@hackage / env-parser

env-parser is a small library for configuring programs based on information from the environment. It's goals and design are similar to that of cmdargs or optparse-applicative@ but aimed at automatically managed programs such as those that might be run via Heroku or Runit/daemontools.

env-parser intentionally sacrifices power for comprehensibility---the primary interface, Parser, implements only Applicative. This provides better runtime error messages and automatically generated static help using parser annotations. It also expresses a principle of simplicity in configuration: arbitrary uses of Monad or even Alternative can lead to opaque failures prior to a program even beginning to run.