@dillonkearns/elm-graphql/examples/src/subscription/node_modules/graphql/validation/rules/SingleFieldSubscriptions.js

<img src="https://cdn.jsdelivr.net/gh/martimatix/logo-graphqelm/logo.svg" alt="dillonearns/elm-graphql logo" width="40%" align="right">

'use strict';

Object.defineProperty(exports, "__esModule", {
  value: true
});
exports.singleFieldOnlyMessage = singleFieldOnlyMessage;
exports.SingleFieldSubscriptions = SingleFieldSubscriptions;

var _error = require('../../error');

/**
 * Copyright (c) 2015-present, Facebook, Inc.
 *
 * This source code is licensed under the MIT license found in the
 * LICENSE file in the root directory of this source tree.
 *
 * 
 */

function singleFieldOnlyMessage(name) {
  return (name ? 'Subscription "' + name + '" ' : 'Anonymous Subscription ') + 'must select only one top level field.';
}

/**
 * Subscriptions must only include one field.
 *
 * A GraphQL subscription is valid only if it contains a single root field.
 */
function SingleFieldSubscriptions(context) {
  return {
    OperationDefinition: function OperationDefinition(node) {
      if (node.operation === 'subscription') {
        if (node.selectionSet.selections.length !== 1) {
          context.reportError(new _error.GraphQLError(singleFieldOnlyMessage(node.name && node.name.value), node.selectionSet.selections.slice(1)));
        }
      }
    }
  };
}