serverless/lib/utils/standalone-patch.js

'use strict';

// Workaround 'pkg' bug: https://github.com/zeit/pkg/issues/420
// Copying files from snapshot via `fs.copyFileSync` crashes with ENOENT
// Overriding copyFileSync with primitive alternative

const fs = require('fs');

if (!fs.copyFile) return;

const path = require('path');

const originalCopyFile = fs.copyFile;
const originalCopyFileSync = fs.copyFileSync;

fs.copyFile = function copyFile(src, dest, flags, callback) {
  if (!path.resolve(src).startsWith('/snapshot/')) {
    originalCopyFile(src, dest, flags, callback);
    return;
  }
  if (typeof flags === 'function') {
    callback = flags;
    flags = 0;
  } else if (typeof callback !== 'function') {
    throw new TypeError('Callback must be a function');
  }

  fs.readFile(src, (readError, content) => {
    if (readError) {
      callback(readError);
      return;
    }
    if (flags & fs.constants.COPYFILE_EXCL) {
      fs.stat(dest, statError => {
        if (!statError) {
          callback(Object.assign(new Error('File already exists'), { code: 'EEXIST' }));
          return;
        }
        if (statError.code !== 'ENOENT') {
          callback(statError);
          return;
        }
        fs.writeFile(dest, content, callback);
      });
    } else {
      fs.writeFile(dest, content, callback);
    }
  });
};

fs.copyFileSync = function copyFileSync(src, dest, flags) {
  if (!path.resolve(src).startsWith('/snapshot/')) {
    originalCopyFileSync(src, dest, flags);
    return;
  }
  const content = fs.readFileSync(src);
  if (flags & fs.constants.COPYFILE_EXCL) {
    try {
      fs.statSync(dest);
    } catch (statError) {
      if (statError.code !== 'ENOENT') throw statError;
      fs.writeFileSync(dest, content);
      return;
    }
    throw Object.assign(new Error('File already exists'), { code: 'EEXIST' });
  }
  fs.writeFileSync(dest, content);
};

if (!fs.promises) return;

const { promisify } = require('util');

fs.promises.copyFile = promisify(fs.copyFile);