From/ToDhall no longer takes InterpretOptions argument

[akrmn]

Coming from aeson, I wanted to define FromDhall instances for my types which built on GHC.Generics but with tweaked options (say, drop prefixes). Ideally, I would write something like

{- dhall type: { Name : Text, Email : Text }
-}
data Person = Person
  { personName :: Text
  , personEmail :: Text
  } 
  deriving (Generic)

instance FromDhall Person where
  autoWith = genericAutoWith defaultInterpretOptions 
    { fieldModifier = Text.drop (Text.length "person") 
    }

The problem with this is that autoWith itself takes a InterpretOptions argument, which is set to defaultInterpretOptions by auto, the most common entry point. This means that the only way to enforce a canonical FromDhall instance for a type is by ignoring the argument to autoWith, which is confusing for callers. In practice, this PR is only reflecting in the types the fact that all instances of FromDhall and ToDhall necessarily ignore the InterpretOptions, either because they don't need it or because they overwrite it. The only field that was actually used, inputNormalizer, was kept as an input.

• InterpretOptions split into smaller InterpretOptions record and InputNormalizer newtype.
• FromDhall method autoWith and ToDhall method injectWith no longer take InterpretOptions arguments, instead, they take an InputNormalizer, since the only field that instances of these classes ever used was inputNormalizer (only used by instances for (->)).
• GenericFromDhall method genericAutoWithNormalizer (renamed from genericAutoWith) and GenericToDhall method genericToDhallWithNormalizer(renamed from genericToDhallWith) now take an InputNormalizer in addition to an InterpretOptions.

[Gabriella439]

Yeah, I agree that the aeson way of doing things makes more sense! Thank you for fixing this 🙂

[akrmn]

Awesome! Thanks a lot, Gabriel

[Gabriella439]

@akrmn: You're welcome! 🙂

[patrickmn]

@akrmn Catching a codebase that used a custom fieldModifier up with this change, and it does not appear that defaultInputNormalizer is exported, which I need for autoWith (right?)

[Gabriella439]

@patrickmn: Yeah, it's not currently exported, but it's not hard to locally define:

https://hackage.haskell.org/package/dhall-1.31.0/docs/src/Dhall.html#defaultInputNormalizer

[patrickmn]

@Gabriel439 for that I'd need the newtype to be exported, right?

Or, in other words, how would I externally make an instance with a custom field modifier? (I can't use DerivingVia.)

[Gabriella439]

@patrickmn: The newtype is exported: https://hackage.haskell.org/package/dhall-1.31.0/docs/Dhall-Core.html#t:ReifiedNormalizer

[Gabriella439]

@patrickmn: Oh sorry, wrong newtype. Never mind

[Gabriella439]

@patrickmn: I have a fix up here: #1727

I can also cut a 1.31.1 point release for this

[patrickmn]

Awesome, will finish my port as soon as it's merged just in case there's anything else pre-1.31.1.

[patrickmn]

All good. Thank you!

[Gabriella439]

@patrickmn: You're welcome! 🙂