• Table of Contents
• Overview
• Install
• Usage
  • Obfuscation/Encryption
  • Optional Environment Variables
  • Environment Variable Naming Conventions
  • Using System Environment Variables
  • Setting file from CLI
• Known Issues
• License

Using a .env file such as:

KEY=VALUE

or system environment variables such as:

export VAR=test

and a dart class:

import 'package:envied/envied.dart';

part 'env.g.dart';

@envied
abstract class Env {
    @EnviedField(varName: 'KEY')
    static const String key = _Env.key;
}

Envied will generate the part file which contains the values from your .env file using build_runner

You can then use the Env class to access your environment variable:

print(Env.key); // "VALUE"

Add both envied and envied_generator as dependencies,

If you are using creating a Flutter project:

$ flutter pub add envied
$ flutter pub add --dev envied_generator
$ flutter pub add --dev build_runner

If you are using creating a Dart project:

$ dart pub add envied
$ dart pub add --dev envied_generator
$ dart pub add --dev build_runner

This installs three packages:

• build_runner, the tool to run code-generators
• envied_generator, the code generator
• envied, a package containing the annotations.

Add a .env file at the root of the project. The name of this file can be specified in your Envied class if you call it something else such as .env.dev.

KEY1=VALUE1
KEY2=VALUE2

Create a class to ingest the environment variables (lib/env/env.dart). Add the annotations for Envied on the class and EnviedField for any environment variables you want to be pulled from your .env file.

IMPORTANT! Add both .env and env.g.dart files to your .gitignore file, otherwise, you might expose your environment variables.

// lib/env/env.dart
import 'package:envied/envied.dart';

part 'env.g.dart';

@Envied(path: '.env.dev')
abstract class Env {
    @EnviedField(varName: 'KEY1')
    static const String key1 = _Env.key1;
    @EnviedField()
    static const String KEY2 = _Env.KEY2;
    @EnviedField(defaultValue: 'test_')
    static const String key3 = _Env.key3;
}

Then run the generator:

dart run build_runner build

You can then use the Env class to access your environment variables:

print(Env.key1); // "VALUE1"
print(Env.KEY2); // "VALUE2"

Add the obfuscate flag to EnviedField

@EnviedField(obfuscate: true)

Please keep in mind that this only increases the amount of effort to retrieve the obfuscated/encrypted values. If someone tries hard enough, he will eventually find the values. For more information, see frencojobs/envify#28 and #4!

Enable allowOptionalFields to allow nullable types. When a default value is not provided and the type is nullable, the generator will assign the value to null instead of throwing an exception.

By default, optional fields are not enabled because it could be confusing while debugging. If a field is nullable and a default value is not provided, it will not throw an exception if it is missing an environment variable.

For example, this could be useful if you are using an analytics service for an open-source app, but you don't want to require users or contributors to provide an API key if they build the app themselves.

@Envied(allowOptionalFields: true)
abstract class Env {
    @EnviedField()
    static const String? optionalServiceApiKey = _Env.optionalServiceApiKey;
}

Optional fields can also be enabled on a per-field basis by setting

@EnviedField(optional: true)

The envied package provides a convenient way to handle environment variables in Dart applications. With the addition of the useConstantCase flag in the @EnvField and @Envied annotation, developers can now easily adhere to the Dart convention for constant names. The useConstantCase flag allows the automatic transformation of field names from camelCase to CONSTANT_CASE when the @EnvField annotation is not explicitly assigned a varName.

By default, this is set to false, which means that the field name will retain its original format unless varName is specified. When set to true, the field name will be automatically transformed into CONSTANT_CASE, which is a commonly used case type for environment variable names.

@Envied(path: '.env', useConstantCase: true)
final class Env {

    @EnviedField()
    static const String apiKey = _Env.apiKey; // Transformed to 'API_KEY'


    @EnviedField(varName: 'apiKey')
    static const String apiKey = _Env.apiKey; // Searches for a variable named 'apiKey' inside the .env file and assigns it to apiKey

}

This option can also be enabled on a per-field basis by setting

@EnviedField(useConstantCase: true)
static const String apiKey; // Transformed to 'API_KEY'

@EnviedField()
static const String apiKey; // Retains its original value, which is `apiKey`

@EnviedField(varName: 'DEBUG_API_KEY')
static const String apiKey; // Searches for a variable named 'DEBUG_API_KEY' inside the .env file and assigns it to apiKey

These example illustrates how the field name apiKey is automatically transformed to API_KEY, adhering to the CONSTANT_CASE convention commonly used as the variable name inside the .env file. This feature contributes to improved code consistency and readability, while also aligning with Effective Dart naming conventions.

You can override the default .env file path by creating a build.yaml file in the root of your project.

targets:
  $default:
    builders:
      envied_generator|envied:
        options:
          path: .env.custom
          override: true 

Note that both path and override must be set for the override to work.

Using the environment option in either an Envied or EnviedField instructs the generator to use the value from the .env file as the key for a system environment variable read from Platform.environment.

For example, let's use the Envied class and the following .env files:

@Envied(environment: true)
final class Env {
  @EnviedField(varName: 'API_KEY')
  static const  String apiKey = _Env.apiKey;
}

... or ...

@Envied()
final class Env {
  @EnviedField(environment: true, varName: 'API_KEY')
  static const  String apiKey = _Env.apiKey;
}

latest.env

API_KEY=LATEST_API_KEY

stage.env

API_KEY=STAGE_API_KEY

Depending on which .env file you use to generate can result in the API_KEY being read from either Platform.environment['LATEST_API_KEY'] or Platform.environment['STAGE_API_KEY']. This can allow for the .env files to be safely checked in to the source control, the specific values to be set at build time, and keep the secrets safely stored in the host environment.

For instructions on switching the .env file at build time, see Setting file from CLI.

To change which .env file is used by default using the CLI, pass it in via the --define flag as follows:

dart run build_runner build --define=envied_generator:envied=path=my_other.env

This allows you to have multiple .env files, one per backend for instance, and then switch which one gets included in the build easily from CI/CD scripts such as github workflows.

When modifying the .env file, the generator might not pick up the change due to dart-lang/build#967. If that happens simply clean the build cache and run the generator again.

dart run build_runner clean
dart run build_runner build --delete-conflicting-outputs

For more information please see petercinibulk/envied#6 and/or the original issue dart-lang/build#967.

MIT © Peter Cinibulk