read-only-write-only-model-type breaks with refs

[Yamakaky]

Describe the bug
read-only-write-only-model-type doesn't support refs to others schemas with readOnly properties. In the example below, I assume the generator creates ChildResponse and ChildRequest, then search for Child when generating Parent. Same behavior if Parent also has a readOnly property.

To Reproduce

Example schema:

openapi: "3.0.0"
info:
  title: broken readonly $ref
  version: "1.0"
paths: {}
components:
  schemas:
    Child:
      properties:
        opt:
          readOnly: true
          type: integer
    Parent:
      properties:
        child:
          $ref: "#/components/schemas/Child"
        opt:
          readOnly: true
          type: integer

Used commandline:

$ datamodel-codegen --input example.yaml --read-only-write-only-model-type request-response

Expected behavior
If $ref points to a schema with readonly fields, the parent schema should always be a request/response, and use the right ref.

Version:

• OS: linux
• Python version: 3.14
• datamodel-code-generator version: 0.55.2

[Yamakaky]

That's a quick fix !

[github-actions]

🎉 Released in 0.53.0

The fix/feature from PR #2942 has been included in this release. See the release notes for details.

Thank you for your contribution!

[Yamakaky]

Hum, I don't think the generation is correct. The initial snippet generates as the following. Arguably, this should be ChildRequest instead of Child.

class Child(BaseModel):                                                                                                                                                                   
    opt: int | None = None                                                                                                                                                                
                                                                                                                                                                                          
                                                                                                                                                                                          
class ParentRequest(BaseModel):                                                                                                                                                           
    child: Child | None = None

Adding a opt2: type: int Child property removes the read_only property:

class ChildRequest(BaseModel):                                                                                                                                                            
    opt2: int | None = None

And if I remove the Parent read_only property (I assume that would be allowed by the spec?), I get the initial error A Parser can not resolve classes: [class: #/components/schemas/Parent references: frozenset({'#/components/schemas/Child'})]

openapi: "3.0.0"
info:
  title: broken readonly $ref
  version: "1.0"
paths: {}
components:
  schemas:
    Child:
      properties:
        opt:
          readOnly: true
          type: integer
    Parent:
      properties:
        child:
          $ref: "#/components/schemas/Child"

[Yamakaky]

BTW, what should happen if there are no non-read-only fields? We don't generate an empty ChildResponse? The openapi spec doesn't seem to be explicit on that, I can only see definitions for member fields, not sub-member.

Also what should happen if a component with only readonly in sub properties if used as a query body? Should it accept an empty body or no body at all? My 2 cents is that it should be a validation error at the openapi spec level, or at least a warning