What

getDiscriminatorPropertyType resolved the discriminator property's type only from the oneOf/anyOf schema's own properties, defaulting to "string" otherwise. For a pure oneOf/anyOf interface whose discriminator property lives on a shared base the children inherit via allOf, this produced a String getter that clashed with the enum the subtypes actually expose.

This adds a fallback (in DiscriminatorUtils) that resolves the type from the mapped child schemas, chasing the property through each child's allOf members. It only fires when the previous code would have returned "string", so existing specs are unaffected — regenerating the full sample suite produces no diffs.

Scenarios covered

Simples example where the discriminator is in the base object that is separate from the schema that contains oneOf

PetRequest:
      type: object
      oneOf:
        - $ref: '#/components/schemas/CatRequest'
        - $ref: '#/components/schemas/DogRequest'
      discriminator:
        propertyName: petType
        mapping:
          CAT: '#/components/schemas/CatRequest'
          DOG: '#/components/schemas/DogRequest'

    # Shared base WITHOUT a discriminator, so children flatten it via allOf
    # instead of extending it (which would create a cyclical reference).
    PetBase:
      type: object
      required:
        - petType
        - name
      properties:
        petType:
          $ref: '#/components/schemas/PetType'  # ---> This would be duplicated into PetRequest without this PR refactor
        name:
          type: string

    CatRequest:
      type: object
      allOf:
        - $ref: '#/components/schemas/PetBase'
        - type: object
          required:
            - indoor
          properties:
            indoor:
              type: boolean

    DogRequest:
      type: object
      allOf:
        - $ref: '#/components/schemas/PetBase'
        - type: object
          required:
            - trained
          properties:
            trained:
              type: boolean

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Summary by cubic

Fixes discriminator type resolution for oneOf/anyOf interfaces by deriving the property type from child schemas (via allOf) with cycle-safe recursion. Getter types now use the correct enum (e.g., PetType) instead of "string", avoiding interface vs subtype mismatches.

• Bug Fixes
  • Updated DiscriminatorUtils.getDiscriminatorPropertyType(OpenAPI, ...) to first check the schema’s own $ref, then fall back to oneOf/anyOf children via getDiscriminatorPropertyTypeFromChildren and recursive getDiscriminatorSchemaDeep (supports multi-level allOf with a visited guard for cycles).
  • Updated DefaultCodegen.getDiscriminatorPropertyType to pass openAPI, map to model names, and keep the "string" fallback.
  • Added DiscriminatorUtilsTest, expanded DefaultCodegenTest, and new YAMLs (oneOf/anyOf, nested base, cyclic, string fallback). Regenerating samples shows no diffs.

^{Written for commit a0934fe. Summary will update on new commits.}