Typed Node ENV

🧨    💥    💪    Strictly typed access and type-casting for ENV variables    ✅    👨‍💻    😎

 

Notice: If you have any propositions feel free to make an issue or create a pull request.

📦 Installation

yarn add @z-brain/typed-node-env
or
npm i -s @z-brain/typed-node-env

🏃 Get started

Create a config class with decorated properties config.ts

import { EnvString, EnvInteger, EnvBoolean, Environment } from '@z-brain/typed-node-env';

@Environment()
export class EnvConfig {
  @EnvString()
  public readonly host!: string;

  @EnvInteger()
  public readonly port!: number;

  @EnvBoolean()
  public readonly production!: boolean;
}

const config = new EnvConfig();

console.log(
  config.host === 'test.net',
  config.port === 3000,
  config.production === false,
);

Due to the used decorators, the values for all properties can now be set via environment variables:

HOST=test.net PORT=3000 PRODUCTION=false ts-node config.ts

🎉 Benefits

• Type safety for your configuration:
  • No need to maintain a separate TypeScript interface
  • Types can be infered from the property's default value
  • Enforce correct types for values passed by environment variables and notifies about errors
  • Type-casting. For example fields with boolean type are correctly recognized from the well-known stringified values: 'true'/'false'/'1'/'0'
  • Automatically handles any kind of array types
• Take advantage of having a configuration class:
  • Calculate config values based on other config values (e.g. url from host and port)
  • Getter functions (e.g. get debugPort() { return this.port + 1000; })
  • Inherit from other configuration classes
• Enforce configuration values to be read-only at compile time (readonly modifier) and at runtime (enforceReadonly option)
• Load environment variables from a local file (using dotenv)

⚠️ Human-readable error messages

• A required ENV variable is absent:
  NoEnvVarError: Variable "BASE_URL" is required for AppConfig.baseUrl
• ENV variable value can't be casted to the specified type:

  TypeCastingError: AppConfig.debug: Boolean-like value expected, something else is gotten.
      Raw Value (string): "000"
      Env Var Name: "DEBUG"
      Is Array: false
  

• Int expected, a float has been gotten:

  AppConfig.logLevel: An Integer number expected, a Float is gotten.
      Raw Value (string): "11.1"
      Env Var Name: "LOG_LEVEL"
      Is Array: false
  

• Int array expected, one item of array is a string:

  TypeCastingError: Config.adminUserIDs: An Integer number expected, NaN is gotten.
      Raw Value (string): "11,22,abc,33"
      Env Var Name: "ADMIN_USER_IDS"
      Is Array: true
  

📚 Documentation

All decorators

• Type Casting property decorators
  • @EnvInteger()
  • @EnvFloat()
  • @EnvString()
  • @EnvBoolean()
  • @EnvEnum()
• Other
  • @EnvNested() To create nested configuration objects
  • @Environment() Wraps class and makes .loadEnvConfig() call during instantiating

Class property name & ENV variable name

Usually we write class properties in camelCase notation and environment variable names in SCREAMING_SNAKE_CASE notation. How can we relate them?

1. In a simple case typed-node-env package does internal transformation of class property name from came-case to ENV variable name in screaming-snake-case.
2. You can specify custom ENV name for a field.

     @EnvInteger('APP_PORT')
     public port!: number;
   

3. It is possible to specify multiple ENV names for the same property.
   In this case typed-node-env tries to find a first existing ENV variable in the order in which the names listed. @EnvInteger(['PORT', 'APP_PORT', 'HTTP_PORT']) public port!: number;
4. In case of nested object configured using @EnvNested() decorator
   1. By default, names of the property that contains a nested object is concatenated to each property name of the nested object.

      class DbConfig {
        @EnvString()
        public host!: string; // <--- DB_HOST
      
        @EnvInteger('PWD')
        public password!: string; // <--- DB_PWD (custom name is prefixed too)
      }
      
      class Config {
        @EnvNested()
        public db!: DbConfig;
      }

   2. Also, you can customize prefix name @EnvNested('MY_PREFIX')
5. It even possible to use the same config class for different fields to make complex nested object.

   class DbInsConfig {
     @EnvString()
     public host!: string;
     @EnvString()
     public login!: string;
     @EnvString()
     public password!: string;
   }
   class DbConfig {
     @EnvNested()
     master!: DbInsConfig;
     @EnvNested()
     slave!: DbInsConfig;
   }
   @Environment()
   class Config {
     @EnvNested()
     public db!: DbConfig;
   }
   const env = new Config();

   This config is looking for next variables:

   DB_MASTER_HOST      # ---> env.db.master.host
   DB_MASTER_LOGIN     # ---> env.db.master.login
   DB_MASTER_PASSWORD  # ---> env.db.master.password
   DB_SLAVE_HOST       # ---> env.db.slave.host
   DB_SLAVE_LOGIN      # ---> env.db.slave.login
   DB_SLAVE_PASSWORD   # ---> env.db.slave.password
   

Instantiating

1. The classic way is using new keyword.
   To use this way the config class should be decorated with @Environment() decorator.
   Notice: Internally during the instantiating of the class Environment decorator uses loadEnvConfig function under the hood.

   @Environment
   class EnvConfig {
     // ...
   }
   const env = new EnvConfig();

2. Manual loadEnvConfig() function call.
   It can be helpful if by some reasons you don't have to instantiate the config manually using new keyword. loadEnvConfig function works with both class constructors and with instances.

   // No @Environment() decorator here
   class EnvConfig {
     // ...
   }
   // env1 is a filled instance of EnvConfig
   const env1 = loadEnvConfig(EnvConfig);
   
   const env2Empty = new EnvConfig(); // totally empty object without any fields
   const env2 = loadEnvConfig(env2Empty);
   expect(env2Empty).toBe(env2);
   
   expect(env2).toEqual(env1); // all fields are equal

.allowEmpty flag

1. The default behavior is throwing an error about absent ENV variable in case the value of the variable is an empty string or a string filled only with spaces.

2. If we are decorate fields with any of @Env*({ allowEmpty: true }) decorators such "empty" values will be consumed and passed to type casting function.
   Here is a table of values to which such values will be converted by different decorators:

   decorator	input value	result
   EnvBoolean	' ' or ''	false
   EnvFloat	' ' or ''	0
   EnvInteger	' ' or ''	0
   EnvString	' '	' '
   EnvString	''	''
   EnvEnum	''	throws error except cases when an empty string is a enum option value
   EnvEnum	' '	throws error except cases when ' ' string is a enum option value

Handling arrays

Typed Node Env automatically detects array type and splits input ENV variables data by commas (,).

enum ETest {
  One  = 'one',
  Two  = 'two',
  Three = 'three',
}
@Environment()
class EnvConfig {
  @EnvString()
  public hosts!: string[]        // [ 'my.com', 'your.net' ]

  @EnvInteger()
  public ports!: number[]        // [ 80, 8080 ]

  @EnvFloat()
  public percentages!: number[]  // [ 0.75, 2.3 ]

  @EnvBoolean()
  public mask!: boolean[]        // [ false, false, true, false ]

  @EnvEnum(ETest)
  public testEnum!: ETest[]      // [ 'One', 'Two' ]
}
const env = new EnvConfig();

ENV variables

HOSTS=my.com,your.net
PORTS=80,8080
PERCENTAGES=0.75,2.3
MASK=false,false,true,false
TEST_ENUM=One,Two

Mixed types

You can define any mixed types for your properties and use multiple @Env*() decorators for the same property.

Use case for TypeORM .logging field handling

/** This is a complex type from TypeORM */
type LoggerOptions = boolean | 'all' | ('query' | 'schema' | 'error' | 'warn' | 'info' | 'log' | 'migration')[];

const allowedValues: LoggerOptions = ['query', 'schema', 'error', 'warn', 'info', 'log', 'migration'];
class EnvConfig {
    @EnvBoolean()
    @EnvEnum({ enum: allowedValues, isArray: true })
    @EnvEnum({ enum: ['all'] })
    public logging!: LoggerOptions;
}

Various of the ENV variable value:

LOGGING=true             # in TS will be transformed to true
LOGGING=all              # in TS will be transformed to 'all'
LOGGING=error,warn,info  # in TS will be transformed to ['error', 'warn', 'info']

More examples

You can find a lot of examples in the typed-env-integration.spec.ts

Similar projects

• https://github.com/igabesz/config-decorators
• https://github.com/jbpionnier/env-decorator
• https://github.com/Hippocrate/env-decorator
• https://github.com/derbenoo/ts-configurable

🔧 Development notes

Quick Start

cd /code/z-brain
git clone git@github.com:z-brain/typed-node-env.git
cd typed-node-env
yarn install

How to use NodeJS version from the .nvmrc

1. Install NVM

2. Use .nvmrc file one of the next ways:

   • Execute nvm use in the project root directory
   • Install NVM Loader and your .nvmrc will be loaded automatically when you open the terminal.

How to make a build

npm run build

How to run lint

• Just show problems npm run lint
• Fix problems if it is possible npm run lint:fix

How to run tests

• All tests

  npm run test
npm run test:watch

• Specific tests

  npm run test -- src/my.spec.ts
npm run test:watch -- src/my.spec.ts

How to build and publish NPM package

NPM Token: 6cf9...7ab8

CI configuration details are here: .github/workflows/npmpublish.yml

npm run pre-push
&& npm version patch -m 'Update package version version to %s'
&& npm run gen-public-package.json
&& cp README.md dist/
&& npm publish dist --access public
&& git push --no-verify && git push --tags --no-verify

How to build a package for local installation

1. yarn run build:local
2. Then you can install a local package build from path file:.../typed-node-env/dist.

👨‍💻 Author

Anton Korniychuk