Expand environment variables

[marcolanaro]

🚀 Feature Proposal

It would be great to add the ability to interpolate variables.

Motivation

Often boxes come with some env variables that you want to use to declare other environment variables.

Example

Given the machine comes with an env variable like the following:

K8S_NAMESPACE=my_k8s_namespace

When in .env file we define the following

SERVICE_URL=https://prefix.$K8S_NAMESPACE.my.domain.com

Then the variable should be valued like:

SERVICE_URL=https://prefix.my_k8s_namespace.my.domain.com

This could be done in the app code, but consider the scenario where for local development the service url needs to have the following value:

SERVICE_URL=https://some.staging.environment.my.domain.com

In this case the app code should check the type of environment and then declare different strategies. It would be useful to just declare composable variables in the .env file.

Help

I could open a PR if you agree with the implementation.
From my point of view env-schema should provide a boolean expand options defaulted to false. When expand=true, internally use dotenv-expand.

[mcollina]

+1, would you like to send a PR?

[marcolanaro]

Brilliant!
PR opened here #36.