`drop = TRUE` in `scale_*_manual` no longer drops unused factors (as of v3.3.4)

[andrewbaxter439]

As of updates 3.3.4 and 3.3.5 the argument to drop unused factor levels seems to have stopped working:

library(tidyverse)

tribble(~group, ~val,
        "a", 5,
        "b", 6,
        "c", 7) %>% 
  ggplot(aes(group, val, fill = group)) +
  geom_col() +
  scale_fill_manual(values = c(
    "a" = "lightblue",
    "b" = "lightgreen",
    "c" = "maroon",
    "d" = "grey"
  ),
  drop = TRUE)

^{Created on 2021-08-25 by the reprex package (v2.0.0)}

Session info

sessionInfo()
#> R version 4.1.0 (2021-05-18)
#> Platform: x86_64-w64-mingw32/x64 (64-bit)
#> Running under: Windows 10 x64 (build 19041)
#> 
#> Matrix products: default
#> 
#> locale:
#> [1] LC_COLLATE=English_United Kingdom.1252 
#> [2] LC_CTYPE=English_United Kingdom.1252   
#> [3] LC_MONETARY=English_United Kingdom.1252
#> [4] LC_NUMERIC=C                           
#> [5] LC_TIME=English_United Kingdom.1252    
#> 
#> attached base packages:
#> [1] stats     graphics  grDevices utils     datasets  methods   base     
#> 
#> other attached packages:
#> [1] forcats_0.5.1   stringr_1.4.0   dplyr_1.0.5     purrr_0.3.4    
#> [5] readr_1.4.0     tidyr_1.1.3     tibble_3.1.1    ggplot2_3.3.5  
#> [9] tidyverse_1.3.1
#> 
#> loaded via a namespace (and not attached):
#>  [1] tidyselect_1.1.0  xfun_0.22         haven_2.4.0       colorspace_2.0-0 
#>  [5] vctrs_0.3.7       generics_0.1.0    htmltools_0.5.1.1 yaml_2.2.1       
#>  [9] utf8_1.2.1        rlang_0.4.10      pillar_1.6.0      glue_1.4.2       
#> [13] withr_2.4.2       DBI_1.1.1         dbplyr_2.1.1      modelr_0.1.8     
#> [17] readxl_1.3.1      lifecycle_1.0.0   munsell_0.5.0     gtable_0.3.0     
#> [21] cellranger_1.1.0  rvest_1.0.0       evaluate_0.14     labeling_0.4.2   
#> [25] knitr_1.32        ps_1.6.0          curl_4.3          fansi_0.4.2      
#> [29] highr_0.9         broom_0.7.6       Rcpp_1.0.6        backports_1.2.1  
#> [33] scales_1.1.1      jsonlite_1.7.2    mime_0.10         farver_2.1.0     
#> [37] fs_1.5.0          hms_1.0.0         digest_0.6.27     stringi_1.5.3    
#> [41] grid_4.1.0        cli_2.4.0         tools_4.1.0       magrittr_2.0.1   
#> [45] crayon_1.4.1      pkgconfig_2.0.3   ellipsis_0.3.1    xml2_1.3.2       
#> [49] reprex_2.0.0      lubridate_1.7.10  assertthat_0.2.1  rmarkdown_2.7    
#> [53] httr_1.4.2        rstudioapi_0.13   R6_2.5.0          compiler_4.1.0

---

By contrast, the code running on v3.3.3 produces the desired result:

^{Created on 2021-08-25 by the reprex package (v2.0.0)}

[andrewbaxter439]

Oops, after a bit more digging I did see it's already opened in #4511 and may be fixed by #4547 - do ignore