An Extensible Wrapper for Node Config

release notes

Introduction

An extensible wrapper of the popular config package, supporting:

• placeholder resolution (or variable expansion),
• encrypted values (via jasypt)
• default (or fallback) values,
• and optional asynchronous url fetching.

Usage

To use the module, substitute the named {config} module export, in place of the popular config default – note, we use named exports, because the module exports other useful classes as well.

import  { config } from '@alt-javascript/config' ;

config.get('key');
config.get('nested.key');
config.get('unknown','use this instead'); // this does not throw an error

Config values that include the common ${placeholder} syntax, will resolve the inline placeholders, so the config.get('placeholder')' path below will return start.one.two.end.

Config values that start with the prefix enc. will be decrypted with the jasypt package port, with the passphrase being sourced from the process.env.NODE_CONFIG_PASSPHRASE environment variable.

Optionally, config values that start with the prefix url. can be fetched and resolved asynchronously with the fetch function, and HTTP options can be specified as in the example config file. To avoid bundling node-fetch, you need to provide it by using @alt-javascript/boot to boot it into the global root context, where the package will detect it.

import { boot } from '@alt-javascript/boot';
import { config } from '@alt-javascript/config';
import fetch from 'node-fetch';

boot({config,fetch})
const webdata = await config.fetch('pathToUrlPrefixedValue'); 

:warning: While we have implemented asynchronous fetch from "the network", we discourage it.

It's mostly a design flex.

Configuration should be static and immutable contextual information your system needs on application bootstrap, and configuration as a service increases the complexity of your deployment architecture, making it difficult to configure different, and ephemeral deployment options, including local development and testing.

Don't say we didn't warn you.

local-development.json

{
  "key": "value",
  "one" : "one",
  "placeholder": "start.${one}.${nested.two}.end",
  "placeholderEncrypted": "start.${nested.encrypted}.end",
  "nested" : {
    "key" : "value",
    "two" : "two",
    "placeholder": "start.${one}.${nested.two}.end",
    "encrypted" : "enc.pxQ6z9s/LRpGB+4ddJ8bsq8RqELmhVU2",
    "encryptedWithSecret" : "enc./emLGkD3cbfqoSPijGZ0jh1p1SYIHQeJ"
  },
  "jsonplaceholder": {
    "todos": "url.https://jsonplaceholder.typicode.com/todos/1"
  },
  "fetchWithOpts" : {
    "url": "url.https://jsonplaceholder.typicode.com/todos/1",
    "authorization": "Basic dXNlcjpwYXNz",
    "method": "get",
    "body": {},
    "headers": {"Content-Type": "application/json"}
  }
}

Browser

The module is also able to be used directly in the browser, in combination with the config module. You can either import the LoggerFactory globally as an IIFE (Immediately Invoked Function Expression), as follows:

   <script src="https://cdn.jsdelivr.net/npm/@alt-javascript/config/dist/alt-javascript-configfactory-iife.js"></script>
   <script>
       var config = ConfigFactory.getConfig({
           logging : {
               format : 'json',
               level : {
                   '/' : 'info',
                   '/MyPage': 'info'
               }
           }
           "http://127+0+0+1:8080" : {
               logging : {
                   format : 'json',
                   level : {
                       '/' : 'info',
                       '/MyPage' : 'debug'
                   }
               }             
           }

       })
       var logger = LoggerFactory.getLogger('/MyPage',config);
       logger.debug('Hello World');
   </script>

Or import the ES6 module bundle from a module, as follows:

import { ConfigFactory } from 'https://cdn.jsdelivr.net/npm/@alt-javascript/logger/dist/alt-javascript-config-esm.js'

//...as above

Encrypted config is not supported in the browser (by default), as it is inherently unsecure (there is no safe way to hide the salt).

Additionally, config sections can be prefixed with the window location to allow site or environment specific configuration in the browser (periods must be replaced with a plus sign - so mysite.com => mysite+com).

Testability

Testing config is hard, and testability is a first class concern at @alt-javascript so the config wrapper, and the module exports an EphemeralConfig that can source config paths from a plain old javascript object as follows, allowing you to assert varying configurations easily

import {
    EphemeralConfig, ValueResolvingConfig, PlaceHolderResolver, PlaceHolderSelector
    
} from '@alt-javascript/config';

const ephemeralConfig = new EphemeralConfig({
    key: 'value',
    nested: {
        key: 'value',
    },
});

const placeHolderResolver = new PlaceHolderResolver(new PlaceHolderSelector());
const config = new ValueResolvingConfig(ephemeralConfig,placeHolderResolver );

License

May be freely distributed under the MIT license.

Copyright (c) 2021 Craig Parravicini