Model Composition with ‘allOf’ Is Missing Fields

Describe the bug
Using a composition model (https://spec.openapis.org/oas/v3.0.4.html#models-with-composition) does not generate the target type but only the underlying type. For a type A which consists of the fields of B and some additional fields, only B is generated. Furthermore, A is replaced by B.

The spec below generates the following function:

def sync_detailed(
    *,
    client: AuthenticatedClient | Client,
    body: Base,
) -> Response[Any]: ...

I would expect that the model Network is generated and used instead of Base. The Network model should include the field of Base and the field non_base_field.

OpenAPI Spec File

openapi: 3.0.0
info:
  title: Service
  version: 0.0.0
paths:
  /widgets:
    get:
      responses:
        "200":
          description: The request has succeeded.
          content:
            application/json:
              schema:
                nullable: true
      requestBody:
        required: true
        content:
          application/json:
            schema:
              $ref: "#/components/schemas/Network"
components:
  schemas:
    Base:
      type: object
      required:
        - base_field
      properties:
        base_field:
          type: string
    Network:
      type: object
      required:
        - non_base_field
      properties:
        non_base_field:
          type: string
      allOf:
        - $ref: "#/components/schemas/Base"

Desktop (please complete the following information):

• OS: Linux
• Python Version: 3.13.11
• openapi-python-client version: 0.28.1

Additional context
Add any other context about the problem here.

Commencez par exécuter la spécification OpenAPI fournie et comparez les modèles Network et Base générés ainsi que la signature de sync_detailed. Suivez la manière dont les schémas allOf sont traités lors de la génération des modèles et des endpoints. Le travail est terminé lorsque Network est généré avec les deux champs, que l’endpoint utilise Network au lieu de Base et qu’un test de régression couvre cette composition.