Get object type from FieldNode in a GraphQL validator

I'm writing a authorization component to validate GraphQL queries.

Using the ValidationContextobject I manage to get the operation type (mutation/query), operation name and the non-scalar field names contained in the query.

What I need is to get the GraphQL type of these non-scalar fields.

Here is the code I'm using for the validator (using Typescript):

let entitiesArray:Array<string> = new Array<string>()

function getRecursiveSelectionSetNodes (selSetNode:SelectionSetNode) {
  selSetNode.selections.forEach ((node:FieldNode, index, array) => {
    if (node.selectionSet) {
      entitiesArray.push(node.name.value) // I could push the whole node, and make an array of nodes if necessary 
      getRecursiveSelectionSetNodes (node.selectionSet)
    }
  })
}

export const authorizeQuery = function authorizeQuery (context: ValidationContext): any {

  let opNode:OperationDefinitionNode = getOperationAST(context.getDocument())

  let opType = opNode.operation
  console.log ('_________________ AUTH OPERATION TYPE: ', opType)

  let opFieldNode:FieldNode = <FieldNode>opNode.selectionSet.selections[0]
  let opName = opFieldNode.name.value

  console.log ('_________________ AUTH OPERATION NAME: ', opName)

    let selSetUser:SelectionSetNode = opFieldNode.selectionSet
  // Selected fields by the user
  // Here, first-level nodes will be objects requested by the query
  // The nodes without a nested "SelectionSet" node will be scalar
  // Nodes with a nested "SelectionSet" are non-scalar that need to be checked

  getRecursiveSelectionSetNodes (selSetUser)

  console.log ('_________________ AUTH ENTITIES: ', JSON.stringify(entitiesArray))

  return []

}

This code returns the field names, not the type, so I need to map the field name "users" with the graphQL type "User[]", and so on, so I can perform authorization based on the graphql type being requested.

Any ideas?

via Carlos Delgado