Empties the memoised in-session cache and, optionally, the on-disk one.
What a global clear releases
Called with no source, this also drops the two cached geometry backends:
the Natural Earth sf layer held per scale (tens of megabytes at
scale = "medium") and the memoised map_data("world") tibble (about
99,000 rows per override set). Those are the largest things the package
keeps in memory, and in a long-lived process – a Shiny app or a plumber
API – this is the only way to release them. They rebuild on the next map.
Naming a source leaves geometry alone, since it is not a data source.
