Ambient.Config (Ambient v0.1.0)

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An app-config accessor with a per-process override layer for test isolation.

use it once to bind it to your OTP application:

defmodule MyApp.Config do
  use Ambient.Config, otp_app: :my_app
end

This generates the domain API – get/2, put/2, revert/1, reset/0 – where get/2 reads a per-process override first (via Ambient.ProcessOverride), then falls back to Application.get_env(:my_app, key, default).

Underneath, Ambient.Value supplies the generic layer those wrap (put_override/2, delete_override/1, delete_all/0) plus overridden?/1, allow/2, set_shared/1 and set_private/0. You can use Ambient.Value directly to build overridable values of your own.

Why not Application.put_env/3 in tests?

Application.put_env/3 is global – concurrent async: true tests clobber each other. put/2 is process-local, inherited by spawned children ($callers + allow/2), and auto-cleaned on exit. Safe under async: true.

Usage

# production / app code
MyApp.Config.get(:feature_x_enabled, false)

# tests
MyApp.Config.put(:feature_x_enabled, true)
MyApp.Config.revert(:feature_x_enabled)
MyApp.Config.reset()

# for a GenServer that reads config in its own process:
MyApp.Config.allow(genserver_pid)

Remember to start the override server for the generated table in test/test_helper.exs:

Ambient.start_servers([MyApp.Config])