json-schema-deref

Dereference JSON pointers in a JSON schemas with their true resolved values. A lighter synchronous version of this module is available as json-schema-deref-sync, but omits web references and custom loaders.

Installation

npm install json-schema-deref

Overview

Let's say you have the following JSON Schema:

{
  "description": "Just some JSON schema.",
  "title": "Basic Widget",
  "type": "object",
  "definitions": {
    "id": {
      "description": "unique identifier",
      "type": "string",
      "minLength": 1,
      "readOnly": true
    }
  },
  "properties": {
    "id": {
      "$ref": "#/definitions/id"
    },
    "foo": {
      "$ref": "http://www.mysite.com/myschema.json#/definitions/foo"
    },
    "bar": {
      "$ref": "bar.json"
    }
  }
}

Sometimes you just want that schema to be fully expanded, with $ref's being their (true) resolved values:

{
  "description": "Just some JSON schema.",
  "title": "Basic Widget",
  "type": "object",
  "definitions": {
    "id": {
      "description": "unique identifier",
      "type": "string",
      "minLength": 1,
      "readOnly": true
    }
  },
  "properties": {
    "id": {
      "description": "unique identifier",
      "type": "string",
      "minLength": 1,
      "readOnly": true
    },
    "foo": {
      "description": "foo property",
      "readOnly": true,
      "type": "number"
    },
    "bar": {
      "description": "bar property",
      "type": "boolean"
    }
  }
}

This utility lets you do that:

var deref = require('json-schema-deref');
var myschema = require('schema.json');

deref(myschema, function(err, fullSchema) {
  console.dir(fullSchema); // has the full expanded $refs
});

API Reference

deref(schema, options, fn)

Derefs $ref's in JSON Schema to actual resolved values. Supports local, file and web refs.

Kind: global function

Param	Type	Description
schema	Object	The JSON schema
options	Object	options
options.baseFolder	String	the base folder to get relative path files from. Default is process.cwd()
options.cache	String	whether to cache the result from the request. Default: true.
options.cacheTTL	Number	the time to keep request result in cache. Default is 5 minutes.
options.failOnMissing	Boolean	By default missing / unresolved refs will be left as is with their ref value intact. If set to true we will error out on first missing ref that we cannot resolve. Default: false.
options.loader	function	a function for custom loader. Invoked if we could not resolve the ref type, or if there was an error resolving a web or file ref types. function with signature: function(refValue, options, fn) refValue - the string value of the ref being resolved. Ex: db://my_database_id options - options parameter passed to deref fn - the final callback function, in form function(err, newValue) err - error if ref is valid for the loader but there was an error resolving the ref. If used in combination with failOnMissing option it will abort the whole deref process. newValue - the resolved ref value, or null or undefined if the ref isn't for this custom loader and we should just leave the $ref as is.
fn	function	The final callback in form (error, newSchema)

Custom Loader

Let's say we want to get $ref's from a MongoDB database, and our $ref objects in the JSON Schema might be something like:

"foo": {
  "$ref":"mongodb:507c35dd8fada716c89d0013"
}

Our custom loader function passed in the options loader parameter would look something like:

function myMongoDBLoader(ref, option, fn) {
  if(ref.indexOf('mongodb:') === 0) {
    var id = ref.substring(8);
    return collection.findOne({_id:id}, fn);
  }

  // not ours, pass back nothing to keep it the same
  // or pass error and use failOnMissing to abort
  return fn();
}