How to use the yarn.lock function in yarn

const fileList = [
    'package.json',
    'backend/package.json'
  ]

  const files = await getFiles({ installationId: '123', fullName: 'owner/repo', files: fileList, log })
  // returns an Object with the 5 file types
  expect(Object.keys(files)).toHaveLength(5)
  // The Object has 2 files at the `package.json` key
  expect(files['package.json']).toHaveLength(2)
  expect(files['package.json'][0].path).toEqual('package.json')
  expect(files['package.json'][0].content).toEqual('eyJuYW1lIjoidGVzdCJ9')
  expect(files['package.json'][1].path).toEqual('backend/package.json')
  expect(files['package.json'][1].content).toEqual('eyJuYW1lIjoidGVzdCJ9')
  expect(files['yarn.lock']).toHaveLength(2)
})

async function getInvalidPackages() {
  const packages = (await new Project(__dirname).getPackages())
    .filter(p => p.scripts.build) // Only packages that have a build target
    .filter(p => (isPf3 ? p.location.indexOf('patternfly-3') > 0 || commonPackages.indexOf(p.name) >= 0 : true)) // Based off argv
    .filter(p => (isPf4 ? p.location.indexOf('patternfly-4') > 0 || commonPackages.indexOf(p.name) >= 0 : true)); // Based off argv

  for (let p of packages) {
    p.hash = hashPackageSrc(p.location, p.name);
    p.valid = cache && cache[p.name] === p.hash;
    if (p.valid) {
      console.info('Skipping', p.name, '(already built).');
    }
  }

  // Invalidate everything if any deps change.
  if (cache['yarn.lock'] !== yarnLockHash) {
    return packages;
  }

  return packages.filter(p => !p.valid);
}

Cache.prototype.load = async function() {
  // This should never throw, if it does, let it fail the build
  const lockfile = await readFile("yarn.lock", "utf-8");
  const lockfileHash = hashString(lockfile);
  this.updated.checksums["yarn.lock"] = lockfileHash;

  try {
    const manifest = await readFile(this.manifest, "utf-8");
    const { version, checksums, files } = JSON.parse(manifest);

    // Ignore the cache if the version changed
    assert.equal(this.version, version);

    assert.ok(typeof checksums === "object");
    // If yarn.lock changed, rebuild everything
    assert.equal(lockfileHash, checksums["yarn.lock"]);
    this.checksums = checksums;

    assert.ok(typeof files === "object");
    this.files = files;

Cache.prototype.load = async function() {
  // This should never throw, if it does, let it fail the build
  const lockfile = await readFile("yarn.lock", "utf-8");
  const lockfileHash = hashString(lockfile);
  this.updated.checksums["yarn.lock"] = lockfileHash;

  try {
    const manifest = await readFile(this.manifest, "utf-8");
    const { version, checksums, files } = JSON.parse(manifest);

    // Ignore the cache if the version changed
    assert.equal(this.version, version);

    assert.ok(typeof checksums === "object");
    // If yarn.lock changed, rebuild everything
    assert.equal(lockfileHash, checksums["yarn.lock"]);
    this.checksums = checksums;

    assert.ok(typeof files === "object");
    this.files = files;

    for (const files of Object.values(this.files)) {
      assert.ok(Array.isArray(files));
    }
  } catch (err) {
    this.checksums = {};
    this.files = {};
  }
};

const createLockfileCommits = async ({ commits, repoDoc, installationId, commitMessageTemplates, transforms, owner, repoName, branch }, log) => {
  const ghqueue = githubQueue(installationId)
  const lockfileCommits = []

  // we need to iterate over every changed package file, not every package file commit
  // we reverse because we want the most recent commit with the all the changes to the file (the last one)
  // we clone because we don’t actually want to do the commits backwards
  const dedupedCommits = _.uniqBy(_.clone(commits).reverse(), commit => commit.path)
  // For yarn workspaces, we have to send the updated packages object (after applying all the update commits).
  // So we need to iterate over all commits, replace all updated packages in the packages object,
  // send all of them (old and updated together) to the exec server, tell it in which directory to run
  // yarn install, and get the old yarn lock from that dir as well
  let updatedPackages = _.clone(repoDoc.packages)
  let workspaceRootsToUpdate = []
  let packageJsonPathsWithWorkspaceDefinitions = []
  const isYarn = repoDoc.files['yarn.lock'].length > 0
  if (isYarn) {
    packageJsonPathsWithWorkspaceDefinitions = Object.keys(repoDoc.packages).filter(path => {
      const packageJson = repoDoc.packages[path]
      const workspaceDefinition = packageJson.workspaces
      // either has simple workspace definition…
      if (workspaceDefinition && workspaceDefinition.length > 0) {
        return path
      }
      // or a complex definition
      if (workspaceDefinition && workspaceDefinition.packages && workspaceDefinition.packages.length > 0) {
        return path
      }
    })
  }
  const execTokens = await getExecTokens({
    installationId,

.reply(200, {
        path: 'package-lock.json',
        name: 'package-lock.json',
        content: encodePkg({ who: 'cares' })
      })
      .get('/repos/finnp/test')
      .reply(200, {
        default_branch: 'custom'
      })

    const newJob = await createInitialBranch({ repositoryId: 44 })
    expect(newJob).toBeFalsy()
    const repodoc = await repositories.get('44')
    expect(repodoc.files['package.json']).not.toHaveLength(0)
    expect(repodoc.files['package-lock.json']).not.toHaveLength(0)
    expect(repodoc.files['yarn.lock']).toHaveLength(0)
    expect(repodoc.enabled).toBeTruthy()
  })

function excludeLockFiles(files: Files): Files {
  const newFiles = files;
  if (newFiles['package-lock.json']) {
    delete newFiles['package-lock.json'];
  }
  if (newFiles['yarn.lock']) {
    delete newFiles['yarn.lock'];
  }
  return files;
}

function excludeLockFiles(files) {
    const newFiles = files;
    if (newFiles['package-lock.json']) {
        delete newFiles['package-lock.json'];
    }
    if (newFiles['yarn.lock']) {
        delete newFiles['yarn.lock'];
    }
    return files;
}