serverless/test/unit/lib/utils/fs/safeMoveFile.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/safeMoveFile');

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 fse.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;
    });
  });
});