当前 SvelteKit 项目中的 process.env.NODE_ENV 突然未定义

Question

Inside svelte.config.js I was using this

const dev = process.env.NODE_ENV === 'development';

to conditionally set a base path which was working fine in projects with @sveltejs/kit@1.0.0-next.350 and *.357

After installing now the most recent SvelteKit version @sveltejs/kit@1.0.0-next.386 it only results to undefined

Differences I notice is that the new project lists "vite": "^3.0.0" as devDependency and the script changed from "dev": "svelte-kit dev", to "dev": "vite dev"

Update: It's also the case for a project with @sveltejs/kit@1.0.0-next.366 , vite@2.9.14 , "dev": "vite dev" - so the switch was before vite 3.0

Going through the vite docs I find import.meta.env , but that's also undefined inside svelte.config.js

Switching from Node v16 to 17 didn't make a difference as well

What changed and how can I now distinguish between dev and build mode?

Answer 1

The behavior you describe was introduced in 100-next384

[breaking] remove mode, prod and server from $app/env (#5602)

and here is the relevant discussion

respect --mode, and remove server, prod and mode from $app/env

I think you should use Vite capabilities to configure dev VS production/build modes.

Update

Considering better your case, a way to solve the issue is to set a value for the NODE_DEV environment variable, like (Linux/Mac):

export NODE_ENV=development && npm run dev

There are other ways to do this but at least for development it should do the trick.

Answer 2

This might help someone in the future. I encountered this error when I created an express server in a react application. I created the server directory in the root folder of the react application and I was running both react app and express server at the same time.