[RFC] Environment Variable Loading

[flybayer]

Problem

Blitz/Next use basically dotenv-flow to load env var files like .env, .env.test, .env.development.local, etc.

That behavior relies on setting NODE_ENV to the appropriate value before invoking a CLI command.

Problems:

1. Nextjs internals don't allow changing NODE_ENV. The build command must use NODE_ENV=production and dev must use NODE_ENV=development.
2. There's a new Nextjs bug that breaks previous usage of NODE_ENV=test blitz build
3. Now it's impossible to use NODE_ENV inside your app code to conditionally do things based on different environments.

Proposed Solution

Use APP_ENV to determine app environment instead of NODE_ENV. NODE_ENV will only be used for blitz dev vs blitz build.

The value of APP_ENV will determine which .env.[ENV].* files will be loaded.

1. Defaults:
   1. APP_ENV=development for blitz dev
   2. APP_ENV=production for blitz build and blitz start
   3. APP_ENV=test for Jest tests
2. Ways to manually specify APP_ENV:
   1. Set it before invoking the CLI like APP_ENV=test blitz start
   2. Set it with a new -e flag like blitz start -e test

With this solution, you can set APP_ENV to any string. Example: APP_ENV=staging which would load .env.staging

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Any and all feedback is welcome!

[lksnmnn]

Would that solution help us to make the ENV loading work better together with prisma? In our deployment, we currently overwrite .env to make it work.

[flybayer]

The existing solution for Prisma is to always use blitz prisma COMMAND instead of prisma COMMAND. blitz prisma will load all the appropriate .env files

[lksnmnn]

Oh, I wasn't reading up on that. Thanks! I'll give it a try.

[flybayer]

I've also posted this upstream in Next.js repo: vercel/next.js#25764