reverse-config

reverse-config

Reverse npm package config environment variables into an object.

Installation

$ npm install reverse-config

reverse-config, What is it Good For?

• use built in npm functionality instead of homegrown configuration formats and parsers
• selectively override configuration for local development in your ~/.npmrc

Essentially, this package is just syntactic sugar for reading npm_package_config_* properties from process.env.

Usage

var reverseConfig = require('reverse-config');
reverseConfig.get({string} [key])

• if key is undefined, the entire configuration object is returned
• if key is alphanumeric, it is used as property accessor for the configuration object
• otherwise
  • all non-alphanumeric characters are replaced by underscores
  • consecutive underscores are collapsed to a single one
  • leading and trailing underscores are stripped
  • the remaining value is split with the underscore and used as a 'deep' property accessor
    • example: .get('@my.scoped/package') would try to access .my.scoped.message in the configuration object

Gotchas

The npm transformation of the package.json config object to environment variables is a destructive process.

Given either

{
  "config": {
    "foo": [
      42
    ]
  }
}

or

{
  "config": {
    "foo": {
      "0": 42
    }
  }
}

or

{
  "config": {
    "foo_0": "42"
  }
}

the resulting environment variable name is npm_package_config_foo_0, and its value the string '42'.

Rule of thumb: only use alphanumeric property names.

The useful exception would be package names used as config sections, e.g.

{
  "config": {
    "my_package": {},
    "@my.scope/my-package": {},
  }
}

Use with moderation and pretend to be a responsible adult.

Values

During reversion values are coerced with good faith as follows:

• numeric string => {number}
• 'true' => {boolean} true
• 'false' => {boolean} false
• 'null' => {null} null

In other words, you might face surprises if you use strings like "42", "true", "false" or "null" as property values in your package.json config object. Don't do that then!.

License

MIT