This defines a typeclass HasLgRepo m with getRepository :: m LgRepo to generalize the concrete ReaderT LgRepo m type with a HasLgRepo m => m constraint.
The motivating use case is: I'm writing a Yesod app and would like for my Handler monad stack to satisfy MonadGit LgRepo Handler. The existing implementation rather strongly forces me to use a ReaderT LgRepo Handler, but with this change it's trivial for me to define a HasLgRepo instance and get the desired MonadGit instance without having to manually specify all the MonadGit fields.
As far as I can tell, this should be fully backwards compatible, since instance Monad m => HasLgRepo (ReaderT LgRepo m) where getRepository = ask.
Somewhat new to Haskell PRs here, so if there's anything else I can do (documentation, tests) to help out, please feel free to indicate that, and I'd be happy to. Thanks for this project; it's been a big help!
jwiegley
commented
7 years ago
This defines a typeclass
HasLgRepo mwithgetRepository :: m LgRepoto generalize the concreteReaderT LgRepo mtype with aHasLgRepo m => mconstraint.The motivating use case is: I'm writing a Yesod app and would like for my
Handlermonad stack to satisfyMonadGit LgRepo Handler. The existing implementation rather strongly forces me to use aReaderT LgRepo Handler, but with this change it's trivial for me to define aHasLgRepoinstance and get the desiredMonadGitinstance without having to manually specify all theMonadGitfields.As far as I can tell, this should be fully backwards compatible, since
instance Monad m => HasLgRepo (ReaderT LgRepo m)wheregetRepository = ask.Somewhat new to Haskell PRs here, so if there's anything else I can do (documentation, tests) to help out, please feel free to indicate that, and I'd be happy to. Thanks for this project; it's been a big help!