yarnpkg/yarn · error · MessageError

lockfileExists

Error message

lockfileExists

What it means

`yarn import` is designed as a one-time migration from npm to yarn; `init()` at `import.js:372` refuses to run if a `yarn.lock` already exists in `config.cwd`. It throws `lockfileExists` ('Lockfile already exists, not importing.') to avoid overwriting an existing yarn lockfile.

Source

Thrown at src/cli/commands/import.js:372

      this.resolver.dependencyTree = new LogicalDependencyTree(packageJson, packageLock);
    } catch (e) {
      throw new MessageError(this.reporter.lang('importSourceFilesCorrupted'));
    }
  }
  async getExternalLockfileContents(): Promise<{packageJson: ?string, packageLock: ?string}> {
    try {
      const [packageJson, packageLock] = await Promise.all([
        fs.readFile(path.join(this.config.cwd, NODE_PACKAGE_JSON)),
        fs.readFile(path.join(this.config.cwd, NPM_LOCK_FILENAME)),
      ]);
      return {packageJson, packageLock};
    } catch (e) {
      return {packageJson: null, packageLock: null};
    }
  }
  async init(): Promise<Array<string>> {
    if (await fs.exists(path.join(this.config.cwd, LOCKFILE_FILENAME))) {
      throw new MessageError(this.reporter.lang('lockfileExists'));
    }
    const {packageJson, packageLock} = await this.getExternalLockfileContents();
    const importSource =
      packageJson && packageLock && semver.satisfies(nodeVersion, '>=5.0.0') ? 'package-lock.json' : 'node_modules';
    if (importSource === 'package-lock.json') {
      this.reporter.info(this.reporter.lang('importPackageLock'));
      this.createLogicalDependencyTree(packageJson, packageLock);
    }
    if (importSource === 'node_modules') {
      this.reporter.info(this.reporter.lang('importNodeModules'));
      await verifyTreeCheck(this.config, this.reporter, {}, []);
    }
    const {requests, patterns, manifest} = await this.fetchRequestFromCwd();
    if (manifest.name && this.resolver instanceof ImportPackageResolver) {
      this.resolver.rootName = manifest.name;
    }
    await this.resolver.init(requests, {isFlat: this.flags.flat, isFrozen: this.flags.frozenLockfile});
    const manifests: Array<Manifest> = await fetcher.fetch(this.resolver.getManifests(), this.config);

View on GitHub (pinned to c2dda503f3)

Solutions

1. If migration is intentional, delete the existing `yarn.lock` and rerun `yarn import`.
2. Otherwise treat this as an expected guard — your project already uses yarn; just run `yarn install`.
3. Verify you are in the correct project root before importing.

Example fix

// before
$ yarn import
→ Lockfile already exists, not importing.

// after (re-import)
$ rm yarn.lock && yarn import

import fs from 'fs';

function assertNoYarnLock(cwd: string): void {
  if (fs.existsSync(`${cwd}/yarn.lock`)) {
    throw new Error('yarn.lock already exists; remove it before `yarn import` or skip import');
  }
}

try {
  await yarnImport();
} catch (e) {
  if (/Lockfile already exists, not importing/.test(e.message)) {
    // expected guard — decide: delete yarn.lock to re-import, or just yarn install
  } else throw e;
}

When it happens

Trigger: `fs.exists(path.join(config.cwd, LOCKFILE_FILENAME))` (i.e. `yarn.lock` present) returns true at the top of `Import.init()`.

Common situations: Running `yarn import` after `yarn install` already created yarn.lock, a leftover yarn.lock from a previous attempt, or running import in the wrong directory.

Related errors

• workspacesAddRootCheck
• importResolveFailed
• importSourceFilesCorrupted
• frozenLockfileError
• noRequiredLockfile

AI-assisted analysis of yarnpkg/yarn@c2dda503f3 (2026-08-13). Data as JSON: /api/errors/2ade7e1440f6238e. Report an issue: GitHub.