`langium` package cannot be tree-shaken well

[jindong-zhannng]

Reproduction: https://github.com/jindong-zhannng/langium-bundle-test
Bundler: vite

There is only one import in main.ts (to simulate the case of generated/ast.ts):

import { AbstractAstReflection } from 'langium'

And class AbstractAstReflection also has zero dependency.

Expect: Bundle should only include AbstractAstReflection relevant code.
Actual:

(run npx vite-bundle-visualizer --open -o ./stats.html to generate report)

Obviously it includes lots of dead code like parser, validator and their dependencies. It brings the bundle size up to 174.67 kB (minified).

Idea

I tried to add "sideEffects": false to package.json. It significantly reduces the size to 1.27 kB and has a perfect report:

I'm not sure if it's suitable for langium and I also don't have a very good understanding of this setting. Just put it here for your reference.

[msujew]

Hey @jindong-zhannng,

thanks for the investigation. Since we actually don't feature any side effects, I've filed #1643. It will be released as part of 3.2 (hopefully next week).