svelte-kit preview doesn't pick up env vars declared in .env

[Rich-Harris]

Describe the problem

During development, Vite loads .env files according to this logic. svelte-kit preview doesn't read .env files; as such, env vars are missing.

Describe the proposed solution

Load .env files with the same logic Vite uses (this is handwavy — Vite allows arbitrary 'modes', so it's unclear which file(s) we'd load in preview beyond .env and .env.local. .env.prod and .env.prod.local?)

Alternatives considered

No response

Importance

would make my life easier

Additional Information

No response

[Conduitry]

Hmm I have mixed feelings about whether this would be the desired behavior. Production builds don't automatically look at .env (I admit I haven't specifically checked, but I hope they do not!) so why should previews?

preview loading .env might be convenient, but it sounds unwise to me. As in production, you should be responsible for making sure the environment variables in question are actually present in your environment.

[matmoxam]

I think this is in relation to using tools like dotenv and env-cmd. The intended purpose is to load env variables at runtime. Is there a better way to load env variables at runtime?

[Rich-Harris]

closing in favour of #4296