json-expand

Expands your self referencing json

Installation

Standalone Script

$ git clone https://github.com/joshwillik/json-expand.git
$ chmod +x json-expand/json-expand.js
$ mv json-expand/json-expand.js ~/my-scripts/json-expand
# Assuming ~/my-scripts is in $PATH

NPM module

$ npm install -g json-expand

CLI Usage

// config.json
{
  "apiDomain": "api.{{baseDomain}}",
  "baseDomain": "{{userAccount}}.{{hostingProvider}}",
  "userAccount": "joshwillik",
  "hostingProvider": "superhost.foobar",
  "authDomain": "{{google.accounts.base}}{{google.accounts.url}}",
  "google": {
    "accounts": {
      "url": "/login",
      "base": "accounts.google.com"
    }
  }
}

$ json-expand < config.json
{
  "apiDomain": "api.joshwillik.superhost.foobar",
  "baseDomain": "joshwillik.superhost.foobar",
  "userAccount": "joshwillik",
  "hostingProvider": "superhost.foobar",
  "authDomain": "accounts.google.com/login",
  "google": {
    "accounts": {
      "url": "/login",
      "base": "accounts.google.com"
    }
  }
}

Node.js usage

var expand = require( 'json-expand' )
var obj = {
    foo: "bar",
    message: "foo = {{foo}}"
}
expand( obj )
> { foo: 'bar', message: 'foo = bar' }

Rules

Any expression wrapped in {{ }} will be expanded to the correct value or an empty string if none exists. The expression to expand may come before the thing it will expand to.

{
    "name": "John, son of {{parent}}",
    "parent": "Bill"
}
// becomes
{
    "name": "John, son of Bill",
    "parent": "Bill"
}

An expression may reference sub-properties of the document it resides in. All expressions are evaluated starting at the top scope.

{
    "description": "John drives with {{vehicle.wheels}} wheels",
    "vehicle": {
        "wheels":4
    }
}
// becomes
{
    "description": "John drives with 4 wheels",
    "vehicle": {
        "wheels":4
    }
}

Using || operator will make json-expand attempt to expand each option, in order, until one works. Once one value is valid, the rest of the options are ignored.

{
    "description": "I enjoy {{ favoriteFood || foodIKindaLike }}",
    "foodIKindaLike": "spaghetti"
}
// becomes
{
    "description": "I enjoy spaghetti",
    "foodIKindaLike": "spaghetti"
}
// but
{
    "description": "I enjoy {{ favoriteFood || foodIKindaLike }}",
    "foodIKindaLike": "spaghetti",
    "favoriteFood": "meatballs"
}
// becomes
{
    "description": "I enjoy meatballs",
    "foodIKindaLike": "spaghetti",
    "favoriteFood": "meatballs"
}

Environment variables may be substituted by adding a $ before an expression. Using || works just fine with these.

{
    "remoteHost": "{{ $REMOTE_HOST || defaultHost }}",
    "defaultHost": "production.project.com"
}
// if REMOTE_HOST has been set to 'dev.project.com
{
    "remoteHost": "dev.project.com",
    "defaultHost": "production.project.com"
}
// otherwise
{
    "remoteHost": "production.project.com",
    "defaultHost": "production.project.com"
}

Expressions can be concatinated together if desired. The + has higher precedence than ||, so {{ foo || bar + ' test'}} will result in either (foo) or (bar + ' test'), never (foo + ' test').

Using parenthesis to override the order of operations will not work in this version.

{
    "baseDomain": "my-project.com",
    "apiDomain": "{{ doesNotExist || 'api.' + baseDomain }}"
}
// becomes
{
    "baseDomain": "my-project.com",
    "apiDomain": "api.my-project.com"
}