I am using Docker Compose to run a Rails application that has a component to read from the .env file as well (Dotenv: https://github.com/bkeepers/dotenv).

After trying to figure out why my environment variables were getting all messed up whenever I ran the app using Compose, I found out about Compose's ability to automatically read from .env, and realized it was affecting Dotenv's workflow, which ignores variables set by system.

Example:

• .env: VAR=0 (default value)
• .env.development: VAR=1

Expected behavior: VAR == 1

Upon launching the app in development, Dotenv will read from .env.development first and set VAR to 1 (because a system variable is not expected to be set). When it falls back to .env, VAR is already set so it won't be touched. This is how Dotenv's workflow works.

Received behavior: VAR == 0

Compose will have read from .env and set VAR to 0 in the system/container before launching the app. So when Dotenv reads .env.development, it will skip VAR because value will already be set by system.

I could set the development value directly in .env, but then, the same thing would happen in .env.test or any other local environment.

I don't generally use .env for Compose, so I'd like an option to disable this specific magic. Or just remove it, since I can already achieve the exact same thing using env_file, if I need it.

Thanks.