XML example cannot be generated with 'allOf'

Look an example:

openapi: '3.0.0'
info:
  version: 1.0.0
  title: example
servers:
  - url: http://localhost:80

paths:
  /books:
    post:
      summary: add a book
      requestBody:
        content:
          application/xml:
            schema:
              description: book to be added
              allOf:
                - $ref: '#/components/schemas/book'
      responses:
        '200':
          description: OK
components:
  schemas:
    book:
      description: a book
      type: object
      properties:
        id:
          type: string
        author:
          type: string
        year:
          type: integer
          format: int32

Then if I click the ‘Example Value’ in swagger ui, it gives this info:

<?xml version="1.0" encoding="UTF-8"?>
<!-- XML example cannot be generated -->

However, if I remove ‘allOf’:

openapi: '3.0.0'
info:
  version: 1.0.0
  title: example
servers:
  - url: http://localhost:80

paths:
  /books:
    post:
      summary: add a book
      requestBody:
        content:
          application/xml:
            schema:
              $ref: '#/components/schemas/book'
      responses:
        '200':
          description: OK
components:
  schemas:
    book:
      description: a book
      type: object
      properties:
        id:
          type: string
        author:
          type: string
        year:
          type: integer
          format: int32

It shows example value correctly:

<?xml version="1.0" encoding="UTF-8"?>
<book>
	<id>string</id>
	<author>string</author>
	<year>0</year>
</book>

And if I change application format to json, it shows json example value correctly whether there is allOf or not.

The reason I want to use allOf is for this.

So is this a bug of allOf or an expected behaviour?
If it’s an expected behaviour, then how to solve this two problems?

Currently, I’m using Swagger Editor online version in Chrome browser.

This issue seems related.

[heldersepu]

Sounds like a good time to kick XML out your API !

Sorry I know is not helpful, I just could not resist…

[kalatchev]

Same issue 😦 Enterprise APIs relay on XML. JSON is primary for web development. XML can be transformed with XSLT, data can be found with XPath and defined with XSD. JSON … OMG! Do you know any bank or health system, which works with JSON? I mean in core of systems, not web site integrations? Common, XML is here to stay for a long time.