I have the following OpenAPI spec which does not appear to work in terms of generating an Optional field:

components:
    Foo:
          type: object
          nullable: true
          properties:
              bar:
              type: string
    Thing:
      type: object
      properties:
        foo:
            $ref: '#/components/schemas/Foo'

This is using flags:

--use-title-as-name \
--input-file-type openapi \
--snake-case-field \
--base-class lib.CamelCaseBaseModel \
--target-python-version 3.9 \
--validation \
--strict-nullable

I have the following OpenAPI spec which does work in terms of generating an Optional field:

    Thing:
      type: object
      properties:
        foo:
          type: object
          nullable: true
          properties:
              bar:
              type: string

The correct output I'm after is:

foo: Optional[Foo] = Field(...)

What I'm actually doing is bundling via redoc with:

redocly bundle openapi/openapi.yaml --output openapi-generated.yaml
python -m datamodel_code_generator \
--input openapi-generated.yaml \
--output lib/models.py \
--use-title-as-name \
--input-file-type openapi \
--snake-case-field \
--base-class lib.CamelCaseBaseModel \
--target-python-version 3.9 \
--validation \
--strict-nullable

I can work around (or will just use) --dereference for redocly but thought I'd flag what I think is a bug.

Version:

• Python version: 3.9
• datamodel-code-generator version: v0.19.0