Advice on reproducible map_coloring?

Hi

I was wondering whether it is possible to have a replicable output with map_coloring, i.e. that is constant across calls? This is particularly useful when one is trying to use testhat snapshots.

I realize that setting minimize=TRUE avoids the call to sample(), so that is already a workaround. Should one want more colors than the strict minimum, the output seems to change each time. Do you see an easy way to add maybe a seed argument?

Thanks!

library(tmaptools)
packageVersion("tmap")
#> [1] '3.3.2'
packageVersion("tmaptools")
#> [1] '3.1.1'
library(tmap)

data(World)

color <- map_coloring(World, palette="Pastel2")
color2 <- map_coloring(World, palette="Pastel2")
all.equal(color, color2)
#> [1] "152 string mismatches"


color <- map_coloring(World, palette="Pastel2", minimize=TRUE)
color2 <- map_coloring(World, palette="Pastel2", minimize=TRUE)
all.equal(color, color2)
#> [1] TRUE

Start at the map_coloring entry point and reproduce the two examples in the issue, including the testhat snapshot use case. Investigate how sampling affects non-minimized output and determine the expected behavior for a seed argument or another reproducibility mechanism. Done means repeated calls can produce comparable output when reproducibility is requested.