Incorrect Detection of Breaking Change for Default Values

[Krzysztof-Kolodziejczyk]

Incorrect Detection of Breaking Change for Default Values in oasdiff

Description

The oasdiff tool is incorrectly marking the addition of a new required property with a default value in request bodies as a breaking change. According to OpenAPI specifications, if a new required field in the request body schema is assigned a default value, it should not be considered a breaking change because it does not require any changes from the client’s side to maintain compatibility.

Versions

• oasdiff Version: 1.10.9
• OpenAPI Specification Files: Version 1.1 and 1.2

Steps to Reproduce

1. OpenAPI Specification File 1.1 (api-1.1.yaml):

   openapi: 3.0.0
   info:
     title: Order API
     version: '1.1'
   paths:
     /order:
       post:
         summary: Create a new order
         requestBody:
           required: true
           content:
             application/json:
               schema:
                 $ref: '#/components/schemas/Order'
         responses:
           '200':
             description: Order created
   components:
     schemas:
       Order:
         type: object
         properties:
           itemId:
             type: string
   

2. OpenAPI Specification File 1.2 (api-1.2.yaml):

openapi: 3.0.0
info:
title: Order API
version: '1.2'
paths:
/order:
  post:
    summary: Create a new order
    requestBody:
      required: true
      content:
        application/json:
          schema:
            $ref: '#/components/schemas/Order'
    responses:
      '200':
        description: Order created
components:
schemas:
  Order:
    type: object
    properties:
      itemId:
        type: string
      quantity:
        type: number
        default: 0
    required:
      - quantity

3. Run oasdiff on these files:
   Use the following command to compare the two versions of the API specifications:

oasdiff api-1.1.yaml api-1.2.yaml

4. Output

1 breaking changes: 1 error, 0 warning
error   [new-required-request-property] at api-1.2.yaml
    in API POST /order
            added the new required request property 'quantity'