@unifig/core

Unifig

Universal, typed and validated configuration manager.

Table of Contents

• Installation
• Setting up Templates
  • Subtemplates
• Using Configuration
  • Quick Start
  • Values Adapters
    • Types conversion
    • Functions adapters
  • Multiple Configurations
  • Inline Validation Rejection
• Stale Data
• Validation
  • Presenters
  • Secrets
• License

💡 Goal

Unifig aims to provides simple and abstract way of handling app's configuration. It allows to load configuration data from multiple sources without changing defined config template. Many templates can be defined to further organize the code eg. MainConfiguration and ModuleConfiguration.

Adapted configuration data is transformed into templates and validated via class-transformer and class-validator. Once initialized configurations can be reloaded without app restart.

Installation

npm i @unifig/core
# or
yarn add @unifig/core

Setting up Templates

Unifig centralizes configuration management in classes called templates. They are resposible for deserializing config values from sources into rich js / ts objects and validating them afterwards.

import { From, Nested } from '@unifig/core';
import { Transform } from 'class-transformer';
import { IsString, IsArray } from 'class-validator';

class DbSettings {
  @From({ key: 'DB_URL', default: 'localhost' })
  @IsString()
  url: string;

  @From('DB_PASSWORD')
  @IsString()
  password: string;

  @From('DB_RECONNECT_DELAYS')
  @Transform(({ value }) => value.split(',').map((n) => Number(n)))
  @IsArray()
  reconnectDelays: number[];
}

Subtemplates

They allow to keep config structure organized by grouping inseparable properties and allowing reusing of them. The subtemplate itself is declared just as regular template, including option to nest further subtemplates in it.

export class AppSettings {
  @From('PORT')
  @IsInt()
  port: number;

  @Nested(() => DbSettings)
  db: DbSettings;
}

Using Configuration

Such defined templates should be loaded before any other action in the application takes place. After that configuration can be accessed from any place in the app via global Config reference.

Quick Start

import { Config, PlainConfigAdapter } from '@unifig/core';

async function bootstrap() {
  const validationError = await Config.register({
    template: AppSettings,
    adapter: async () => ({
      PORT: 3000,
      DB_URL: 'localhost:5467',
      DB_PASSWORD: 'password',
      DB_RECONNECT_DELAYS: '56,98,34,72',
    }),
  });

  if (validationError) {
    console.error(validationError.message);
    process.exit(1);
  }

  const options = Config.getValues(AppSettings);
  console.log(options.port); // output: 3000
  console.log(options.db.url); // output: localhost:5467
}

bootstrap();

Values adapters

Unifig allows to easily swap config values sources or introduce new ones. Implementation of the adapter consist of class which exposes load method, which is called upon config initialization. The method should return dictionary with keys used in @From decorators in templates and underlying values.

import { ConfigAdapter, ConfigSource } from '@unifig/core';

export class CustomAdapter implements ConfigSyncAdapter {
  load(): ConfigSource {
    return {
      PORT: '3000', // will be parsed to number as declared in template
      DB_URL: 'localhost:5467',
      DB_PASSWORD: 'password',
      DB_RECONNECT_DELAYS: '56,98,34,72',
    };
  }
}

Config.registerSync({
  template: AppSettings,
  adapter: new CustomAdapter(),
});

In case of asynchronous way of loading config (like cloud remote configuration service) the adapter needs to implement ConfigAdapter interface.

import { ConfigAdapter, ConfigSource } from '@unifig/core';

export class RemoteConfigAdapter implements ConfigAdapter {
  async load(): Promise<ConfigSource> {
    return { ... };
  }
}

Such adapter requires to be used by async register method.

await Config.register({
  template: AppSettings,
  adapter: new RemoteConfigAdapter(),
});

See full list of adapters here.

Functions Adapters

Alternatively adapter can be defined as standalone sync or async function with same rules applied.

Config.registerSync({
  template: AppSettings,
  adapter: () => ({
    PORT: '3000',
    DB_URL: 'localhost:5467',
    DB_PASSWORD: 'password',
    DB_RECONNECT_DELAYS: '56,98,34,72',
  }),
});

Types Conversion

When loading configuration from predefined objects it's handy to disable the default behavior of implicit properties types conversion.

await Config.register({
  template: AppSettings,
  enableImplicitConversion: false,
  adapter: new CustomAdapter(),
});

Multiple Configurations

In case no single configuration root (AppSettings in above example), templates need to be registered separately.

await Config.register(
  { template: DbSettings, adapter: ... },
  { template: AuthSettings, adapter: ... },
  { templates: [FilesStorageSettings, CacheSettings], adapter: ... },
);

Inline Validation Rejection

To throw validation exception right away after encountering errors instead of returning it use

await Config.registerOrReject({ template: DbSettings, adapter: ... });

Stale Data

Upon changing application's configuration one must be usually restarted to re-fetch new values. Unifig delivers an option to reload registered configurations in real time without app's restart.

await Config.getContainer(Settings).refresh();

Validation

Template errors can be handled in various ways, usually exiting the application early to prevent unexpected behavior.

const validationError = Config.registerSync({ ... });

if (validationError) {
  console.error(validationError.message);
  process.exit(1);
}

Presenters

Message contains list of templates names that failed validation. The errors object contains details about what and why doesn't fullfil requirements. Presenters are to utilize this information in a readable manner.

• Validation presenter: table - 2d table format
• Validation presenter: JSON - JSON string

Secrets

Validation report involves properties values that didn't pass validation. In some cases it's required to hide them. For such cases there is a Secret decorator.

export class DbConfigMock {
  @From('DB_URL')
  @IsString()
  url: string;

  @From('DB_PASSWORD')
  @Secret()
  @IsString()
  password: string;
}

With it applied, password value will be transformed into ****** in potential validation report.

License

This project is licensed under the MIT License - see the LICENSE file for details.