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Include the elm source for the Haskell type specified by the proxy argument. The second argument decides which components will be included and if the generated type will be polymorphic.

Return the generated Elm code in a template haskell splice and optionally write to a Elm source file at the same time. The second argument is the Options type from Aeson library. Use include calls to build the Builder value.

Specify Elm version to generate code for

This type holds the type information we get from generics. Only the HExternal constructor is supposed to be used by the programmer to implement ToHType instances for entites that are predefined in Elm. A sample can be seen below.

Here, let `MyExtType a b` be a type which has the corresponding type, encoders and decoders predefined in Elm in a module named Lib. Here is how you can implement a ToHType instance for this type so that your other autogenerated types can have fields of type `MyExtType a b`.

instance (ToHType a, ToHType b) => ToHType (MyExtType a b) where
  toHType _ = do
    ha <- toHType (Proxy :: Proxy a)
    hb <- toHType (Proxy :: Proxy b)
    pure $
      HExternal
        (ExInfo
           (External, MyExtType)
           (Just (External, "encodeMyExtType"))
           (Just (External, "decodeMyExtType"))
           [ha, hb])

Decides which among type definiton, encoder and decoder will be included for a type. The poly config value decides wether the included type definition will be polymorphic.

Decides wether the type definition will be polymorphic.