Environment Variables

Revali reads configuration in two ways. Pick one by asking when the value is known:

Secrets and anything that differs between staging and production belong at runtime. That way one build can be promoted from one environment to the next unchanged.

Env: Runtime Values#

import 'package:revali_router/revali_router.dart';

@App()
final class MainApp extends AppConfig {
  MainApp() : super.fromEnv();

  @override
  Future<void> configureDependencies(DI di) async {
    final env = Env.current;

    di.registerLazySingleton<Database>(
      () => Database(
        host: env.string('DB_HOST', orElse: 'localhost'),
        port: env.integer('DB_PORT', orElse: 5432),
        password: env.require('DB_PASSWORD'), // fails at startup, by name
      ),
    );
  }
}

DB_PASSWORD=secret dart run revali dev

• An empty or blank value counts as unset. Orchestrators often inject "" for variables nobody configured.
• A malformed value throws instead of falling back. For example, PORT=eighty stops the server rather than silently using 8080.
• boolean accepts true/1/yes/on and false/0/no/off, in any case.
• In tests, pass a map instead of changing the real environment: Env({'PORT': '9000'}).

AppConfig.fromEnv#

AppConfig.fromEnv reads host and port from the environment, so the same build runs on any platform:

MainApp() : super.fromEnv();

• The host defaults to 0.0.0.0, not localhost. Inside a container, a server bound to localhost refuses every connection from outside the container.
• The port comes from PORT. Cloud Run, Heroku, Render and Fly set PORT, and so do revali up and revali compose.
• The constructor isn't const, so your app's constructor can't be const either.

Compile-Time Values#

dart run revali dev --dart-define=APP_NAME=orders
dart run revali build --dart-define-from-file=.env.production

APP_NAME=orders
MAX_CONNECTIONS=50

const appName = String.fromEnvironment('APP_NAME', defaultValue: 'app');
const maxConnections = int.fromEnvironment('MAX_CONNECTIONS', defaultValue: 100);

Both flags can be repeated. The values are compiled into the program, and with a build: section they are compiled into the executable. Don't use them for secrets, and keep .env files out of source control.