nedb/test_lac/loadAndCrash.test.js

/* eslint-env mocha */
/* global DEBUG */
/**
 * Load and modify part of fs to ensure writeFile will crash after writing 5000 bytes
 */
const fs = require('fs')

function rethrow () {
  // Only enable in debug mode. A backtrace uses ~1000 bytes of heap space and
  // is fairly slow to generate.
  if (DEBUG) {
    const backtrace = new Error()
    return function (err) {
      if (err) {
        backtrace.stack = err.name + ': ' + err.message +
          backtrace.stack.substr(backtrace.name.length)
        throw backtrace
      }
    }
  }

  return function (err) {
    if (err) {
      throw err // Forgot a callback but don't know where? Use NODE_DEBUG=fs
    }
  }
}

function maybeCallback (cb) {
  return typeof cb === 'function' ? cb : rethrow()
}

function isFd (path) {
  return (path >>> 0) === path
}

function assertEncoding (encoding) {
  if (encoding && !Buffer.isEncoding(encoding)) {
    throw new Error('Unknown encoding: ' + encoding)
  }
}

let onePassDone = false

function writeAll (fd, isUserFd, buffer, offset, length, position, callback_) {
  const callback = maybeCallback(arguments[arguments.length - 1])

  if (onePassDone) { process.exit(1) } // Crash on purpose before rewrite done
  const l = Math.min(5000, length) // Force write by chunks of 5000 bytes to ensure data will be incomplete on crash

  // write(fd, buffer, offset, length, position, callback)
  fs.write(fd, buffer, offset, l, position, function (writeErr, written) {
    if (writeErr) {
      if (isUserFd) {
        if (callback) callback(writeErr)
      } else {
        fs.close(fd, function () {
          if (callback) callback(writeErr)
        })
      }
    } else {
      onePassDone = true
      if (written === length) {
        if (isUserFd) {
          if (callback) callback(null)
        } else {
          fs.close(fd, callback)
        }
      } else {
        offset += written
        length -= written
        if (position !== null) {
          position += written
        }
        writeAll(fd, isUserFd, buffer, offset, length, position, callback)
      }
    }
  })
}

fs.writeFile = function (path, data, options, callback_) {
  const callback = maybeCallback(arguments[arguments.length - 1])

  if (!options || typeof options === 'function') {
    options = { encoding: 'utf8', mode: 438, flag: 'w' } // Mode 438 == 0o666 (compatibility with older Node releases)
  } else if (typeof options === 'string') {
    options = { encoding: options, mode: 438, flag: 'w' } // Mode 438 == 0o666 (compatibility with older Node releases)
  } else if (typeof options !== 'object') {
    throw new Error(`throwOptionsError${options}`)
  }

  assertEncoding(options.encoding)

  const flag = options.flag || 'w'

  if (isFd(path)) {
    writeFd(path, true)
    return
  }

  fs.open(path, flag, options.mode, function (openErr, fd) {
    if (openErr) {
      if (callback) callback(openErr)
    } else {
      writeFd(fd, false)
    }
  })

  function writeFd (fd, isUserFd) {
    const buffer = (data instanceof Buffer) ? data : Buffer.from('' + data, options.encoding || 'utf8')
    const position = /a/.test(flag) ? null : 0

    writeAll(fd, isUserFd, buffer, 0, buffer.length, position, callback)
  }
}

// End of fs modification
const Nedb = require('../lib/datastore.js')
const db = new Nedb({ filename: 'workspace/lac.db' })

db.loadDatabase()