Environment-override NPM

Environment Override

Takes an object holding configuration and checks the environment variables for overrides to its values. Great for hapi manifests and other types of configuration.

How to use

The code is currently synchronous as its expected to only be run once as part of the startup of the app.

In code

var override = require('environment-override').override;
var manifest = require('./manifest.json');
override(manifest, 'PREFIX_');

Command line

environment-override ships with an utility that can show you all the variables from a json file that can be overridden via environment variables:

node ./node_modules/environment-override/bin/show test.json

To avoid polluting the environment you can set a prefix for the variables:

node ./node_modules/environment-override/bin/show test.json -p PREFIX_

It can also show the original and overridden versions:

node ./node_modules/environment-override/bin/show test.json -o diff

The output can be:

diff - Shows the diff between the two versions.
all - Shows both the original and the overridden versions.
original - Shows the original version.
current - Shows the overridden version.

Removing values

To remove a value set the entry to OVERRIDE_REMOVE_DATA in the environment.

Whole structures

To override whole structures use a stringified JSON object in the variable:

exports PREFIX_VARIABLE='{"key1": "value1", "key2": "value2"}'

Example

Assuming we have the following test.json file:

{
  "field1": "value1",
  "field2": {
    "s1": "v1",
    "s2": "v2"
  },
  "field3": "value3"
}

We can see all the variables by running show.js:

./bin/show.js test.json -p APP_                              
INFO: Using the prefix "APP_" you have the following overrides:
		APP_FIELD1
    APP_FIELD2
    APP_FIELD2_S1
    APP_FIELD2_S2
    APP_FIELD3

We can override them by setting various values:

export APP_FIELD1 = 'updated1'
export APP_FIELD2 = '{"s1": "updated_f2_value1", "s2": "updated_f2_value2"}';
export APP_FIELD3 = 'OVERRIDE_REMOVE_DATA'

Running show.js again will inform us of which variables were overridden:

./bin/show.js test.json -p APP_                                      
INFO: Using the prefix "APP_" you have the following overrides:
  overridden APP_FIELD1
  overridden APP_FIELD2
     removed APP_FIELD3

We can also get a diff: