Using vite-plugin-solid with vitest workspaces prevents solid-js from resolving correctly

Start with the linked StackBlitz reproduction and run npm run test-all, then compare it with npm run test-fe-only and npm run test-all-no-plugin. Inspect how vite-plugin-solid interacts with Vitest workspaces and the solid-js resolution shown in node_modules/solid-js/store/dist/dev.js. Done means the workspace test calling createStore no longer throws while the plugin remains enabled.

Description

Vitest has a workspaces feature, where vitest can be made aware of different sub-projects, and run the tests for each of these workspaces (based on their individual configuration) together.

However, when using Vitest workspaces and vite-plugin-solid, the solid-js resolution system fails to work properly, and functions like createStore() throw errors.

Reproduction

https://stackblitz.com/edit/solidjs-templates-4usktg?file=README.md&view=editor

The problem can be reproduced by running npm run test-all in the console. This runs a test that just calls createStore.

Running npm run test-fe-only runs vitest in the frontend/ package, which bypasses Vitest's workspaces system, everything works again.

Running npm run test-all-no-plugin runs vitest the same as in test-all, but with the vite-plugin-solid plugin disabled. Again, this works as expected.

Error/Investigation

The error returned is:

TypeError: Cannot read properties of undefined (reading 'registerGraph')
 ❯ Module.createStore node_modules/solid-js/store/dist/dev.js:213:9
 ❯ packages/frontend/src/test.spec.ts:6:36

This is because in dev-mode, the createStore tries to access the DEV object exported by solid-js. This DEV object is only available if solid-js is running in dev mode (in production, a different file is used which sets DEV to undefined).

However, for some reason, when Vite/NodeJS/Vitest/? tries to resolve the import solid-js from node_modules/solid-js/store/dist/dev.js, it instead imports the production version of solid-js, which obviously doesn't have the correct exported DEV object, and so an error is thrown.

I'm creating this issue here, because the error only occurs if vite-plugin-solid is installed, but I'm not entirely sure what this plugin is doing that makes things behave weirdly here. There isn't any JSX to process, so I would have through the plugin is essentially a no-op.

Thanks for any help!