[Bug]: Investigate code getting pre-bundled multiple times

[shilman]

Describe the bug

Inside the new preview-api package things appear to be included too many times. For example:

shilman@MBP14 lit-vite-default-js % grep getSelectionSpecifierFromPath node_modules/@storybook/preview-api/dist/*
node_modules/@storybook/preview-api/dist/chunk-S6GMWV4D.mjs:var getSelectionSpecifierFromPath = () => {
node_modules/@storybook/preview-api/dist/chunk-S6GMWV4D.mjs:    this.selectionSpecifier = getSelectionSpecifierFromPath();
node_modules/@storybook/preview-api/dist/core-client.js:var getSelectionSpecifierFromPath = () => {
node_modules/@storybook/preview-api/dist/core-client.js:    this.selectionSpecifier = getSelectionSpecifierFromPath();
node_modules/@storybook/preview-api/dist/index.js:var getSelectionSpecifierFromPath = () => {
node_modules/@storybook/preview-api/dist/index.js:    this.selectionSpecifier = getSelectionSpecifierFromPath();
node_modules/@storybook/preview-api/dist/preview-web.js:var getSelectionSpecifierFromPath = () => {
node_modules/@storybook/preview-api/dist/preview-web.js:    this.selectionSpecifier = getSelectionSpecifierFromPath();

Note that this is also bundled in the preview package as well, further contributing to the install size.

This may contribute to a ballooning install size in our benchmarks:

To Reproduce

No response

System

No response

Additional context

No response

[ndelangen]

These are all the commonJS files, which do indeed not tree-shake, and for backwards compatibility have all the old code still present/bundled.

What are we measuring here?

[ndelangen]

I can't say with full confidence, but I think these commonjs files would only ever be used by storyshots, I think.

[ndelangen]

I verified that the MJS files are in the prebundle.

[ndelangen]

I have noticed that the deprecation warnings for the removed packages don't actually make it into the ESM dist (they do appear in the CJS dist)

[ndelangen]

I verified, that in the webpack-builder the externalisation of the packages we want work correctly, and they are all ESM.

[ndelangen]

I found that vite-builder was using :

import externalGlobals from 'rollup-plugin-external-globals';

But this resulted in the code existing multiple times.
Switching to

import { viteExternalsPlugin } from 'vite-plugin-externals';

made it work!

[ndelangen]

will open a PR.

[shilman]

w00t!! I just released https://github.com/storybookjs/storybook/releases/tag/v7.0.0-beta.26 containing PR #20594 that references this issue. Upgrade today to the @next NPM tag to try it out!

npx sb@next upgrade --prerelease

Closing this issue. Please re-open if you think there's still more to do.