Components styled with emotion do not get theme from material theme provider about vitest HOT 3 OPEN

I tried to decipher what's happening but unfortunately I couldn't figure out yet where this goes wrong. https://github.com/hi-ogawa/reproductions/tree/main/vitest-5664-mui-emotion-provider

It seems like Vite SSR is fine, so Vitest / Vite-node might be making bad resolution. It could be a bug, so we can leave this issue open.

from vitest.

As indicated by the warning:

stderr | node_modules/@ emotion/react/dist/emotion-react.esm.js:472:15
You are loading @emotion/react when it is already loaded. Running multiple instances may cause problems. This can happen if multiple versions are used, or if multiple builds of the same version are used.

this is a dual package issue of @emotion/react. The one imported through @mui/material (via NodeJS) and the other from your source code (via Vite/Vitest) are seeing different context singleton.

It looks like NodeJS is loading @emotion/react/dist/emotion-react.cjs.mjs, so you can force Vitest's resolution via alias:
https://stackblitz.com/edit/vitest-dev-vitest-wpfmsa?file=vitest.config.ts

  test: {
    alias: {
      '@emotion/react': path.resolve(
        'node_modules/@emotion/react/dist/emotion-react.cjs.mjs'
      ),
    },
  },

Looking at https://publint.dev/@emotion/[email protected], the package exports is quite complicated, but seems legitimate, so it might be possible that Vite / Vitest's default resolution is doing something wrong.

from vitest.

Well as workaround this works but I think it is not good that vite and vitest behave in a different way.
Isn't there a way to force the loading of the correct module on vitest side?

from vitest.