Using Lerna with unpublished packages

Question

I'm trying to set up my monorepo with Lerna. The plan is to refactor an existing project by pulling chunks of code out which should be their own packages. I've run lerna init, and my current setup looks like this:

project/
  packages/
    new-refactored-package/
      package.json
    prior-existing-project/
      package.json
        { "dependencies" : { "new-refactored-package" : "latest" } }
  package.json
    {
      "devDependencies": {
        "lerna": "^2.0.0-rc.5"
      }
    }
  lerna.json
    {
      "lerna": "2.0.0-rc.5",
      "packages": [
        "packages/*"
      ],
      "version": "0.0.0"
    }

My understanding was that lerna bootstrap at this point is supposed to locate package1 in the project and symlink it to prior-existing-project's /node_modules/new-refactored-package/. From lerna's readme:

Bootstrap the packages in the current Lerna repo. Installs all of their dependencies and links any cross-dependencies.

When run, this command will:

• npm install all external dependencies of each package.
• Symlink together all Lerna packages that are dependencies of each other.
• npm prepublish all bootstrapped packages.

However, when I run it, lerna attempts instead to npm install new-refactored-package:

npm ERR! 404 Registry returned 404 for GET on https://registry.npmjs.org/new-refactored-package

Am I misunderstanding? Do I first have to publish the depended-upon packages to npm?

Answer 1

Requirements

For lerna to symlink a local package when running lerna bootstrap the local package must have a name and version that matches. Whenever lerna cannot match a dependency to a local package, it'll try to install it from the registry.

So ensure that the dependency package has a version that can be matched by the semver version in the dependant.

Example

{

  name: "@my-name/dependency",
  version: "1.2.0"
}

{
  name: "@my-name/dependant",
  dependencies: {
    "@my-name/dependency": "<VERSION>"
  }
}

@my-name/dependency will be symlinked when VERSION is 1.2.0, ^1.0.0, 1.X.X, or *. However when using ranges that does not match the local package, like 1.0.0 or ^0.0.0, it will try to resolve it in the npm registry and will show the error like 404 Not Found - GET https://registry.npmjs.org/@my-name%2fdependency - Not found.

latest

In the actual scenario that is explained in the question, the actual issue is that the version is specified as latest and while it's easy to think that latest is a generic term for the latest version available, it's actually a npm-dist-tag which is applied by default to all new releases.

If you look at packages like react (click versions), you can see that other than the latest, they also deploy releases with tags next, canary and unstable.

Your unpublished package does not have any tags, as they are applied on publication, and so latest will not match, meaning lerna will try to resolve it remotely, failing with 404.

This is noted as one of the gotchas in the Notes of the documentation for the bootstrap command.

• When a dependency version in a package is not satisfied by a package of the same name in the repo, it will be npm installed (or yarned) like normal.
• Dist-tags, like latest, do not satisfy semver ranges.
• Circular dependencies result in circular symlinks which may impact your editor/IDE.

Solution

If you want to match whatever version that is available, the recommended path would be to set the version to "*". This will match any version and will thus always use the local version, given that the local package has a specified version field.

{ 
  "dependencies": { 
    "new-refactored-package" : "*"
  }
}

alpha, rc or beta

Even * will not match versions that are marked as pre-release, so if you give your local package a version like 0.0.1-alpha.0, or 1.0.0-rc.3, it will also not be locally symlinked

private: true

While it does not affect lerna bootstrap, it's worth mentioning that packages that you do not want to be published should always have private: true;. This will ensure that lerna publish does not publish it.