invariant.js.flow

/**
 * Copyright (c) 2013-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.
 *
 * @providesModule invariant
 * @flow
 */
'use strict';

declare var __DEV__: boolean;
const validateFormat = __DEV__ ? function (format: mixed): void {} : function (format: mixed): void {
  if (format === undefined) {
    throw new Error('invariant(...): Second argument must be a string.');
  }
};
/**
 * Use invariant() to assert state which your program assumes to be true.
 *
 * Provide sprintf-style format (only %s is supported) and arguments to provide
 * information about what broke and what you were expecting.
 *
 * The invariant message will be stripped in production, but the invariant will
 * remain to ensure logic does not differ in production.
 */

function invariant(condition: mixed, format: string, ...args: Array<mixed>): void {
  validateFormat(format);

  if (!condition) {
    let error;

    if (format === undefined) {
      error = new Error('Minified exception occurred; use the non-minified dev environment ' + 'for the full error message and additional helpful warnings.');
    } else {
      let argIndex = 0;
      error = new Error(format.replace(/%s/g, () => String(args[argIndex++])));
      error.name = 'Invariant Violation';
    }

    (error: any).framesToPop = 1; // Skip invariant's own stack frame.

    throw error;
  }
}

module.exports = invariant;