Feature: Allow SSR build to output ES

[rschristian]

Is your feature request related to a problem? Please describe.

I'd like to use the SSR output as part of a larger application which has "type": "module" set. However, SSR is hard-coded to only output CJS.

vite/packages/vite/src/node/build.ts

Line 380 in c323732

format: ssr ? 'cjs' : 'es',

Describe the solution you'd like

I'd like to be able to customize/change this, best solution would probably be via Vite detecting the module type.

Describe alternatives you've considered

Could add another flag, but I think that's a bit much and I'd hesitate to add yet another.

Additional context

I'll probably write up a PR for this myself, but wanted to get this out there first.

[rschristian]

Looking into this more, it seems Vite is built on assumptions that modern output = browser. Might be a bigger change than I imagined. <-- Actually got changed from something unrelated so that's no longer an issue

[awacode21]

This is exactly my problem. I was so long searching for what I am doing wrong, it drove me totally crazy!!!!! But yeah, when it's hard coded...... we really should have the option to output ES.

As this issue is 1 year old, and there is still nothing merged... do you know any work around??
the server.js expects entry-server.js to be ES module, but in fact it got outputted as CJS. How can i workaround it to not be completely stopped with my work until this gets closed.

[awacode21]

Workaround with build.rollupOptions.output.format is possible.