Configuration File System

Not ready for primetime yet. No unit tests. Inspired by rc and acm, both great but I needed some of both.

For the following examples, I'm assuming we're calling the program RESTAPI.

To set a configuration value using an environment variable:

• export RESTAPI_DEMO_CONNECTION_HOST=192.168.1.16

  Translates to OPTIONS.demo.connection.host = '192.168.1.16'

• export RESTAPI_DEMO_CONNECTION_PORT=27017

  Translates to OPTIONS.demo.connection.port = 27017

In the end you end up with the following overrides:

{
    demo: {
        connection: {
            host: '192.168.1.16',
            port: 27017
        }
    } 
}

For setting a single value using RESTAPI. Notice that both '_' and '.' work here:

• export RESTAPI=demo_connection_host=192.168.1.16
• export RESTAPI=demo.connection.port=27017

Or via the command line: --restapi.demo.connection.host=192.168.1.16

Usage

Simply create the instance.

const
     config = new Configuration( 'restapi', { hello: "World", more: { say: "Hi, dude!" } } ),
     options = cfg.get();

console.log( 'All my options merged:', options );
console.log( 'Where did we look?', cfg.diagnostics );

For example, if (on Windows) you have a couple of config files in your path:

In the current directory we have .restapirc

{
    "local": {
        "options": {
            "go": "here",
            "boolean": false
        }
    }
}

and in your home directory you make, for example, restapi.json

{
    "from": {
        "myhome": [ "first", "second" ]
    }
}

and then run the following command (config-test.js is not a real app, just an example. Substitute an actual app):

set RESTAPI_WEE_VALUES=things && set RESTAPI=some.server.elsewhere=192.168.1.16 && node config-test.js --restapi.custom.demo.connection.host=192.168.1.16 --restapi.custom.how.about.two=question

we get the following config

{ 
     hello: 'World',
     more: { 
         say: 'Hi dude!' 
     },
     from: { 
         myhome: [ 'first', 'second' ] 
     },
     local: { 
         options: { 
             go: 'here', 
             boolean: false 
         } 
     },
     some: { 
         server: { 
             elsewhere: '192.168.1.16' 
         } 
     },
     wee: { 
         values: 'things' 
     },
     custom: { 
         demo: { 
             connection: { 
                 host: '192.168.1.16' 
             } 
         },
         how: { 
             about: { 
                 two: 'question' 
             } 
         } 
     } 
 }

If you leave out appName, it will get the application name from the package.json belonging to the top module of the current app.

Configuration values are read in the following order, later reads overwrite ealier ones, so the first step as the lowest priority as it can get overwritten by any of the later steps.

1. Default configuration
2. Configuration files read from /etc
3. Configuration files read from $HOME
4. Configuration files read from process.cwd()
5. Configuration files read from process.cwd() and checking everywhere up to the root
6. Environment variables
7. Command line argunments
8. Internal overrides applied by the code

In the list above, whenever it says "Configuration files read from" it actually tries a number of variations, trying to locate a config file. Basically, it tries all the combinations listed below.

1. Check location for .config/<APPNAME>/config
2. Check for variations: .config/<APPNAME>/config.json, .config/<APPNAME>/config.json5, .config/<APPNAME>/config.ini, .config/<APPNAME>/config.yml, .config/<APPNAME>/config.yaml
3. Check location for .config/<APPNAME>
4. Check for variations: .config/<APPNAME>.json, .config/<APPNAME>.json5, .config/<APPNAME>.ini, .config/<APPNAME>.yml, .config/<APPNAME>.yaml
5. Check location for .<APPNAME>/config
6. Check for variations: .<APPNAME>/config.json, .<APPNAME>/config.json5, .<APPNAME>/config.ini, .<APPNAME>/config.yml, .<APPNAME>/config.yaml
7. Check location for .<APPNAME>rc
8. Check for variations: .<APPNAME>rc.json, .<APPNAME>rc.json5, .<APPNAME>rc.ini, .<APPNAME>rc.yml, .<APPNAME>rc.yaml
9. Check location for <APPNAME>
10. Check for variations: <APPNAME>.json, <APPNAME>.json5, <APPNAME>.ini, <APPNAME>.yml, <APPNAME>.yaml

To see the complete list, look at the diagnostics field of the Configuration class. There you can find the entire list of all the files it checked for, as well as the files actually loaded.