config-check

Copperbox revision 3068.

A new project / tool for validating configurations.

A configuration is some user data represented as normal Haskell datatypes - however it is expected that configurations will already contain some errors (or at least bad smells) - after all, the configuration may originally be specified in XML, as text etc. Thus, the standard Haskell Way of developing highly refined datatypes with advanced type system features that prevent errors won't work for us, instead ConfigCheck tests instantiated simple datatypes (configurations) with Lint-like rules that identify bad or erroneous data.

The core of ConfigCheck is a static parser monad - i.e. a parser monad that doesn't consume input (it is expected to make multiple, user-directed passes over the Config datatypes). Designing the static parser monad is easy; designing a good API / set of combinators to specify rules already looks more challenging. I'm not sure the API should even look like the regular parser monad combinators Haskell programmers are used to.