graphql/validation/rules/UniqueOperationTypesRule.mjs

import { GraphQLError } from "../../error/GraphQLError.mjs";

/**
 * Unique operation types
 *
 * A GraphQL document is only valid if it has only one type per operation.
 */
export function UniqueOperationTypesRule(context) {
  var schema = context.getSchema();
  var definedOperationTypes = Object.create(null);
  var existingOperationTypes = schema ? {
    query: schema.getQueryType(),
    mutation: schema.getMutationType(),
    subscription: schema.getSubscriptionType()
  } : {};
  return {
    SchemaDefinition: checkOperationTypes,
    SchemaExtension: checkOperationTypes
  };

  function checkOperationTypes(node) {
    var _node$operationTypes;

    // istanbul ignore next (See: 'https://github.com/graphql/graphql-js/issues/2203')
    var operationTypesNodes = (_node$operationTypes = node.operationTypes) !== null && _node$operationTypes !== void 0 ? _node$operationTypes : [];

    for (var _i2 = 0; _i2 < operationTypesNodes.length; _i2++) {
      var operationType = operationTypesNodes[_i2];
      var operation = operationType.operation;
      var alreadyDefinedOperationType = definedOperationTypes[operation];

      if (existingOperationTypes[operation]) {
        context.reportError(new GraphQLError("Type for ".concat(operation, " already defined in the schema. It cannot be redefined."), operationType));
      } else if (alreadyDefinedOperationType) {
        context.reportError(new GraphQLError("There can be only one ".concat(operation, " type in schema."), [alreadyDefinedOperationType, operationType]));
      } else {
        definedOperationTypes[operation] = operationType;
      }
    }

    return false;
  }
}