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

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

/**
 * 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.
 *
 * @flow
 */

import type { ValidationContext } from '../index';
import { GraphQLError } from '../../error';


export function duplicateOperationNameMessage(operationName: string): string {
  return `There can be only one operation named "${operationName}".`;
}

/**
 * Unique operation names
 *
 * A GraphQL document is only valid if all defined operations have unique names.
 */
export function UniqueOperationNames(context: ValidationContext): any {
  const knownOperationNames = Object.create(null);
  return {
    OperationDefinition(node) {
      const operationName = node.name;
      if (operationName) {
        if (knownOperationNames[operationName.value]) {
          context.reportError(new GraphQLError(
            duplicateOperationNameMessage(operationName.value),
            [ knownOperationNames[operationName.value], operationName ]
          ));
        } else {
          knownOperationNames[operationName.value] = operationName;
        }
      }
      return false;
    },
    FragmentDefinition: () => false,
  };
}