Reflexive relation types, fixes for #113 and #124

[michaeldgraham]

Fixes

• Don't drop non-Query/Mutation resolvers passed into makeAugmentedExecutableSchema Don't drop non-Query/Mutation resolvers passed into makeAugmentedExecutableSchema #113

• Basic schema with non nullable property gives error when calling mutation Basic schema with non nullable property gives error when calling mutation #124

• Error when adding directive declarative to SDL Error when adding directive declarative to SDL #116

Features:

Reflexive Relation API

The following FriendOf relation type is reflexive in the sense that it comes from and goes to the same type. There is now support in the generated Query and Mutation API for reflexive relation types.

type User implements Person {
  ...
  rated(rating: Int): [Rated]
  friends(since: Int): [FriendOf]
}

# Reflexive relation type
type FriendOf {
  from: User
  since: Int
  to: User
}

type Rated {
  from: User
  rating: Int
  to: Movie
}

Given the above SDL format (what you write), the following SDL is generated as a result of the schema augmentation process (augmentSchema or makeAugmentedSchema). The since argument on the friends is distributed over the directed fields, from and to.

type User implements Person {
  userId: ID!
  name: String
  rated(rating: Int): [_UserRated]
  friends: _UserFriendsDirections
}

type _UserFriendsDirections {
  from(since: Int): [_UserFriends]
  to(since: Int): [_UserFriends]
}

type _UserFriends {
  since: Int
  User: User
}

This results in support for the following selection set format:

User {
  userId
  name
  friends {
    from(since: 1) {
      since
      User {
        name
      }
    }
    to(since: 2) {
      since
      User {
        name
      }
    }
  }
}

Tests

The following tests have been added in cypherTest.js for the reflexive relation type API:

• Add relationship mutation with relationship property (reflexive)
• Remove relationship mutation (reflexive)
• query reflexive relation nested in non-reflexive relation
• query non-reflexive relation nested in reflexive relation
• query relation type with argument
• query reflexive relation type with arguments

Other

This PR also introduces a new translate.js file, from which helpers are exported and used in index.js, refactoring the recursive GraphQL to Cypher translation process.