[FR] skipEmptyColumn should keep empty named columns

[JanMarvin]

It was requested that openxlsx2 could keep empty columns with wb_to_df(skipEmptyColumn = TRUE) so that only columns which are NAs are kept. This should be doable, we only have to move the output creating part of wb_to_df() behind the skipEmtpyColumn part.

library(openxlsx2)

# feature request skipEmptyCols skips should keep named empty columns

# removes empty column Species
# dat <- wb_to_df(wb, skipEmptyCols = TRUE)

## initialize empty cells
na_mat <- matrix(NA, nrow = 22, ncol = 7)

## create artificial data with empty column
dat    <- iris[1:20,]
dat$Species <- NA

## create the workbook
wb <- wb_workbook()$
  add_worksheet()$
  add_data(x = na_mat, colNames = FALSE)$
  add_data(x = dat)


# workaround
header <- wb_to_df(wb, rows = 1, colNames = FALSE, skipEmptyCols = TRUE)
dat <- read_xlsx(wb, cols = names(header))

head(dat)
#>   Sepal.Length Sepal.Width Petal.Length Petal.Width Species
#> 2          5.1         3.5          1.4         0.2      NA
#> 3          4.9         3.0          1.4         0.2      NA
#> 4          4.7         3.2          1.3         0.2      NA
#> 5          4.6         3.1          1.5         0.2      NA
#> 6          5.0         3.6          1.4         0.2      NA
#> 7          5.4         3.9          1.7         0.4      NA