Environment variables

[alatielle]

Hi folks! Thanks for doing an awesome job 💟

I stumbled upon a confusing behaviour yesterday which seems to be undocumented.
Imagine a scenario:

1. You have some secrets in gitlab that are exported as environment variables in CI
2. Your build script takes them and puts them into the .env.production.local file
3. Then, when all necessary variables are in place, astro build is called.

What happened when built locally
Variable values were interpolated into the built code like this:
const API_TOKEN = "secret"

What happened in CI
const API_TOKEN = process.env.API_TOKEN

After excessive googling and consulting the docs of both Astro and Vite we could not find anything that would explain this behaviour. Eventually we figured it out: when the variable is set but is also present in some .env file, it won't be set again. Instead, it will be expected to be present and be provided in runtime. Everything worked as expected after unsetting those variables.

I think this behaviour should be documented! What do you think?