serverless/test/unit/lib/utils/fs/safe-move-file.test.js

'use strict'

const fse = require('fs-extra')
const sinon = require('sinon')
const chai = require('chai')
const provisionTempDir = require('@serverless/test/provision-tmp-dir')
const { join } = require('path')
const { expect } = require('chai')
const fsp = require('fs').promises
const fs = require('fs')
const sinonChai = require('sinon-chai')
const safeMoveFile = require('../../../../../lib/utils/fs/safe-move-file')

chai.use(sinonChai)

/**
 * Returns and Error object that resembles the EXDEV errors that are thrown
 * when you try to rename across device boundaries.
 *
 * @returns an Error object that resembles the EXDEV errors are thrown
 */
const createFakeExDevError = () => {
  // Properties captured by using fs.renameSync in the Node v12.20.1 REPL
  const fakeCrossDeviceError = new Error(
    "Error: EXDEV: cross-device link not permitted, rename '/foo/bar' -> '/bar/baz'",
  )
  // This is the important property that safeMoveFile looks for
  // to fallback to copy then rename behaviour
  fakeCrossDeviceError.code = 'EXDEV'

  // These other properties aren't used but it doesn't hurt to have an accurate error object
  fakeCrossDeviceError.errno = -18
  fakeCrossDeviceError.syscall = 'rename'
  fakeCrossDeviceError.path = '/foo/bar'
  fakeCrossDeviceError.dest = '/bar/baz'
  return fakeCrossDeviceError
}

/**
 * The name of the file that will be moved
 */
const artifactName = 'foo-bar.zip'

describe('test/unit/lib/utils/fs/safeMoveFile.test.js', () => {
  let sourceDir
  let destinationDir
  let sourceFile
  let destinationFile

  let renameStub

  beforeEach(async () => {
    sourceDir = await provisionTempDir()
    destinationDir = await provisionTempDir()
    sourceFile = join(sourceDir, artifactName)
    destinationFile = join(destinationDir, artifactName)

    renameStub = sinon.stub(fsp, 'rename')
    // Allow the fs calls to act as normal until we want to force the rename to fail
    renameStub.callThrough()

    // Write a test file to rename
    await fsp.writeFile(sourceFile, 'source data')
  })

  afterEach(async () => {
    // Clean up test directories after each test so they don't interfere with each other
    await fse.remove(destinationDir)
    await fse.remove(sourceDir)
    // Reset stubbed methods
    fsp.rename.restore()
  })

  /**
   * Run the test suite with the provided post assertion function.
   * The post assertion function will be called after each test scenario is executed
   * so that the test scenarios can be reused.
   *
   * @param {*} postAssertion the function that is called after every test scenario
   */
  const runTestScenariosWithPostAssertion = (postAssertion) => {
    describe('when file at target path does not exist', () => {
      it('should move file to target destination', async () => {
        await safeMoveFile(sourceFile, destinationFile)

        const sourceExists = fs.existsSync(sourceFile)
        const destinationExists = fs.existsSync(destinationFile)

        expect(sourceExists).to.be.false
        expect(destinationExists).to.be.true

        postAssertion()
      })
    })

    describe('when file at target path already exists', () => {
      beforeEach(async () => {
        // Create an existing file that is at the destination
        fse.ensureFileSync(destinationFile)
        fse.writeFileSync(destinationFile, 'existing destination data')
      })

      it('should overwrite the file at the target destination', async () => {
        await safeMoveFile(sourceFile, destinationFile)

        // Check that the file was actually overwritten
        const cachedData = fse.readFileSync(destinationFile).toString()
        expect(cachedData).not.to.eq('existing destination data')

        const sourceExists = await fs.existsSync(sourceFile)
        expect(sourceExists).to.be.false

        postAssertion()
      })
    })
  }

  describe('when file is moved in context of same device', () => {
    runTestScenariosWithPostAssertion(() => {
      // Happy path: Only rename is called
      expect(renameStub).to.have.be.calledOnce
    })
  })

  describe('when file is moved to different device', () => {
    beforeEach(async () => {
      const error = createFakeExDevError()
      renameStub.onFirstCall().rejects(error)
    })

    runTestScenariosWithPostAssertion(() => {
      // Rename is called twice because the first call will fail due to the cross device rename
      // The second call is across the same device
      expect(renameStub).to.have.been.calledTwice
    })
  })
})