loadEnv strategy

[FrankFang]

There are two strategies to load env vars (I choose the latter strategy in #2702), I am not sure which is better.

1 load all .env.* file and override the env

eg. you have .env and .env.local

1. load .env, override process.env
2. load .env.local, override the overrided process.env

Pros

.env.* files are merged, so you don't have to copy the entire content of .env to .env.local

Cons

vars in ~/.bashrc or specified in command line would be override, you have to write vars into any .env.* file

2 load one .env.* file but never override existing vars

eg. you have .env and .env.local

1. search for .env.local, exit once found it
2. search for .env, exit once found it
3. no override for process.env

Pros

vars in ~/.bashrc or specified in command line have a higher priority than ones in .env.*

Cons

You have to copy the entire content of .env to other .env.* files.

If .env is updated, you have to copy it again. Otherwise you may run into an error.

---

Any idea?

[FrankFang]

I find CRA's strategy is better, .env.* is merged but no override for existing environment variables

// Load environment variables from .env* files. Suppress warnings using silent
// if this file is missing. dotenv will never modify any environment variables
// that have already been set.  Variable expansion is supported in .env files.
// https://github.com/motdotla/dotenv
// https://github.com/motdotla/dotenv-expand
dotenvFiles.forEach(dotenvFile => {
  if (fs.existsSync(dotenvFile)) {
    require('dotenv-expand')(
      require('dotenv').config({
        path: dotenvFile,
      })
    );
  }
});