SnowingFox / env-typed-config

Intuitive, type-safe configuration library for Node.js

env-typed-config

Never write strings to read config again.

Features

• Load your configuration with environment variables, json/yaml/toml configuration files.
• Validate your configuration with class-validator and class-transformer.
• Provide easy to use options by default, meanwhile everything is customizable.

Installation

$ npm i env-typed-config

env-typed-config will install the dependencies for all loaders by default. If you care about dependency size and bootstrap time, please checkout the guide to skip optional dependencies.

Inspiration

Thanks to the nest-typed-config library

There are various popular configuration library in Node.js like dotenv

const port: number = process.env.SERVER_PORT;
const host: string = process.env.SERVER_HOST;

Writing strings to read config is error-prone and hard to maintain. env-typed-config provides a better way to read config with type safety and validation.

#.env.toml
[server]
host = "localhost"
port = 3000

// config.ts
export class AppConfig {
  @IsString()
  public readonly host!: string;

  @IsNumber()
  public readonly port!: number;
}

// typed.config.ts
import { AppConfig } from './config';

export const config = await defineConfig({
  schema: AppConfig,
  load: fileLoader(),
});

console.log(config.host); // "localhost"

Quick Start

Let's define the configuration model first. It can be nested at arbitrary depth.

// config.ts
import { Allow, ValidateNested } from 'class-validator';

// validator is omitted for simplicity
export class TableConfig {
  @Allow()
  public readonly name!: string;
}

export class DatabaseConfig {
  @Type(() => TableConfig)
  @ValidateNested()
  public readonly table!: TableConfig;
}

export class RootConfig {
  @Type(() => DatabaseConfig)
  @ValidateNested()
  public readonly database!: DatabaseConfig;
}

Then, add a configuration file such as .env.yaml under project root directory:

database:
  table:
    name: example

Using loaders

Using dotenv loader

The dotenvLoader function allows you to load configuration with dotenv, which is similar to the official configuration module. You can use this loader to load configuration from .env files or environment variables.

Example

const config = defineConfig({
  schema: RootConfig,
  load: dotenvLoader({
    /* options */
  }),
});

Passing options

The dotenvLoader function optionally expects a DotenvLoaderOptions object as a first parameter:

export interface DotenvLoaderOptions {
  /**
   * If set, use the separator to parse environment variables to objects.
   *
   * @example
   *
   * ```bash
   * app__port=8080
   * db__host=127.0.0.1
   * db__port=3000
   * ```
   *
   * if `separator` is set to `__`, environment variables above will be parsed as:
   *
   * ```json
   * {
   *     "app": {
   *         "port": 8080
   *     },
   *     "db": {
   *         "host": "127.0.0.1",
   *         "port": 3000
   *     }
   * }
   * ```
   */
  separator?: string;

  /**
   * If "true", environment files (`.env`) will be ignored.
   */
  ignoreEnvFile?: boolean;

  /**
   * If "true", predefined environment variables will not be validated.
   */
  ignoreEnvVars?: boolean;

  /**
   * Path to the environment file(s) to be loaded.
   */
  envFilePath?: string | string[];

  /**
   * A boolean value indicating the use of expanded variables.
   * If .env contains expanded variables, they'll only be parsed if
   * this property is set to true.
   *
   * Internally, dotenv-expand is used to expand variables.
   */
  expandVariables?: boolean;
}

Using file loader

The fileLoader function allows you to load configuration with cosmiconfig. You can use this loader to load configuration from files with various extensions, such as .json, .yaml, .toml or .js.

By default, fileLoader searches for .env.{ext} (ext = json, yaml, toml, js) configuration file starting at process.cwd(), and continues to search up the directory tree until it finds some acceptable configuration (or hits the home directory). Moreover, configuration of current environment takes precedence over general configuration (.env.development.toml is loaded instead of .env.toml when NODE_ENV=development)

Example

const config = defineConfig({
  schema: RootConfig,
  load: fileLoader({
    /* options */
  }),
});

Passing options

The fileLoader function optionally expects a FileLoaderOptions object as a first parameter:

import { OptionsSync } from 'cosmiconfig';

export interface FileLoaderOptions extends Partial<OptionsSync> {
  /**
   * basename of config file, defaults to `.env`.
   *
   * In other words, `.env.yaml`, `.env.yml`, `.env.json`, `.env.toml`, `.env.js`
   * will be searched by default.
   */
  basename?: string;
  /**
   * Use given file directly, instead of recursively searching in directory tree.
   */
  absolutePath?: string;
  /**
   * The directory to search from, defaults to `process.cwd()`. See: https://github.com/davidtheclark/cosmiconfig#explorersearch
   */
  searchFrom?: string;
  /**
   * If "true", ignore environment variable substitution.
   * Default: true
   */
  ignoreEnvironmentVariableSubstitution?: boolean;
}

If you want to add support for other extensions, you can use loaders property provided by cosmiconfig:

Using multiple loaders

Loading configuration from file system is convenient for development, but when it comes to deployment, you may need to load configuration from environment variables, especially in a dockerized environment. This can be easily achieved by providing multiple loaders. For example:

const config = defineConfig({
  schema: RootConfig,
  // Loaders having larger index take precedence over smaller ones,
  // make sure dotenvLoader comes after fileLoader ensures that
  // environment variables always have the highest priority
  load: [
    fileLoader({
      /* options */
    }),
    dotenvLoader({
      /* options */
    }),
  ],
});

Using custom loader

If native loaders provided by env-typed-config can't meet your needs, you can implement a custom loader. This can be achieved by providing a function which returns the configuration object synchronously or asynchronously through the load option. For example:

const config = defineConfig({
  schema: RootConfig,
  load: async () => {
    return {
      host: '127.0.0.1',
      port: 3000,
    };
  },
});

Uses of environment variable substitutions

The ${PORT} substitution feature lets you use environment variable in some nice ways.

If you have config file with like the below one

database:
  host: 127.0.0.1
  port: ${PORT}

And you have set environment variable for port

PORT=9000

And set ignoreEnvironmentVariableSubstitution to false in the FileLoaderOptions

load: fileLoader({
  ignoreEnvironmentVariableSubstitution: false,
}),

then fileloader will resolve ${PORT} placeholder and replace with environment variable. And you will get new config like below one

database:
  host: 127.0.0.1
  port: 9000

Default values

Just define your default values in config schema, and you are ready to go:

// config.ts
export class Config {
  @IsString()
  public readonly host: string = '127.0.0.1';

  @IsNumber()
  public readonly port: number = 3000;
}

Transforming the raw configuration

Environment variables are always loaded as strings, but configuration schemas are not. In such case, you can transform the raw config with normalize function:

// config.ts
export class Config {
  @IsString()
  public readonly host: string;

  @IsNumber()
  public readonly port: number;
}

// typed.config.ts
const config = defineConfig({
  schema: RootConfig,
  load: dotenvLoader(),
  normalize(config) {
    config.port = parseInt(config.port, 10);
    return config;
  },
});

Custom getters

You can define custom getters on config schema to extract common logic:

export class Config {
  @IsString()
  public readonly host: string = '127.0.0.1';

  @IsNumber()
  public readonly port: number = 3000;

  @IsString()
  public get url(): string {
    return `http://${this.host}:${this.port}`;
  }
}

Custom validate function

If the default validate function doesn't suite your use case, you can provide it like in the example below:

const config = defineConfig({
  schema: RootConfig,
  validate: (rawConfig: any) => {
    const config = plainToClass(RootConfig, rawConfig);
    const schemaErrors = validateSync(config, {
      forbidUnknownValues: true,
      whitelist: true,
    });

    if (schemaErrors.length) {
      throw new Error(TypedConfigModule.getConfigErrorMessage(schemaErrors));
    }

    return config as RootConfig;
  },
});

License

MIT.

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License

MIT License © 2023 Snowingfox