no-export-side-effect.js

/**
 * Copyright 2016 The AMP HTML Authors. All Rights Reserved.
 *
 * Licensed under the Apache License, Version 2.0 (the "License");
 * you may not use this file except in compliance with the License.
 * You may obtain a copy of the License at
 *
 *      http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS-IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 */
'use strict';

module.exports = function (context) {
  return {
    ExportNamedDeclaration: function (node) {
      if (node.declaration) {
        const {declaration} = node;
        if (declaration.type === 'VariableDeclaration') {
          declaration.declarations
            .map(function (declarator) {
              return declarator.init;
            })
            .filter(function (init) {
              return init && /(?:Call|New)Expression/.test(init.type);
            })
            .forEach(function (init) {
              context.report({
                node: init,
                message: 'Cannot export side-effect',
              });
            });
        }
      }
    },
  };
};