env_flutter

Load configuration at runtime from a .env file which can be used throughout the application.

The twelve-factor app stores config in environment variables (often shortened to env vars or env). Env vars are easy to change between deploys without changing any code... they are a language- and OS-agnostic standard.

About

This library is a fork of java-james/flutter_dotenv dart library, with slight changes to make it read stage specific .env files.

An environment is the set of variables known to a process (say, PATH, PORT, ...). It is desirable to mimic the production environment during development (testing, staging, ...) by reading these values from a file.

This library parses that file and merges its values with the built-in Platform.environment map.

Usage

Create a .env file in the root of your project with the example content:

FOO=foo
BAR=bar
FOOBAR=$FOO$BAR
ESCAPED_DOLLAR_SIGN='$1000'
# This is a comment

Note: If deploying to web server, ensure that the config file is uploaded and not ignored. (Whitelist the config file on the server, or name the config file without a leading .)

Add all .env files to your assets bundle in pubspec.yaml. Ensure that the path corresponds to the location of the .env file!

assets:
  - .env
  - .env.development
  - .env.production
  - .env.test
  - .env.local
  - .env.development.local
  - .env.production.local
  - .env.test.local

Remember to add all the .env files as an entries in your .gitignore if it isn't already unless you want it included in your version control.

*.env

Load the .env file in main.dart.

import 'package:env_flutter/env_flutter.dart';

// DotEnv dotenv = DotEnv() is automatically called during import.
// If you want to load multiple dotenv files or name your dotenv object differently, you can do the following and import the singleton into the relavant files:
// DotEnv another_dotenv = DotEnv()

Future main() async {
  // To load the .env file contents into dotenv.
  // NOTE: fileName defaults to .env and can be omitted in this case.
  // Ensure that the filename corresponds to the path in step 1 and 2.
  await dotenv.load();
  //... run the app
}

You can then access variables from .env throughout the application

import 'package:env_flutter/env_flutter.dart';
dotenv.env['VAR_NAME'];

Optionally you could map env after load to a config model to access a config with types.

What other .env files can be used?

.env: Default.
.env.local: Local overrides. This file is loaded for all environments except test.
.env.development, .env.test, .env.production: Environment-specific settings.
.env.development.local, .env.test.local, .env.production.local: Local overrides of environment-specific settings.

Files on the left have more priority than files on the right:

flutter run: .env.development.local, .env.local, .env.development, .env
npm build: .env.production.local, .env.local, .env.production, .env
flutter test: .env.test.local, .env.test, .env (note .env.local is missing)

Advanced usage

Refer to the test/dotenv_test.dart file for a better idea of the behavior of the .env parser.

Referencing

You can reference variables defined above other within .env:

  FOO=foo
  BAR=bar
  FOOBAR=$FOO$BAR

You can escape referencing by wrapping the value in single quotes:

ESCAPED_DOLLAR_SIGN='$1000'

Merging

You can merge a map into the environment on load:

  await DotEnv.load(mergeWith: { "FOO": "foo", "BAR": "bar"});

You can also reference these merged variables within .env:

  FOOBAR=$FOO$BAR

Using in tests

There is a testLoad method that can be used to load a static set of variables for testing.

// Loading from a static string.
dotenv.testLoad(fileInput: '''FOO=foo
BAR=bar
''');

// Loading from a file synchronously.
dotenv.testLoad(fileInput: File('test/.env').readAsStringSync());

Null safety

To avoid null-safety checks for variables that are known to exist, there is a get() method that will throw an exception if the variable is undefined. You can also specify a default fallback value for when the variable is undefined in the .env file.

Future<void> main() async {
  await dotenv.load();

  String foo = dotenv.get('VAR_NAME');

  // Or with fallback.
  String bar = dotenv.get('MISSING_VAR_NAME', fallback: 'sane-default');

  // This would return null.
  String? baz = dotenv.maybeGet('MISSING_VAR_NAME', fallback: null);
}

Usage with Platform Environment

The Platform.environment map can be merged into the env:

  // For example using Platform.environment that contains a CLIENT_ID entry
  await DotEnv.load(mergeWith: Platform.environment);
  print(env["CLIENT_ID"]);

Like other merged entries described above, .env entries can reference these merged Platform.Environment entries if required:

  CLIENT_URL=https://$CLIENT_ID.dev.domain.com

Discussion

Use the issue tracker for bug reports and feature requests.

Pull requests are welcome.

rajkovukovic/env_flutter