Dotenvy

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Dotenvy is an Elixir implementation of the original dotenv Reby gem, compatible with mix and releases. It is designed to help the development of applications following the principles of the 12-factor app and its recommendation to store configuration in the environment.

Installation

Add dotenvy to your list of dependencies in mix.exs:

def deps do
  [
    {:dotenvy, "~> 0.3.0"}
  ]
end

It has no dependencies.

Usage

Dotenvy is designed to help configure your application at runtime, and one of the most effective places to do that is inside config/runtime.exs (available since Elixir v1.11).

The Dotenvy.source/2 function can accept a single file or a list of files. When combined with Config.config_env/0 it is easy to load up environment-specifc config, e.g.

source([".env", ".env.#{config_env()}", ".env.#{config_env()}.local"])

By default, the listed files do not need to exist -- the function only needs to know where to look. This makes it easy to commit default values while still leaving the door open to developers to override values via their own configuration files.

Unlike other packages, Dotenvy has no opinions about the names or locations of your dotenv config files, you just need to pass their paths to Dotenvy.source/2 or Dotenvy.source!/2.

For a simple example, we can load a single file:

# config/runtime.exs
import Config
import Dotenvy

source!(".env")

config :myapp, MyApp.Repo,
    database: env!("DATABASE", :string!),
    username: env!("USERNAME", :string),
    password: env!("PASSWORD", :string),
    hostname: env!("HOSTNAME", :string!),
    pool_size: env!("POOL_SIZE", :integer),
    adapter: env!("ADAPTER", :module, Ecto.Adapters.Postgres),
    pool: env!("POOL", :module?)

And then define your variables in the file(s) to be sourced. Dotenvy has no opinions about what you name your files; .env is merely a convention.

# .env
DATABASE=myapp_dev
USERNAME=myuser
PASSWORD=mypassword
HOSTNAME=localhost
POOL_SIZE=10
POOL=

When you set up your application configuration in this way, you are creating a contract with the environment (errors will be raised if certain system variables are not set because Dotenvy.env!/2 relies on System.fetch_env!/1), and this is an approach that works equally well for your day-to-day development and testing, as well as for mix releases.

Read the configuration strategies for more detailed examples of how to configure your app.

Refer to the "dotenv" (.env) file format for more examples and features of the supported syntax.

See the Dotenvy module documentation on its functions.

Note for Mix Tasks

If you have authored your own Mix tasks, you must ensure that they load the application configuration in a way that is compatible with the runtime config. A good way to do this is to include Mix.Task.run("app.config") inside the run/1 implementation, e.g.

def run(_args) do
  Mix.Task.run("app.config")
  # ...
end

If you are dealing with third-party mix tasks that fail to properly load configuration, you may need to manually call mix app.config before running them, e.g.

mix do app.config other.task

Image Attribution: "dot" by Stepan Voevodin from the Noun Project