Documentation on how to use type fields

[NorfairKing]

Using a non-monadic parser means you cannot case-match on a field to determine what to parse next.
BUT we can still use type fields like this:

data NSCheck = NSCheck
  { nsCheckDomain :: !Domain,
    nsCheckAddresses :: ![Domain]
  }
  deriving stock (Show, Eq, Generic)
  deriving (FromJSON, ToJSON) via (Autodocodec NSCheck)

instance Validity NSCheck

instance HasCodec NSCheck where
  codec =
    object "NSCheck" $
      typeField "ns" NSCheck
        <*> domainField .= nsCheckDomain
        <*> singleOrListFieldWith "value" "values" domainCodec "domains" .= nsCheckAddresses

typeField :: Text -> a -> ObjectCodec b a
typeField typeName a =
  a <$ requiredFieldWith' "type" (literalTextCodec typeName) .= const typeName

This could be documented better.

[NorfairKing]

PR welcome

[m1-s]

I do not understand this yet. So, typeField parses to NSCheck as long as type: "ns". But how can I make this parse to a different type when type contains a different value? If this is not possible, I do not get the purpose of typeField. Or is it just about ignoring the type field?

[m1-s]

Is there any other workaround, e.g. defining separate objects for each type and manually handle the case if multiple types are specified at the same time?

type: 
  type1: value1
  type2: value2

where only type1 or type2 may be specified but not both at the same time.

[NorfairKing]

@m1-s See https://hackage.haskell.org/package/autodocodec-0.2.0.3/docs/Autodocodec.html#v:eitherCodec
and https://hackage.haskell.org/package/autodocodec-0.2.0.3/docs/Autodocodec.html#v:dimapCodec