Morpheus GraphQL Client with Safe Queries/Mutations

[sordina]

Spinning off from #184

• Currently we develop some Rails applications that expose a GraphQL API
• I would like to consume that API with Haskell Applications
• It would be good to have a code-gen tool that takes these schemas and generates Haskell
• There should be a way to perfrom a parameterized query/mutation in 3-phases:
  1. Codegen from the Schema (Haskell implementation of the queries/mutations/types)
  2. Codegen from the query
  • Check that the query matches the schema
  • Generate a Haskell function to perform the query with just the required params/fields
  • Generate a datatype representing the response from that query (possibly with lenses for fields) so that there are no Maybe fields for requested non-null fields.
  3. Run the query by calling the function, validating and marshaling the results.

Let me know if this is a duplicate issue!

[nalchevanidze]

Vision:

schema :: IO GQLSchema
schema = <get schema from GQL Api or doc file> 

query schema [gql|
   query GetHero ($id: Int ) {
       name
       hobby (id:)
       age
   }
]

should:

1. validate Query/Mutation
2. generate Data type Declaration GetHero:

  data GetHero = GetHero {
     _name :: Text,
     _hobby ::  Maybe Text
     _age :: Int
  }

 data GetHeroArgs = {
    _id :: Int
 }

2. generate lens instance for GetHero

3. generate Fetch instance for GetHero where

    class Fetch var a where 
      fetch :: Monad m =>  (Request -> m Value) -> var  -> m (Either Error a)

so that :

  fetchFromServer :: Request -> IO Value
  fetchFromServer req = <fetch value from server>

  fetchHero :: IO (Either Error GetHero)
  fetchHero = fetch  fetchFromServer  (GetHeroArgs { id = 2 })

@sordina , if there is something to add please let me know.

[nalchevanidze]

in release v0.2.1