class Rails::Application

def precompiled_assets(clear_cache = false)

request or test case.
boot time, but ensure we cache the list so we don't recompute it for each
Lazy-load the precompile list so we don't cause asset compilation at app 
def precompiled_assets(clear_cache = false)
  @precompiled_assets = nil if clear_cache
  @precompiled_assets ||= assets_manifest.find(config.assets.precompile).map(&:logical_path).to_set
end