When caching is enabled, this function returns a sass_file_cache() object
that sass()'s cache argument uses (by default) for caching Sass
compilation. When caching is disabled (either by setting the sass.cache
option to FALSE, NULL, or via shiny::devmode()), this function returns
NULL (effectively telling sass() to not cache by default).
sass_cache_get()When caching is enabled, then this function returns a sass_file_cache()
object that (by default) uses sass_cache_context_dir() for its directory.
The directory can also be customized by providing the sass.cache option
with either a filepath (as a string) or a full-blown sass_file_cache()
object.
sass_cache_get_dir(), sass()