Support optional use of Yarn for packaging (instead of NPM)

[RishitKedia]

Hey! 👋

As discussed here with @HyperBrain, it'd be great if we could optionally use Yarn for packaging files, instead of NPM. 🙂

In particular, since serverless-webpack completely relies on NPM and uses it for packaging files, I'm having issues using serverless-webpack with Yarn Workspaces.

Currently, the bundled file is very huge (4 MB when used with Yarn Workspaces) compared to the same project when not used with Yarn Workspaces (25 kB). serverless-webpack bundles all the dependencies in one file even when using webpack-node-externals and webpackIncludeModules.

Thanks! 😃

[Gerst20051]

What's the status on this? Why doesn't this work while using yarn? @HyperBrain

[HyperBrain]

Because the plugin internally uses npm - and these are orthogonal in some regions (esp. workspaces and links - and finally the lock files).

Regarding the timeline: I'll try my best to phase this in asap.

In general, it would work like this:
You will have a new configuration variable custom: webpack: packager which can be npm (default) | yarn. Depending on this setting all calls currently done by using npm would be done by calling yarn with the similar commands`.

But first, from the architecture of the project, the packager itself (npm) should be abstracted into separate classes, so that yarn just can be added as additional packager. This approach will keep the way open for other packagers.

[Gerst20051]

Thanks! Would webpack-node-externals also need to be updated to support yarn or is this the only package that needs to be updated?

[HyperBrain]

No, only serverless-webpack. As far as I know node-externals reports external modules independently from the actually used packager.

[o-alexandrov]

@HyperBrain Thank you very much for the package.
Please consider also adding support for --flat:
$ yarn install --flat
Or, in other words, support for resolutions in package.json.

[HyperBrain]

@OlzhasAlexandrov Thanks for the hint :) I will consider it. As soon as I have something available in a PR, I'll write here, so that people can start testing and verifying.

[HyperBrain]

Update: Seems the first version of the Yarn packager works:

Serverless: Package lock found - Using locked versions
Serverless: Packing external modules: source-map-support@^0.5.3, flow-runtime@^0.16.0, bluebird@^3.5.1, lodash@^4.17.5, ...

This output is Yarn, not npm!

Serverless: Using configuration:
{
  "webpackConfig": "./webpack.config.js",
  "includeModules": true,
  "packager": "yarn",
  "packagerOptions": {},
  "packExternalModulesMaxBuffer": 204800
}

I will try to prepare a PR tomorrow, so that we have something that we can base further ideas (especially options and their defaults) onto. Stay tuned.