Add wk_is_empty() handler / utility?

[anthonynorth]

Could we add an "is empty" handler or utility wrapper over wk_count()? The following works, but may be inefficient, particularly for WKT.

wk_is_empty <- function(handleable) {
  wk::wk_count(handleable)$n_coord == 0L
}

AFAIK, wk_meta() (which should generally be faster?) cannot currently be used for this purpose, since it doesn't read any coordinates. wk_meta() gives a correct size for POINT EMPTY, MULTIPOINT EMPTY etc, but not for geometry collections.

# if wk_meta is modified to read at least one non-empty coord
wk_is_empty2 <- function(handleable) {
  size <- wk::wk_meta(handleable)$size
  !is.na(size) & size == 0L
}

# empty
wk::wk_meta(wk::wkt("GEOMETRYCOLLECTION (POINT EMPTY)"))
#>   geometry_type size has_z has_m srid precision
#> 1             7   NA FALSE FALSE   NA         0
wk::wk_count(wk::wkt("GEOMETRYCOLLECTION (POINT EMPTY)"))
#>   n_geom n_ring n_coord
#> 1      2      0       0
# not empty
wk::wk_meta(wk::wkt("GEOMETRYCOLLECTION (POINT (1 1))"))
#>   geometry_type size has_z has_m srid precision
#> 1             7   NA FALSE FALSE   NA         0
wk::wk_count(wk::wkt("GEOMETRYCOLLECTION (POINT (1 1))"))
#>   n_geom n_ring n_coord
#> 1      2      0       1

wk::wk_meta(wk::wkt("POINT EMPTY"))
#>   geometry_type size has_z has_m srid precision
#> 1             1    0 FALSE FALSE   NA         0
wk::wk_meta(wk::wkt("MULTIPOINT EMPTY"))
#>   geometry_type size has_z has_m srid precision
#> 1             4    0 FALSE FALSE   NA         0
wk::wk_meta(wk::wkt("LINESTRING EMPTY"))
#>   geometry_type size has_z has_m srid precision
#> 1             2    0 FALSE FALSE   NA         0
wk::wk_meta(wk::wkt("MULTILINESTRING EMPTY"))
#>   geometry_type size has_z has_m srid precision
#> 1             5    0 FALSE FALSE   NA         0
wk::wk_meta(wk::wkt("POLYGON EMPTY"))
#>   geometry_type size has_z has_m srid precision
#> 1             3    0 FALSE FALSE   NA         0
wk::wk_meta(wk::wkt("MULTIPOLYGON EMPTY"))
#>   geometry_type size has_z has_m srid precision
#> 1             6    0 FALSE FALSE   NA         0

^{Created on 2023-10-03 with reprex v2.0.2}

edit: clarity