Unable to specify a border partially across merged columns in header, even with fix_border_issues()

[jmobrien]

I'm encountering a border + merging issue that doesn't seem to be addressed by current tools. Reprex below

(Reprex's simplicity will make this seem silly from a design perspective, but in my actual use case I could use functionality like this to fit in the broader design. Also of course it's just not giving back what's specified.)

Thanks for such a versatile package!

require(flextable) # 0.7.0
#> Loading required package: flextable
require(tidyverse)
#> Loading required package: tidyverse
basetabl <- 
  iris %>% 
  slice(1:5) %>% 
  flextable() %>% 
  set_header_labels(Sepal.Width = "") %>% 
  border_remove() %>% 
  # Merge two cells:
  merge_at(i = 1, j = 1:2, part = "header") 

basetabl %>% 
  # None of these work to produce a horizontal 
  # line centered on column 2:
  hline_top(j  = 2, part = "header") %>% 
  hline_bottom(j  = 2, part = "header") %>% 
  hline_top(j  = 2, part = "body") %>% 
  # This does not help:
  fix_border_issues()

basetabl %>% 
  # Similarly can not incorporate into longer line:
  hline_bottom(j  = 2:5, part = "header") %>% 
  fix_border_issues()

basetabl %>% 
  # This "works", but adds borders across both columns 1 & 2
  # despite 1 & 2 not being merged in the body:
  hline_top(j  = 1, part = "body") %>% 
  fix_border_issues()

sessionInfo()
#> R version 4.2.0 (2022-04-22)
#> Platform: x86_64-apple-darwin17.0 (64-bit)
#> Running under: macOS Big Sur/Monterey 10.16
#> 
#> Matrix products: default
#> BLAS:   /Library/Frameworks/R.framework/Versions/4.2/Resources/lib/libRblas.0.dylib
#> LAPACK: /Library/Frameworks/R.framework/Versions/4.2/Resources/lib/libRlapack.dylib
#> 
#> locale:
#> [1] en_US.UTF-8/en_US.UTF-8/en_US.UTF-8/C/en_US.UTF-8/en_US.UTF-8
#> 
#> attached base packages:
#> [1] stats     graphics  grDevices utils     datasets  methods   base     
#> 
#> other attached packages:
#>  [1] forcats_0.5.1   stringr_1.4.0   dplyr_1.0.9     purrr_0.3.4    
#>  [5] readr_2.1.2     tidyr_1.2.0     tibble_3.1.6    ggplot2_3.3.5  
#>  [9] tidyverse_1.3.1 flextable_0.7.0
#> 
#> loaded via a namespace (and not attached):
#>  [1] tidyselect_1.1.2  xfun_0.30         haven_2.5.0       colorspace_2.0-3 
#>  [5] vctrs_0.4.1       generics_0.1.2    htmltools_0.5.2   yaml_2.3.5       
#>  [9] base64enc_0.1-3   utf8_1.2.2        rlang_1.0.2       pillar_1.7.0     
#> [13] glue_1.6.2        withr_2.5.0       DBI_1.1.2         gdtools_0.2.4    
#> [17] dbplyr_2.1.1      readxl_1.4.0      modelr_0.1.8      uuid_1.1-0       
#> [21] lifecycle_1.0.1   cellranger_1.1.0  munsell_0.5.0     gtable_0.3.0     
#> [25] rvest_1.0.2       zip_2.2.0         evaluate_0.15     knitr_1.39       
#> [29] tzdb_0.3.0        fastmap_1.1.0     fansi_1.0.3       highr_0.9        
#> [33] broom_0.8.0       Rcpp_1.0.8.3      backports_1.4.1   scales_1.2.0     
#> [37] jsonlite_1.8.0    systemfonts_1.0.4 fs_1.5.2          hms_1.1.1        
#> [41] digest_0.6.29     stringi_1.7.6     grid_4.2.0        cli_3.3.0        
#> [45] tools_4.2.0       magrittr_2.0.3    crayon_1.5.1      pkgconfig_2.0.3  
#> [49] ellipsis_0.3.2    data.table_1.14.2 xml2_1.3.3        lubridate_1.8.0  
#> [53] reprex_2.0.1      httr_1.4.2        assertthat_0.2.1  rmarkdown_2.14   
#> [57] officer_0.4.2     rstudioapi_0.13   R6_2.5.1          compiler_4.2.0

^{Created on 2022-05-16 by the reprex package (v2.0.1)}