group-exports.js

'use strict';

var _docsUrl = require('../docsUrl');

var _docsUrl2 = _interopRequireDefault(_docsUrl);

function _interopRequireDefault(obj) { return obj && obj.__esModule ? obj : { default: obj }; }

const meta = {
  docs: {
    url: (0, _docsUrl2.default)('group-exports')
  }
  /* eslint-disable max-len */
};const errors = {
  ExportNamedDeclaration: 'Multiple named export declarations; consolidate all named exports into a single export declaration',
  AssignmentExpression: 'Multiple CommonJS exports; consolidate all exports into a single assignment to `module.exports`'
  /* eslint-enable max-len */

  /**
   * Returns an array with names of the properties in the accessor chain for MemberExpression nodes
   *
   * Example:
   *
   * `module.exports = {}` => ['module', 'exports']
   * `module.exports.property = true` => ['module', 'exports', 'property']
   *
   * @param     {Node}    node    AST Node (MemberExpression)
   * @return    {Array}           Array with the property names in the chain
   * @private
   */
};function accessorChain(node) {
  const chain = [];

  do {
    chain.unshift(node.property.name);

    if (node.object.type === 'Identifier') {
      chain.unshift(node.object.name);
      break;
    }

    node = node.object;
  } while (node.type === 'MemberExpression');

  return chain;
}

function create(context) {
  const nodes = {
    modules: new Set(),
    commonjs: new Set()
  };

  return {
    ExportNamedDeclaration(node) {
      nodes.modules.add(node);
    },

    AssignmentExpression(node) {
      if (node.left.type !== 'MemberExpression') {
        return;
      }

      const chain = accessorChain(node.left);

      // Assignments to module.exports
      // Deeper assignments are ignored since they just modify what's already being exported
      // (ie. module.exports.exported.prop = true is ignored)
      if (chain[0] === 'module' && chain[1] === 'exports' && chain.length <= 3) {
        nodes.commonjs.add(node);
        return;
      }

      // Assignments to exports (exports.* = *)
      if (chain[0] === 'exports' && chain.length === 2) {
        nodes.commonjs.add(node);
        return;
      }
    },

    'Program:exit': function onExit() {
      // Report multiple `export` declarations (ES2015 modules)
      if (nodes.modules.size > 1) {
        nodes.modules.forEach(node => {
          context.report({
            node,
            message: errors[node.type]
          });
        });
      }

      // Report multiple `module.exports` assignments (CommonJS)
      if (nodes.commonjs.size > 1) {
        nodes.commonjs.forEach(node => {
          context.report({
            node,
            message: errors[node.type]
          });
        });
      }
    }
  };
}

module.exports = {
  meta,
  create
};
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