Ignores field-based discrimators

[SteveDunn]

What are you generating using Kiota, clients or plugins?

API Client/SDK

In what context or format are you using Kiota?

Nuget tool

Client library/SDK language

Csharp

Describe the bug

The schema I'm using uses oneOf and relies on required fields to discriminate between one or the other.

However, when deserializing, it does not take these into account.

Expected behavior

It should consider required fields to discriminate between one type or another in oneOf's

How to reproduce

Use the openapi yaml file below. Generate models and classes from it, and the deserialize this json:

{
  "registration": "LF24AVX",
  "make": "RENAULT",
  "model": "CLIO TECHNO TCE",
  "fuelType": "Petrol",
  "primaryColour": "Grey",
  "registrationDate": "2024-06-05",
  "manufactureDate": "2024-06-05",
  "manufactureYear": "2024",
  "motTestDueDate": "2027-06-04",
  "hasOutstandingRecall": "Unknown"
}

Since it doesn't have an motTests node (line 286 in the schema) - it should discriminated against the type VehicleWithMotResponse

Open API description file

openapi: 3.0.0
info:
  title: MOT history API

  version: 1.0.0

servers:
  - url: https://history.mot.api.gov.uk
    description: API URL

security:
  - bearerAuth: []
    apiKey: []

paths:
  /v1/trade/vehicles/registration/{registration}:
    get:
      tags:
        - mot-history-api
      summary: Get MOT tests for a single vehicle by registration number
      description: |-
        ```
        GET /v1/trade/vehicles/registration
        ```
      parameters:
        - $ref: '#/components/parameters/RegistrationParam'
      responses:
        '200':
          $ref: '#/components/responses/VehicleByRegistrationResponse'
        '400':
          $ref: '#/components/responses/400BadRequest'
        '404':
          $ref: '#/components/responses/404NotFound'
        '500':
          $ref: '#/components/responses/500InternalServerError'

  /v1/trade/vehicles/vin/{vin}:
    get:
      tags:
        - mot-history-api
      summary: Get MOT Tests for a single vehicle by vehicle identification number
      description: |-
        ```
        GET /v1/trade/vehicles/vin/
        ```
      parameters:
        - $ref: '#/components/parameters/VinParam'
      responses:
        '200':
          $ref: '#/components/responses/VehicleByVinResponse'
        '400':
          $ref: '#/components/responses/400BadRequest'
        '404':
          $ref: '#/components/responses/404NotFound'
        '500':
          $ref: '#/components/responses/500InternalServerError'

  /v1/trade/vehicles/bulk-download:
    get:
      tags:
        - mot-history-api
      summary: Get MOT history in bulk
      description: |-
        ```
        GET /v1/trade/vehicles/bulk-download
        ```

        Although this endpoint does not yet contain full details for heavy vehicles, some heavy vehicle data may be returned in the response.
      responses:
        '200':
          $ref: '#/components/responses/BulkDownloadResponse'
        '500':
          $ref: '#/components/responses/500InternalServerError'

  /v1/trade/credentials:
    put:
      tags:
        - mot-history-api
      summary: Request a new client secret
      description: |-
        ```
        PUT: /v1/trade/credentials
        ```
        Request a new client secret
      requestBody:
        content:
          application/json:
            schema:
              $ref: '#/components/schemas/RenewCredentialsRequest'
      responses:
        '200':
          $ref: '#/components/responses/RenewCredentialsResponse'
        '400':
          $ref: '#/components/responses/400BadRequest'
        '404':
          $ref: '#/components/responses/404NotFound'
        '412':
          $ref: '#/components/responses/412PreconditionFailed'
        '500':
          $ref: '#/components/responses/500InternalServerError'

components:
  responses:
    VehicleByRegistrationResponse:
      description: |-
        - The registration matches either a vehicle with MOT tests or new registered vehicle and is provided in the response body
      content:
        application/json:
          schema:
            oneOf:
              - $ref: '#/components/schemas/VehicleWithMotResponse'
              - $ref: '#/components/schemas/NewRegVehicleResponse'

    VehicleByVinResponse:
      description: |-
        - The vehicle identification number matches either a vehicle with MOT tests or new registered vehicle and is provided in the response body
      content:
        application/json:
          schema:
            oneOf:
              - $ref: '#/components/schemas/VehicleWithMotResponse'
              - $ref: '#/components/schemas/NewRegVehicleResponse'

    BulkDownloadResponse:
      description: |-
        - The file details and URLs required to download MOT history data in bulk
      content:
        application/json:
          schema:
            $ref: '#/components/schemas/BulkDownloadResponse'

    RenewCredentialsResponse:
      description: |-
        - The email address and API Key Value matches user found in the database and successfully returns new credentials
      content:
        application/json:
          schema:
            $ref: '#/components/schemas/RenewCredentialsResponse'

    400BadRequest:
      description: |-
        - The format of the request is incorrect
      content:
        application/json:
          schema:
            $ref: '#/components/schemas/ErrorResponse'

    404NotFound:
      description: |-
        - The requested data is not found
      content:
        application/json:
          schema:
            $ref: '#/components/schemas/ErrorResponse'

    412PreconditionFailed:
      description: |-
        - Could not complete request because a constraint was not met
      content:
        application/json:
          schema:
            $ref: '#/components/schemas/ErrorResponse'

    500InternalServerError:
      description: |-
        - An unexpected error has occurred
      content:
        application/json:
          schema:
            $ref: '#/components/schemas/ErrorResponse'

  schemas:
    ErrorResponse:
      type: object
      description: |-
        - Error codes and response messages, where an error is returned
      properties:
        errorCode:
          description: |-
            - Code identifying specific error type. For more details, see “Error codes” in the API documentation
          type: string
          example: MOTH-NP-01
        errorMessage:
          description: |-
            - Additional details about the error
          maxLength: 4096
          type: string
        requestId:
          description: |-
            - ID of request. Please provide this if raising a support request.
          type: string
          example: "123-123-1234657"

    Registration:
      type: string
      description: |-
        - Registration number of the vehicle, where it was used in the request
      example: AA51AAA

    Vin:
      type: string
      description: |-
        - Vehicle Identification Number, where it was used in the request. Usually 17 alphanumeric characters.
      example: 1N4G7TCF1A9895216

    VehicleWithMotResponse:
      type: object
      description: |-
        - Vehicle data for vehicles with at least one MOT or annual test
      properties:
        registration:
          type: string
          nullable: true
          description: |-
            - Registration number of the vehicle
        make:
          type: string
          nullable: true
          example: Ford
        model:
          type: string
          nullable: true
          example: Focus
        firstUsedDate:
          type: string
          format: date
          nullable: true
          description: |-
            - Date the vehicle is first used in Great Britain, Northern Ireland or abroad
            - Format: YYYY-MM-DD
        fuelType:
          type: string
          nullable: true
          description: |-
            - The type of fuel the vehicle uses
          example: Petrol
        primaryColour:
          type: string
          nullable: true
          example: Silver
        registrationDate:
          type: string
          format: date
          nullable: true
          description: |-
            - Date the vehicle is first registered in Great Britain, Northern Ireland or abroad
            - Format: YYYY-MM-DD
        manufactureDate:
          type: string
          format: date
          nullable: true
          description: |-
            - Date the vehicle was manufactured
            - Format: YYYY-MM-DD
        engineSize:
          type: string
          nullable: true
          description: |-
            - Engine cylinder capacity (cc) of the vehicle
          example: 1598
        hasOutstandingRecall:
          type: string
          nullable: false
          enum:
            - Yes
            - No
            - Unknown
            - Unavailable
          description: |-
            - One of four values from the DVSA Recalls service:
              - Yes (There is at least one recall which has not yet been fixed)
              - No (There were one or more recalls which have all been fixed)
              - Unknown (No known recalls have been found in the available data)
              - Unavailable (We were unable to retrieve data from the Recalls service due to an error)
        motTests:
          type: array
          nullable: false
          items:
            oneOf:
              - $ref: "#/components/schemas/DVSAMotTest"
              - $ref: "#/components/schemas/DVANIMotTest"
              - $ref: "#/components/schemas/CVSMotTest"
      required:
        - hasOutstandingRecall
        - motTests

    DVSAMotTest:
      description: |-
        - Test result information from DVSA (Driver and Vehicle Standards Agency, Great Britain)
      type: object
      properties:
        completedDate:
          type: string
          format: date-time
          nullable: false
          description: |-
            - Date-time the test was completed.
            - ISO Standard Date Format
          example: "2023-02-17T09:17:46.000Z"
        testResult:
          type: string
          nullable: false
          enum:
            - PASSED
            - FAILED
          description: |-
            - Result of the MOT test. Only Passed or Failed tests are included.
          example: PASSED
        expiryDate:
          type: string
          format: date
          nullable: true
          description: |-
            - Date the MOT test will expire
            - Format: YYYY-MM-DD
        odometerValue:
          type: string
          nullable: true
          description: |-
            - Odometer reading, if read
        odometerUnit:
          type: string
          nullable: true
          enum:
            - MI
            - KM
            - null
          description: |-
            - Whether the odometer was read in miles or kilometres
          example: MI
        odometerResultType:
          type: string
          nullable: false
          enum:
            - READ
            - UNREADABLE
            - NO_ODOMETER
          description: |-
            - Whether or not the odometer was read during the MOT test. NO_ODOMETER means that a value is not available
        motTestNumber:
          type: string
          nullable: true
          description: |-
            - 12 digit MOT test number
        dataSource:
          type: string
          nullable: false
          enum:
            - DVSA
          description: |-
            - Source of the MOT test data.  In this case, DVSA (Driver and Vehicle Standards Agency, Great Britain)
        defects:
          type: array
          nullable: true
          description: |-
            - Defects found during the MOT test
          items:
            $ref: "#/components/schemas/Defect"
      required:
        - completedDate
        - testResult
        - odometerResultType
        - dataSource

    DVANIMotTest:
      type: object
      description: |-
        - Test result data from DVA NI (Driver and Vehicle Agency, Northern Ireland)
      properties:
        completedDate:
          type: string
          format: date-time
          nullable: false
          description: |-
            - Date-time the test was completed
            - ISO Standard Date Format
          example: "2023-02-17T09:17:46.000Z"
        testResult:
          type: string
          nullable: false
          enum:
            - PASSED
            - FAILED
          description: |-
            - Result of the MOT test. Only Passed or Failed tests included.
          example: PASSED
        expiryDate:
          type: string
          format: date
          nullable: true
          description: |-
            - Date the MOT test will expire
            - Format: YYYY-MM-DD
        odometerValue:
          type: string
          nullable: true
          description: |-
            - Odometer reading, if read
        odometerUnit:
          type: string
          nullable: true
          enum:
            - MI
            - KM
            - null
          description: |-
            - Whether the odometer was read in miles or kilometres
          example: KM
        odometerResultType:
          type: string
          nullable: false
          enum:
            - READ
            - NO_ODOMETER
          description: |-
            - Whether or not the odometer was read during the MOT test. Set to NO_ODOMETER if value is not available
        motTestNumber:
          nullable: true
          type: string
          description: |-
            - Identifier for the test
        dataSource:
          description: |-
            - Source of the MOT test data.  In this case, DVA NI (Driver and Vehicle Agency, Northern Ireland)
          type: string
          nullable: false
          enum:
            - DVA NI
      required:
        - completedDate
        - testResult
        - odometerResultType
        - dataSource

    CVSMotTest:
      description: |-
        - Test result information from CVS (Driver and Vehicle Standards Agency, Commercial Vehicle Service)
      type: object
      properties:
        completedDate:
          type: string
          format: date-time
          nullable: true
          description: |-
            - Date-time the test was completed
            - ISO Standard Date Format
          example: "2023-02-17T09:17:46.000Z"
        testResult:
          type: string
          nullable: false
          enum:
            - PASSED
            - FAILED
          description: |-
            - Result of the MOT test. Only Passed or Failed tests included.
          example: PASSED
        expiryDate:
          type: string
          format: date
          nullable: true
          description: |-
            - Date the MOT test will expire
            - Format: YYYY-MM-DD
        odometerValue:
          type: string
          nullable: true
          description: |-
            - Odometer reading, if read
        odometerUnit:
          type: string
          nullable: true
          enum:
            - MI
            - KM
            - null
          description: |-
            - Whether the odometer was read in miles or kilometres
          example: KM
        odometerResultType:
          type: string
          nullable: false
          enum:
            - READ
            - NO_ODOMETER
          description: |-
            - Where the odometerResultType isn't available set to NO_ODOMETER
        motTestNumber:
          type: string
          nullable: true
          description: |-
            - Test certificate number
        location:
          type: string
          nullable: true
          description: |-
            - Name of the Authorised Test Facility (ATF) where the test was conducted
        dataSource:
          type: string
          nullable: false
          enum:
            - CVS
          description: |-
            - Source of the MOT test data.  In this case, CVS (Driver and Vehicle Standards Agency, Commercial Vehicle Service)
        defects:
          description: |-
            - Details of any defects found during the test.
          type: array
          nullable: true
          items:
            $ref: "#/components/schemas/Defect"
      required:
        - completedDate
        - testResult
        - odometerResultType
        - dataSource

    Defect:
      type: object
      description: |-
        - Defects found during the MOT or annual test.
      properties:
        text:
          type: string
          nullable: true
          description: |-
            -  Description of the defect
        type:
          type: string
          enum:
            - ADVISORY
            - DANGEROUS
            - FAIL
            - MAJOR
            - MINOR
            - NON SPECIFIC
            - SYSTEM GENERATED
            - USER ENTERED
            - PRS
          nullable: true
        dangerous:
          type: boolean
          nullable: true
          description: |-
            - Whether the defect is dangerous
          example: true

    NewRegVehicleResponse:
      description: |-
        - Vehicle data for newly registered vehicles
      type: object
      properties:
        registration:
          type: string
          nullable: true
          description: |-
            - Registration number of the vehicle
        make:
          type: string
          nullable: true
          description: |-
            - Name of the vehicle manufacturer
          example: Ford
        model:
          type: string
          nullable: true
          description: |-
            - Model of the vehicle
          example: Focus
        manufactureYear:
          type: string
          nullable: true
          description: |-
            - The year the vehicle was manufactured
            - Format: YYYY
          example: 2024
        fuelType:
          type: string
          nullable: true
          description: |-
            - The type of fuel the vehicle uses
          example: Petrol
        primaryColour:
          type: string
          nullable: true
          description: |-
            - Primary paint colour of the vehicle
          example: Silver
        registrationDate:
          type: string
          format: date
          nullable: true
          description: |-
            - Date the vehicle was first registered
            - Format: YYYY-MM-DD
        manufactureDate:
          type: string
          format: date
          nullable: true
          description: |-
            - Date the vehicle was manufactured
            - Format: YYYY-MM-DD
        motTestDueDate:
          type: string
          format: date
          nullable: true
          description: |-
            - Date the first MOT test is due
            - Format: YYYY-MM-DD
        hasOutstandingRecall:
          type: string
          nullable: false
          enum:
            - Yes
            - No
            - Unknown
            - Unavailable
          description: |-
            - One of four values from the DVSA Recalls service:
              - Yes (There is at least one recall which has not yet been fixed)
              - No (There were one or more recalls which have all been fixed)
              - Unknown (No known recalls have been found in the available data)
              - Unavailable (We were unable to retrieve data from the Recalls service due to an error)
      required:
        - hasOutstandingRecall

    BulkDownloadResponse:
      description: |-
        - File information from the bulk download service
      type: object
      properties:
        bulk:
          description: |-
            - Details about the bulk file
          type: array
          nullable: false
          items:
            $ref: "#/components/schemas/FileResponse"
        delta:
          description: |-
            - Details about the delta files
          type: array
          nullable: false
          items:
            $ref: "#/components/schemas/FileResponse"

    FileResponse:
      description: |-
        - File information from the bulk download service
      type: object
      properties:
        filename:
          description: |-
            - filename of the downloaded file
          type: string
          nullable: false
        downloadUrl:
          type: string
          nullable: false
          description: |-
           - Presigned URL for the related file:
            - URL valid for 5 mins from generation
            - Expect a .gz file which contains at least one other .gz file
        fileSize:
          type: number
          nullable: false
          description: |-
           - Size of the ZIP file in bytes
        fileCreatedOn:
          type: string
          format: date
          nullable: false
          description: |-
            - Date the file was created
            - Format: YYYY-MM-DD

    RenewCredentialsRequest:
      type: object
      description: |-
        - Information required to request a new client secret.
      properties:
        awsApiKeyValue:
          type: string
          nullable: false
          description: |-
            - the api key that was issued when you registered
          example:  "your-existing-aws-api-key-value"
        email:
          type: string
          nullable: false
          description: |-
            - the email address of the primary contact of the account
          example: "user.example@email.com"

    RenewCredentialsResponse:
      type: object
      properties:
        clientSecret:
          type: string
          nullable: false
          example: 'your-new-client-secret-value'

  parameters:
    RegistrationParam:
      name: registration
      in: path
      description: |-
        - Vehicle Registration Number used as a reference for a vehicle
      required: true
      style: simple
      explode: false
      schema:
        $ref: '#/components/schemas/Registration'

    VinParam:
      name: vin
      in: path
      description: |-
        - Vehicle Identification Number used as a reference for a vehicle
      required: true
      style: simple
      explode: false
      schema:
        $ref: '#/components/schemas/Vin'

  securitySchemes:
    bearerAuth:
      type: http
      scheme: bearer
      bearerFormat: JWT
    apiKey:
      type: apiKey
      in: header
      name: X-API-Key

Kiota Version

1.16.4

Latest Kiota version known to work for scenario above?(Not required)

No response

Known Workarounds

No response

Configuration

No response

Debug output

Click to expand log

```

</details>


### Other information

_No response_

[baywet]

Hi Steve Dunn (@SteveDunn)
Thank you for using kiota and for reaching out.

Do you get an inline class generated for the motTests property array type at all in the current configuration?
If so, could you please provide it here?

Have you tried adding a discriminator on the items definition?

[SteveDunn]

Hi Vincent Biret (@baywet) - I get the following generated property:

public List<global::MotHistory.Api.Models.VehicleWithMotResponse.VehicleWithMotResponse_motTests>? MotTests { get; set; }

With a definition of:

public partial class VehicleWithMotResponse_motTests : IComposedTypeWrapper, IParsable

I'm unable to change the schema or the json as it's from a third party.

Thanks for looking into this, much appreciated.

[baywet]

Thank you for the additional information.

Does VehicleWithMotResponse_motTests have any property? (other than the standard ones that every class gets)
Can you paste the CreateFromDiscriminator static method from that class?