@gasket/plugin-config

Supports application-specific (non-Gasket plugin) configuration.

This plugin assembles a configuration for your environment from config file(s) which is then exposed the configuration to server-side code and can be accessible via Redux.

Installation

New apps

gasket create <app-name> --plugins @gasket/plugin-config

Existing apps

npm i @gasket/plugin-config

Modify plugins section of your gasket.config.js:

module.exports = {
  plugins: {
    add: [
+      '@gasket/plugin-config'
    ]
  }
}

Usage

There are two file structure methods available for defining config of different environments in apps.

1. Multiple files with Environment per file
2. Single file with Environments inline

Environment files

By default, this plugin imports files from your /config directory to assemble your application's config. You can change this directory with the configPath option in your gasket.config.js:

module.exports = {
  configPath: './src/config'
};

Gasket first decides which environment you're running in. By default, this comes from the NODE_ENV environment variable or the --env command-line argument which can be set from the GASKET_ENV environment variable. Environments can be sub-divided (say, for multiple data centers) through dotted identifiers. Example: production.v1.

Once this environment identifier is determined, files are imported based on the identifier and deep merged together. Files must be CommonJS .js modules or .json files with the name of your environment. You may optionally have a base.js[on] file shared across all environments. Given the example environment production.v1, the following files may be merged together:

production.v1.js
production.js
base.js

If you run your application via gasket local or explicitly set your environment to local, there's additional merging behavior:

local.overrides.js
local.js
development.js (or dev.js)
base.js

The optional local.overrides.js is something that can be on individual workstations and ignored in your .gitignore. Depending on if you're naming your development environment dev or development, that will automatically be merged with your local configuration.

Environments inline

Additionally, you can optionally add an app.config.js file to the root of your app's directory, alongside the gasket.config.js. This config file allows you to set up inline environment overrides, as opposed to in separate files, following the same rules as the gasket.config.js.

If you happen to set up config in both ./config and app.config.js, the configurations will be merged with ./config taking priority. The .json extension is also supported for this file.

To support easy local development, you can use an app.config.local.js which will merge in your own local configuration for development. This file should not be committed, and specified in .gitignore.

Accessing Config

The plugin attaches the configuration from your config files to a config property of the Request object.

Example with Next.js

If you are developing a front end with Next.js, config is accessible to server-side rendering via getInitialProps:

import * as React from 'react';

export default PageComponent extends React.Component {
  static getInitialProps({ isServer, req }) {
    if (isServer) {
      return {
        flags: req.config.featureFlags
      };
    }
  }

  // ...
}

Example with Middleware

Custom Express middleware (provided you ensure that your middleware runs after the config plugin). For example, in /lifecycles/middleware.js:

module.exports = {
  timing: { after: ['@gasket/config'] },
  handler(gasket) {
    return (req, res, next) => {
      if (req.config.featureFlags.betaSite) {
        res.redirect(req.config.betaSiteURL);
      } else {
        next();
      }
    }
  }
}

Config with Redux

If you need access to config values in client-side code, this can be done through your redux store. The config plugin looks for a redux property of your configuration in app.config.js and places it under a config property in your initial redux state. Example below can selected from state.config.url in client-side code

module.exports = {
  environments: {
    dev: {
      redux: {
        url: 'https://your-dev-service-endpoint.com'
      }
    },
    test: {
      redux: {
        url: 'https://your-test-service-endpoint.com'
      }
    }
  }
};

Config with Public config

If you are not using Redux, but still need access to config values in client-side code, you can define a public property in your app.config.js.

module.exports = {
  public: {
    test1: 'config value 1 here',
    test2: 'config value 2 here'
  }
};

The config plugin will return these public properties to your browser, to be accessed by @gasket/data. They are available as properties on .config and used like so:

import gasketData from '@gasket/data';

console.log(gasketData.config.test1); // config value 1 here

Lifecycles

appEnvConfig

The appEnvConfig event is fired once the config file contents are normalized. Hooks are passed the gasket API and the current configuration and should return a new configuration object with injected modifications. This event will occur once during startup, and hooks may be asynchronous. Sample:

const fetchRemoteConfig = require('./remote-config');

module.exports = {
  hooks: {
    async appEnvConfig(gasket, config) {
      const remoteCfg = await fetchRemoteConfig();

      return {
        ...config,
        ...remoteCfg
      };
    }
  }
}

appRequestConfig

On each request, the appRequestConfig event is fired, enabling plugins to inject configuration derived from the request being processed. It is passed the gasket API, the config, and the Express request & response. Again, hooks should return a new object instead of mutating an existing object. This is especially vital in the case of this event to avoid cross-request information leaks. Sample:

const getFeatureFlags = require('./feature-flags');

module.exports = {
  hooks: {
    async appRequestConfig(gasket, config, req, res) {

      const featureFlags = await getFeatureFlags({
        shopperId: req.user.shopperId,
        locale: req.cookies.market,
        plid: req.user.resellerId
      });

      return {
        ...config,
        featureFlags
      };
    }
  }
}

License

MIT