating 3 different behaviors). None of the error messages hint at the underlying problem, which made debugging this issue after a package update very difficult.

If passing matrices as the conditions to case_when is not an intended usage, I would expect it to produce an interpretable error message to that effect.

library(dplyr)
#> 
#> Attaching package: 'dplyr'
#> The following objects are masked from 'package:stats':
#> 
#>     filter, lag
#> The following objects are masked from 'package:base':
#> 
#>     intersect, setdiff, setequal, union
library(assertthat)

x <- matrix(rnorm(36), ncol = 6)

## Each of the following generates a different error
{
  y1 <- case_when(
    !is.finite(x) ~ "Invalid",
    .default = "Default"
  )
  assert_that(length(y1) == length(x))
}
#> Error: length(y1) not equal to length(x)

{
  y2 <- case_when(
    !is.finite(x) ~ "Invalid",
    x < 0 ~ "Negative",
    .default = "Default"
  )
  assert_that(length(y2) == length(x))
}
#> Error in `vec_slice()`:
#> ! Can't subset elements past the end.
#> ℹ Locations 8, 10, 13, …, 35, and 36 don't exist.
#> ℹ There are only 6 elements.
#> Backtrace:
#>     ▆
#>  1. ├─dplyr::case_when(...)
#>  2. │ └─dplyr:::vec_case_when(...)
#>  3. │   └─vctrs::vec_slice(value, loc)
#>  4. └─vctrs (local) `<fn>`()
#>  5.   └─vctrs:::stop_subscript_oob(...)
#>  6.     └─vctrs:::stop_subscript(...)
#>  7.       └─rlang::abort(...)

{
  y3 <- case_when(
    !is.finite(x) ~ "Invalid",
    x < 0 ~ "Negative",
    x > 0 ~ "Positive",
    x == 0 ~ "Zero"
  )
  assert_that(length(y3) == length(x))
}
#> Error in if (!any(are_unused)) {: missing value where TRUE/FALSE needed

## Everything works fine if you convert x to a vector
{
  xvec <- as.vector(x)
  yvec <- case_when(
    !is.finite(xvec) ~ "Invalid",
    xvec < 0 ~ "Negative",
    xvec > 0 ~ "Positive",
    xvec == 0 ~ "Zero"
  )
  assert_that(length(yvec) == length(xvec))
}
#> [1] TRUE

^{Created on 2023-05-30 with reprex v2.0.2}

[DarwinAwardWinner]

Session info:

> sessionInfo()
R version 4.2.0 (2022-04-22)
Platform: x86_64-pc-linux-gnu (64-bit)
Running under: CentOS Linux 7 (Core)

Matrix products: default
BLAS/LAPACK: /hpc/packages/minerva-centos7/intel/parallel_studio_xe_2019/compilers_and_libraries_2019.0.117/linux/mkl/lib/intel64_lin/libmkl_gf_lp64.so

locale:
 [1] LC_CTYPE=en_US.UTF-8       LC_NUMERIC=C
 [3] LC_TIME=en_US.UTF-8        LC_COLLATE=en_US.UTF-8
 [5] LC_MONETARY=en_US.UTF-8    LC_MESSAGES=en_US.UTF-8
 [7] LC_PAPER=en_US.UTF-8       LC_NAME=C
 [9] LC_ADDRESS=C               LC_TELEPHONE=C
[11] LC_MEASUREMENT=en_US.UTF-8 LC_IDENTIFICATION=C

attached base packages:
[1] stats     graphics  grDevices utils     datasets  methods   base

other attached packages:
[1] assertthat_0.2.1 dplyr_1.1.2      colorout_1.2-2

loaded via a namespace (and not attached):
 [1] fansi_1.0.4      utf8_1.2.3       crayon_1.5.2     R6_2.5.1
 [5] lifecycle_1.0.3  magrittr_2.0.3   pillar_1.9.0     rlang_1.1.1
 [9] cli_3.6.0        vctrs_0.6.2      generics_0.1.3   glue_1.6.2
[13] compiler_4.2.0   pkgconfig_2.0.3  tidyselect_1.2.0 tibble_3.2.1

Session info from other machine that also exhibits the issue:

> sessionInfo()
R version 4.3.0 (2023-04-21)
Platform: x86_64-apple-darwin22.4.0 (64-bit)
Running under: macOS Ventura 13.3.1

Matrix products: default
BLAS:   /usr/local/Cellar/openblas/0.3.23/lib/libopenblasp-r0.3.23.dylib 
LAPACK: /usr/local/Cellar/r/4.3.0_1/lib/R/lib/libRlapack.dylib;  LAPACK version 3.11.0

locale:
[1] en_US.UTF-8/en_US.UTF-8/en_US.UTF-8/C/en_US.UTF-8/en_US.UTF-8

time zone: America/New_York
tzcode source: internal

attached base packages:
[1] graphics  grDevices utils     datasets  stats     methods   base     

other attached packages:
 [1] assertthat_0.2.1 reprex_2.0.2     tidyr_1.3.0      future_1.32.0   
 [5] devtools_2.4.5   usethis_2.1.6    openxlsx_4.2.5.2 magrittr_2.0.3  
 [9] dplyr_1.1.2      rex_1.2.1        glue_1.6.2       stringr_1.5.0   
[13] ggplot2_3.4.2    colorout_1.2-2  

loaded via a namespace (and not attached):
 [1] gtable_0.3.3      xfun_0.39         htmlwidgets_1.6.2 remotes_2.4.2    
 [5] processx_3.8.1    callr_3.7.3       vctrs_0.6.2       tools_4.3.0      
 [9] ps_1.7.5          generics_0.1.3    parallel_4.3.0    tibble_3.2.1     
[13] fansi_1.0.4       pkgconfig_2.0.3   lifecycle_1.0.3   compiler_4.3.0   
[17] munsell_0.5.0     codetools_0.2-19  httpuv_1.6.10     htmltools_0.5.5  
[21] yaml_2.3.7        later_1.3.1       pillar_1.9.0      crayon_1.5.2     
[25] urlchecker_1.0.1  ellipsis_0.3.2    cachem_1.0.8      sessioninfo_1.2.2
[29] mime_0.12         parallelly_1.35.0 tidyselect_1.2.0  zip_2.3.0        
[33] digest_0.6.31     stringi_1.7.12    purrr_1.0.1       listenv_0.9.0    
[37] fastmap_1.1.1     grid_4.3.0        colorspace_2.1-0  cli_3.6.1        
[41] pkgbuild_1.4.0    utf8_1.2.3        clipr_0.8.0       withr_2.5.0      
[45] prettyunits_1.1.1 scales_1.2.1      promises_1.2.0.1  rmarkdown_2.21   
[49] globals_0.16.2    evaluate_0.21     memoise_2.0.1     shiny_1.7.4      
[53] knitr_1.42        miniUI_0.1.1.1    profvis_0.3.8     rlang_1.1.1      
[57] Rcpp_1.0.10       xtable_1.8-4      pkgload_1.3.2     rstudioapi_0.14  
[61] R6_2.5.1          fs_1.6.2    

[DavisVaughan]

Yea we don't intend for matrices to be passed through as conditions. We probably need an additional check here for dim

dplyr/R/vec-case-when.R

Line 54 in 16b472f

check_logical(condition, arg = condition_arg, call = call)