The API allows overriding file system operations by injecting a different implementation of FileSystem. That allows for in-memory file systems and similar concepts.

The only thing that uses Node's fs module directly is glob. This is only used if you don't lint a project, but still it's very inconsistent. This inconsistency also causes duplicate file system operations by using a separate cache.

One possibility is to provide a Proxy for the certain cache options of glob. Behind the scenes this proxy does the file system access and caching using CachedFileSystem. If glob finds a value in the cache, it doesn't try to access the real file system.