@stoplight/json-ref-resolver

What is @stoplight/json-ref-resolver?

@stoplight/json-ref-resolver is a utility for resolving JSON references ($ref) in JSON documents. It helps in dereferencing and bundling JSON schemas or other JSON documents that contain references to other documents or internal references.

What are @stoplight/json-ref-resolver's main functionalities?

Dereferencing JSON References

This feature allows you to resolve internal JSON references within a document. The example shows how a reference to '#/bar' is resolved to the actual content of 'bar'.

const { resolve } = require('@stoplight/json-ref-resolver');

const document = {
  "foo": { "$ref": "#/bar" },
  "bar": { "baz": 123 }
};

resolve(document).then(result => {
  console.log(result);
  // Output: { foo: { baz: 123 }, bar: { baz: 123 } }
});

Resolving External JSON References

This feature allows you to resolve external JSON references by fetching the referenced document from a URL. The example shows how a reference to an external URL is resolved.

const { resolve } = require('@stoplight/json-ref-resolver');

const document = {
  "foo": { "$ref": "http://example.com/bar.json" }
};

resolve(document).then(result => {
  console.log(result);
  // Output will depend on the content of http://example.com/bar.json
});

Custom Resolvers

This feature allows you to define custom resolvers for handling specific types of references. The example shows how to create a custom resolver for a 'custom://' scheme.

const { resolve } = require('@stoplight/json-ref-resolver');

const customResolver = {
  canRead: (file) => file.url.startsWith('custom://'),
  read: (file) => Promise.resolve({ custom: 'data' })
};

const document = {
  "foo": { "$ref": "custom://example" }
};

resolve(document, { resolvers: [customResolver] }).then(result => {
  console.log(result);
  // Output: { foo: { custom: 'data' } }
});

Other packages similar to @stoplight/json-ref-resolver

json-schema-ref-parser

json-schema-ref-parser is a powerful library for parsing, resolving, and dereferencing JSON Schema $ref pointers. It supports both internal and external references and provides similar functionality to @stoplight/json-ref-resolver. However, it is more focused on JSON Schema specifically.

json-ref-lite

json-ref-lite is a lightweight library for resolving JSON references. It is simpler and has fewer features compared to @stoplight/json-ref-resolver, making it suitable for basic use cases where performance and simplicity are priorities.

json-refs

json-refs is another library for resolving JSON references. It provides a comprehensive set of features for both internal and external references, similar to @stoplight/json-ref-resolver. It also includes additional utilities for working with JSON references.

README

JSON Ref Resolver

Follow $ref values in JSON Schema, OpenAPI (formerly known as Swagger), and any other objects with $ref values inside of them.

• View the changelog: Releases

Features

• Performant: Hot paths are memoized, remote URIs are resolved concurrently, and the minimum surface area is crawled and resolved.
• Caching: Results from remote URIs are cached.
• Immutable: The original object is not changed, and structural sharing is used to only change relevant bits. example test
• Reference equality: $refs to the same location will resolve to the same object in memory. example test
• Flexible: Bring your own readers for http://, file://, mongo://, custom://... etc, or use one of ours.
• Cross Platform: Supports POSIX and Windows style file paths.
• Reliable: Well tested to handle all sorts of circular reference edge cases.

Installation

Supported in modern browsers and node.

yarn add @stoplight/json-ref-resolver

Usage

All relevant types and options can be found in src/types.ts.

// Import the Resolver class.
import { Resolver } from "@stoplight/json-ref-resolver";

/**
 * Create a Resolver instance. Resolve can be called on this instance multiple times to take advantage of caching.
 *
 * @param globalOpts {IResolverOpts} [{}]
 *
 * These options are used on every resolve call for this resolver instance.
 *
 * See `IResolverOpts` interface defined in [src/types.ts](src/types.ts) for available options.
 *
 * @return IResolver
 */
const resolver = new Resolver(globalOpts);

/**
 * Resolve the passed in object, replacing all references.

 * @param resolveOpts {any} - The object to resolve.

 * @param resolveOpts {IResolveOpts} [{}]
 *
 * These options override any globalOpts specified on the resolver instance, and only apply during this resolve call.
 *
 * See `IResolveOpts` interface defined in [src/types.ts](src/types.ts) for available options.
 *
 * @return IResolveResult - see [src/types.ts](src/types.ts) for interface definition.
 */
const resolved = await resolver.resolve(sourceObj, resolveOpts);

Example: Basic Inline Dereferencing

By default, only inline references will be dereferenced.

import { Resolver } from "@stoplight/json-ref-resolver";

const resolver = new Resolver();
const resolved = await resolver.resolve({
  user: {
    $ref: "#/models/user"
  },
  models: {
    user: {
      name: "john"
    }
  }
});

// ==> result is the original object, with local refs resolved and replaced
expect(resolved.result).toEqual({
  user: {
    name: "john"
  },
  models: {
    user: {
      name: "john"
    }
  }
});

Example: Dereference a Subset of the Source

This will dereference the minimal number of references needed for the given target, and return the target.

In the example below, the address reference (https://slow-website.com/definitions#/address) will NOT be dereferenced, since it is not needed to resolve the #/user jsonPointer target we have specified. However, #/models/user/card IS dereferenced since it is needed in order to full dereference the #/user property.

import { Resolver } from "@stoplight/json-ref-resolver";

const resolver = new Resolver();
const resolved = await resolver.resolve(
  {
    user: {
      $ref: "#/models/user"
    },
    address: {
      $ref: "https://slow-website.com/definitions#/address"
    },
    models: {
      user: {
        name: "john",
        card: {
          $ref: "#/models/card"
        }
      },
      card: {
        type: "visa"
      }
    }
  },
  {
    jsonPointer: "#/user"
  }
);

// ==> result is the target object, with refs resolved and replaced
expect(resolved.result).toEqual({
  name: "john",
  card: {
    type: "visa"
  }
});

Example: Dereferencing Remote References with Resolvers

By default only inline references (those that point to values inside of the original object) are dereferenced.

In order to dereference remote URIs (file, http, etc) you must provide resolvers for each URI scheme.

Resolvers are keyed by scheme, receive the URI to fetch, and must return the fetched data.

import { Resolver } from "@stoplight/json-ref-resolver";

// some example http library
import * as axios from "axios";

// if we're in node, we create a file resolver with fs
import * as fs from "fs";

// create our resolver instance
const resolver = new Resolver({
  // resolvers can do anything, so long as they define an async read function that resolves to a value
  resolvers: {
    // this resolver will be invoked for refs with the https protocol
    https: {
      async resolve(ref: uri.URI) {
        return axios({
          method: "get",
          url: String(ref)
        });
      }
    },

    // this resolver will be invoked for refs with the file protocol
    file: {
      async resolve(ref: uri.URI) {
        return fs.read(String(ref));
      }
    }
  }
});

const resolved = await resolver.resolve({
  definitions: {
    someOASFile: {
      $ref: "./main.oas2.yml#/definitions/user"
    },
    someMarkdownFile: {
      $ref: "https://foo.com/intro.md"
    }
  }
});

// ==> result is the original object, with refs resolved and replaced
expect(resolved.result).toEqual({
  definitions: {
    someOASFile: {
      // ... the data located in the relative file `./main.oas2.yml` and inner json path `#/definitions/user`
    },
    someMarkdownFile: {
      // ... the data located at the url `https://foo.com/intro.md`
    }
  }
});

Example: Dereferencing Relative Remote References with the baseUri Option

If there are relative remote references (for example, a relative file path ../model.json), then the location of the source data must be specified via the baseUri option. Relative references will be dereferenced against this baseUri.

import { Resolver } from "@stoplight/json-ref-resolver";
import * as fs from "fs";
import * as URI from "urijs";

const resolver = new Resolver({
  readers: {
    file: {
      async read(ref: uri.URI) {
        return fs.read(String(ref));
      }
    }
  }
});

const sourcePath = "/specs/api.json";
const sourceData = fs.readSync(sourcePath);
// sourceData === {
//   user: {
//     $ref: "../models/user.json"
//   }
// }

const resolved = await resolver.resolve(sourceData, {
  // Indicate where the `sourceData` being resolved lives, so that relative remote references can be fetched and resolved.
  baseUri: new URI(sourcePath)
});

expect(resolved.result).toEqual({
  user: {
    // ... the user object defined in `../models/user.json`
  }
});

In the above example, the user $ref will resolve to /models/user.json, because ../models/user.json is resolved against the baseUri of the current document (which was indicated at /specs/api.json). Relative references will not work if the source document has no baseUri set.

This is a simplistic example of a reader. You can create your own, but we have built some readers which you might find useful.

Contributing

If you are interested in contributing to Spectral itself, check out our contributing docs to get started.