SSR production build: Can I use ES6 modules?

[stefandesu]

Hi,

I'm using Vite's SSR together with Express. For certain reasons, I'm using the ES6 module syntax (i.e. import/export) for the whole project, not just for the Vite part.¹ However, the SSR production build produced by vite build --ssr src/entry-server.js --outDir dist/server uses the CommonJS syntax (exports/require) and thus is incompatible with the rest of the project. Therefore, when I try to run the project in production, I get an error: ReferenceError: exports is not defined.

I tried different options for vite build, like --target esnext, but no matter what I choose, I never get the ESM import/export syntax. When I manually convert the resulting entry-server.js file to use import/export, the production build works fine.

Is there any way to tell vite build to use ESM import/export syntax?

Thanks a lot!

¹: The thing is that I need a local module in both Express and Vite, and since Vite doesn't support require, I thought I'd just switch the whole project to ES6 modules.

[yyx990803]

For now the SSR build is always cjs for compatibility. You can use createRequire to load it in ESM mode.

[stefandesu]

Thanks Evan! I also had to rename entry-server.js to entry-server.cjs, but now it works. 👍