No way to get requested fields of the object inside `resolve`

Let’s say I have a Database with User entity with a lot of fields:

var Sequelize = require('sequelize');
var sequelize = new Sequelize('sqlite://database.db');

var User = sequelize.define('User', {
  name: Sequelize.STRING,
  email: Sequelize.STRING,
  otherField: Sequelize.STRING,
});

And I have a GraphQL:

var queryType = new GraphQLObjectType({
  name: 'Query',
  fields: () => ({
    user: {
      type: userType,
      args: { id: { type: GraphQLID } },
      resolve: (_, {id}) => User.findById(id)
    },
    users: {
      type: new GraphQLList(userType),
      resolve: (source, args) => {
        User.all(); // How to get the requested fields?
        //User.all({ attributes: args._requestedFields });
      }
    },
  })
});

And I do a GraphQL query to get name of all users

 curl -s -X POST http://localhost:8080/api/graph -d '{ users { name } }' | jq '.'

I don’t want to fetch all the fields from the database. I want to know what fields to fetch…

Is there any way to get a list of fields that were requested in resolve method?

[benjie]

For anyone else who lands here; fieldASTs was renamed to fieldNodes in v0.8.0

[devknoll]

Here’s one idea… The 4th argument to resolve is the AST for the field. In your simple example, you could get the fields with something like:

resolve: (source, args, root, ast) => {
  var args = ast.selectionSet.selections.map(selection => selection.name.value);
  User.all({ attributes: args });
}

That would work, as long as you didn’t have any fragments/spreads/etc. For more advanced cases, you could probably use the AST visitor utils. There’s also a curious // TODO: provide all fieldASTs, not just the first field for that param too…

I believe that I heard that Facebook optimizes things like this internally, so hopefully Lee will show up and drop some wisdom 😄