graphql-fields

graphql-fields

Turns GraphQLResolveInfo into a map of the requested fields. Flattens all fragments and duplicated fields into a neat object to easily see which fields were requested at any level.

Usage

Schema Type definition

const graphqlFields = require('graphql-fields');
const graphql = require('graphql')

const UserType = new graphql.GraphQLObjectType({
    name: 'User',
    fields: {
        profile: {type: new graphql.GraphQLObjectType({
          name: 'Profile',
          fields: {
            firstName: {type: graphql.GraphQLString},
            lastName: {type: graphql.GraphQLString},
            middleName: {type: graphql.GraphQLString}
          }
        }),
        email: {type: graphql.GraphQLString},
        id: {type: graphql.GraphQLID}
    }
});

module.exports = new GraphQLSchema({
    query: new GraphQLObjectType({
        name: 'Query',
        fields: () =>
            Object.assign({
                user: {
                    type: UserType,
                    resolve(root, args, context, info) {
                        console.log(
                            JSON.stringify(graphqlFields(info), null, 2);
                        );
                        ...
                    }
                }
            })
    })
})

Query

{
  user {
    ...A
    profile {
      ...B
      firstName
    }
  }
}

fragment A on User {
  ...C
  id,
  profile {
    lastName
  }
}

Fragment B on Profile {
  firstName
}

Fragment C on User {
  email,
  profile {
    middleName
  }
}

will log

{
  "profile": {
    "firstName": {},
    "lastName": {},
    "middleName": {}
  },
  "email": {},
  "id": {}
}

subfields arguments

To enable subfields arguments parsing, you'll have to provide an option object to the function. This feature is disable by default.

const graphqlFields = require('graphql-fields');
const fieldsWithSubFieldsArgs = graphqlFields(info, {}, { processArguments: true });

For each subfield w/ arguments, a __arguments property will be created. It will be an array with the following format:

[
    {
        arg1Name: {
            kind: ARG1_KIND,
            value: ARG1_VALUE,
        },
    },
    {
        arg2Name: {
            kind: ARG2_KIND,
            value: ARG2_VALUE,
        }
    }
]

The kind property is here to help differentiate value cast to strings by javascript clients, such as enum values.

Why

An underlying REST api may only return fields based on query params.

{
  user {
    profile {
      firstName
    },
    id
  }
}

should request /api/user?fields=profile,id

while

{
  user {
    email
  }
}

should request /api/user?fields=email

Implement your resolve method like so:

resolve(root, args, context, info) {
    const topLevelFields = Object.keys(graphqlFields(info));
    return fetch(`/api/user?fields=${topLevelFields.join(',')}`);
}

Tests

npm test