Specifies whether caching is used with sass, and where on the file system the cached data should be stored. Used with sass.

  cache = getOption("sass.cache", !interactive()),
  cache_dir = getOption("sass.cache_dir", tempdir())



Logical value indicating whether caching is performed. If no value is provided, the R option sass.cache is consulted; if the option is not set, then caching is performed only if the R session is not interactive.


The directory which will be used to store cache files. If no value is provided, the R option sass.cache_dir is consulted; if the option is not set, then tempdir is used. Note that this means that caches will not persist beyond the current R session by default, since tempdir() is unique to each session.


If caching is enabled, sass() will attempt to bypass the compilation process by reusing output from previous sass() calls that used equivalent inputs. This mechanism works by using a hashing algorithm to derive a cache key from each sass() call's input and options arguments. If a file named CACHE_KEY.sasscache.css exists within the cache directory, its contents are used instead of performing the compilation. If the file does not exist, then compilation is performed and usual and the results are stored at that file path for next time.

If a file that is included using sass_file changes on disk (i.e. its last-modified time changes), its previous cache entries will effectively be invalidated (not removed from disk, but they'll no longer be matched). However, if a file imported using sass_file itself imports other sass files using @import, changes to those files are invisible to the cache and you will end up with stale results.

If a cache directory is explicitly specified (either via the cache_dir argument or via the sass.cache_dir R option), note that this package does not do any cleanup of that directory. If disk space is a concern, you will need to delete older entries from that directory yourself.


# Very slow to compile fib_sass <- "@function fib($x) { @if $x <= 1 { @return $x } @return fib($x - 2) + fib($x - 1); } body { width: fib(27); }" # Use a custom cache dir for the purposes of this example. Normally, # you'd want to set the caching behavior using options(). temp_cache_dir <- tempfile("sass_cache_dir") dir.create(temp_cache_dir) cache_opts <- sass_cache_options(TRUE, cache_dir = temp_cache_dir) # The first time this runs it will be very slow system.time(sass(fib_sass, cache_options = cache_opts))
#> user system elapsed #> 1.714 0.004 1.720
# But on subsequent calls, it should be very fast system.time(sass(fib_sass, cache_options = cache_opts))
#> user system elapsed #> 0.001 0.000 0.001