I use Dhall extensively now. In fact, all my typescript programs for my current employer use JSON configuration that Dhall generates (and I've tried so many tim

I use Dhall extensively now. In fact, all my typescript programs for my current employer use JSON configuration that Dhall generates (and I've tried so many times to get this to frontpage on YC, I guess I'm just not good at timing). Dhall's draw as a configuration language is that it allows you to express logic in your configuration and even call out to remote services and file handles safely. People have a gut negative reaction to this phrase even as they essentially encode non-trivial logic directly into their Chef, CircleCI, Docker-Compose and Kubernetes configs, so it's hardly a new idea. Dhall lets you write logic into your configs that otherwise would be implicit. As an example, you might define a new configuration environment with Dhall and use the types to make sure you NEVER provide production credentials, or even shared credentials. Dhall also allows you to safely call out to web services (with authentication and SSL, of course) to fill in holes or even provide non-trivial logic (it's perfectly valid to move functions around in dhall over the wire). I use this feature to map a tiny microservice that resolves Hashicorp Vault calls to AWS credentials just-in-time as I ship, and I feel very confident that it's safe because I can encode the sorts of permissions and their resolution directly into the types I'm handling. You could start using Dhall instead of JSON today for configs, and the main advantage is that you can assert values have specific types (and also provide sane loops over list fields). Dhall is actually a pretty amazing invention and I keep trying to work up the guts and time to write a typescript interpreter for it.