allof-merge

Merge schemas using allOf into a more readable composed schema free from allOf.

Features

• Safe merging of schemas combined with allOf in whole JsonSchema based document
• Fastest implmentation - up to x4 times faster then other popular libraries
• Merged schema does not validate more or less than the original schema
• Removes almost all logical impossibilities
• Correctly merge additionalProperties, patternProperties and properties taking into account common validations
• Correctly merge items and additionalItems taking into account common validations
• Supports rules extension to merge other document types and JsonSchema versions
• Supports $refs and circular references either (internal references only)
• Correctly merge of $refs with sibling content (optionally)
• Correctly merge of combinaries (anyOf, oneOf) with sibling content (optionally)
• Typescript syntax support out of the box
• No dependencies (except json-crawl), can be used in nodejs or browser

Works perfectly with specifications:

• JsonSchema
• OpenApi 3.x
• Swagger 2.x (roadmap)
• AsyncApi 2.x (roadmap)

Other libraries

There are some libraries that can merge schemas combined with allOf. One of the most popular is mokkabonna/json-schema-merge-allof, but it has some limitatons: Does not support circular $refs and no Typescript syntax out of the box.

External $ref

If schema contains an external $ref, you should bundle it via api-ref-bundler first.

Installation

npm install allof-merge --save

Usage

Nodejs

import { merge } from 'allof-merge'

const data = {
  type: ['object', 'null'],
  additionalProperties: {
    type: 'string',
    minLength: 5
  },
  allOf: [{
    type: ['array', 'object'],
    additionalProperties: {
      type: 'string',
      minLength: 10,
      maxLength: 20
    }
  }]
}

const onMergeError = (msg) => {
  throw new Error(msg)
}

const merged = merge(data, { onMergeError })

console.log(merged)
// {
//   type: 'object',
//   additionalProperties: {
//     type: 'string',
//     minLength: 10,
//     maxLength: 20
//   }
// }

Browsers

A browser version of allof-merge is also available via CDN:

<script src="https://cdn.jsdelivr.net/npm/allof-merge@latest/browser/allof-merge.min.js"></script>
<script src="https://cdn.jsdelivr.net/npm/allof-merge@latest/browser/allof-merge.js"></script>

Reference allof-merge.min.js in your HTML and use the global variable AllOfMerge.

<script>
  var merged = AllOfMerge.merge({ /* ... */ })
</script>

Documentation

merge(data: any, options?: MergeOptions)

Create a copy of data with merged allOf schemas:

Merge options

interface MergeOptions {
  // source document if merging only part of it
  // (optional) default = data
  source?: any          
  
  // custom merge rules
  // (optional) default = jsonSchemaMergeRules("draft-06")
  rules?: MergeRules    

  // merge $ref with sibling content
  // (optional) default = false
  mergeRefSibling?: boolean  

  // merge anyOf/oneOf with sibling content
  // (optional) default = false
  mergeCombinarySibling?: boolean  

  // Merge error hook, called on any merge conflicts
  onMergeError?: (message: string, path: JsonPath, values: any[]) => void
}

Supported rules

You can find supported rules in the src/rules directory of this repository:

• jsonSchemaMergeRules(version: "draft-04" | "draft-06")
• openapiMergeRules(version: "3.0.x" | "3.1.x")

Benchmark

allof-merge x 800 ops/sec ±2.35% (90 runs sampled)
json-schema-merge-allof x 217 ops/sec ±2.03% (86 runs sampled)
Fastest is allof-merge

Check yourself:

npm run benchmark

Contributing

When contributing, keep in mind that it is an objective of allof-merge to have no additional package dependencies.

Please run the unit tests before submitting your PR: npm test. Hopefully your PR includes additional unit tests to illustrate your change/modification!

License

MIT