serverless/lib/utils/npm-command-deferred.js

'use strict';

const path = require('path');
const fsp = require('fs').promises;

const localNpmBinPath = path.join(__dirname, '../../node_modules/npm/bin/npm-cli.js');

module.exports = fsp
  .stat(localNpmBinPath)
  .then(
    (stats) => stats.isFile(),
    (error) => {
      if (error.code === 'ENOENT') return null;
      throw error;
    }
  )
  .then((isNpmInstalledLocaly) => {
    return isNpmInstalledLocaly
      ? { command: 'node', args: [localNpmBinPath] }
      : { command: 'npm', args: [] };
  });