Schema composition breaks with additionalProperties: false

[tariq-tb]

Schema composition doesn't appear to work with additionalProperties: false.

openapi.yaml

openapi: 3.0.1
components:
  schemas:
    Pet:
      type: object
      properties: 
        name:
          type: string
        age:
          type: integer
      required: 
        - name
        - age
      additionalProperties: false
    Dog:
      allOf: 
        - $ref: '#/components/schemas/Pet'
        - type: object
          properties:
            bark:
              type: boolean
          required:
            - bark
      additionalProperties: false
      
paths:
  /simple:
    post:
      requestBody:
        content:
          application/json:
            schema:
              $ref: '#/components/schemas/Pet'
      responses:
        '200':
          content:
            application/json:
              schema:
                type: object
  /complex:
    post:
      requestBody:
        content:
          application/json:
            schema:
              $ref: '#/components/schemas/Dog'
      responses:
        '200':
          content:
            application/json:
              schema:
                type: object

Simple schema

1. Hitting /simple with the following works as expected.

{
    "name": "hunter",
    "age": 12,
}

2. Including an extra property foo in the request...

{
    "name": "hunter",
    "age": 12,
    "foo": true
}

...returns an error as expected because additionalProperties: false is set on the Pet schema.

{
    "error": {
        "name": "ValidationError",
        "message": "Error while validating request: request.body should NOT have additional properties",
        "data": [
            {
                "keyword": "additionalProperties",
                "dataPath": ".body",
                "schemaPath": "#/properties/body/additionalProperties",
                "params": {
                    "additionalProperty": "foo"
                },
                "message": "should NOT have additional properties"
            }
        ]
    }
}

Complex schema with composition

On the other hand, hitting /complex with the following...

{
    "name": "hunter",
    "age": 12,
    "bark": true
}

...returns an unexpected error.

{
    "error": {
        "name": "ValidationError",
        "message": "Error while validating request: request.body should NOT have additional properties",
        "data": [
            {
                "keyword": "additionalProperties",
                "dataPath": ".body",
                "schemaPath": "#/properties/body/additionalProperties",
                "params": {
                    "additionalProperty": "name"
                },
                "message": "should NOT have additional properties"
            }
        ]
    }
}

[keepersmith]

I discovered this as well, and it is more of an issue with OAS than express-openapi-validate.
To get it to work, you need to put in stubs for properties of Pet, and use additionalProperties: false in the object explicity defined in Dog; like so:

Dog:
  allOf: 
    - $ref: '#/components/schemas/Pet'
    - type: object
      properties:
        bark:
          type: boolean
        name: {}
        age: {}
      required:
        - bark
        - name
        - age
      additionalProperties: false

[tariq-tb]

I agree this might not be an issue with express-openapi-validate, just opening up the discussion here, happy to move it elsewhere. Tried your solution, but it did not resolve the issue.

Using your suggestions:

openapi: 3.0.1
components:
  schemas:
    Pet:
      type: object
      properties: 
        name:
          type: string
        age:
          type: integer
      required: 
        - name
        - age
      additionalProperties: false
    Dog:
      allOf: 
        - $ref: '#/components/schemas/Pet'
        - type: object
          properties:
            bark:
              type: boolean
            name: {}
            age: {}
          required:
            - bark
            - name
            - age
          additionalProperties: false
      # additionalProperties: false

...now results in:

{
    "error": {
        "name": "ValidationError",
        "message": "Error while validating request: request.body should NOT have additional properties",
        "data": [
            {
                "keyword": "additionalProperties",
                "dataPath": ".body",
                "schemaPath": "#/properties/body/allOf/0/additionalProperties",
                "params": {
                    "additionalProperty": "bark"
                },
                "message": "should NOT have additional properties"
            }
        ]
    }
}

[thetumper]

If you remove the additionalProperties in the Pet schema, it will no longer complain about bark. Specifying that in Pet conflicts with the set of properties in the Dog schema.

[tariq-tb]

That's correct, but then /simple allows extra properties which isn't ideal.

[thetumper]

True. Workaround would be to have Pet remain "generic" -- only used as ref by other types, which specify additionalProperties: false, and are the ones actually used.

I.e., specify this:

PetConcrete:
      allOf: 
        - $ref: '#/components/schemas/Pet'
        - type: object
          properties:
            name: {}
            age: {}
          additionalProperties: false

and then use PetConcrete for the /simple request body type, not Pet.

[tariq-tb]

Confirmed that your workaround along with @keepersmith's change does work, for better or worse. Updated openapi.yaml below.

components:
  schemas:
    Pet:
      type: object
      properties: 
        name:
          type: string
        age:
          type: integer
      required: 
        - name
        - age
      # additionalProperties: false
    Dog:
      allOf: 
        - $ref: '#/components/schemas/Pet'
        - type: object
          properties:
            bark:
              type: boolean
            name: {}
            age: {}
          required:
            - bark
          additionalProperties: false
    PetConcrete:
      allOf: 
        - $ref: '#/components/schemas/Pet'
        - type: object
          properties:
            name: {}
            age: {}
          additionalProperties: false
paths:
  /simple:
    post:
      requestBody:
        content:
          application/json:
            schema:
              $ref: '#/components/schemas/PetConcrete'
      responses:
        '200':
          content:
            application/json:
              schema:
                type: object
  /complex:
    post:
      requestBody:
        content:
          application/json:
            schema:
              $ref: '#/components/schemas/Dog'
      responses:
        '200':
          content:
            application/json:
              schema:
                type: object