Inline oneOf variants with properties/required fail: "Invalid property in union"

Description

When a schema uses oneOf with inline object variants (each having properties and required but no $ref), the generator fails with:

Invalid property in union <property_name>

This happens regardless of whether anyOf or oneOf is used. The issue is that the generator cannot process inline discriminated union variants that define their own properties — it expects $ref pointers to named component schemas.

Minimal Reproduction

openapi: "3.0.3"
info:
  title: Test
  version: "1.0"
paths: {}
components:
  schemas:
    MyModel:
      type: object
      properties:
        rules:
          type: array
          items:
            type: object
            oneOf:
              - properties:
                  rule_type:
                    type: string
                    enum: ["type_a"]
                  value_a:
                    type: string
                required: ["rule_type", "value_a"]
              - properties:
                  rule_type:
                    type: string
                    enum: ["type_b"]
                  value_b:
                    type: integer
                required: ["rule_type", "value_b"]

$ openapi-python-client generate --path spec.yaml
Unable to process schema /components/schemas/MyModel:
Invalid property in union rules_item

Workaround

Extracting each variant into a named component schema and using $ref works:

components:
  schemas:
    RuleTypeA:
      type: object
      properties:
        rule_type:
          type: string
          enum: ["type_a"]
        value_a:
          type: string
      required: ["rule_type", "value_a"]
    RuleTypeB:
      type: object
      properties:
        rule_type:
          type: string
          enum: ["type_b"]
        value_b:
          type: integer
      required: ["rule_type", "value_b"]
    MyModel:
      type: object
      properties:
        rules:
          type: array
          items:
            oneOf:
              - $ref: "#/components/schemas/RuleTypeA"
              - $ref: "#/components/schemas/RuleTypeB"

Related

• #868 — similar "Invalid property in union" error with anyOf/allOf combinations
• Both inline oneOf and anyOf variants trigger the same failure

Version

• openapi-python-client: 0.28.2

まず最小限の再現ケースで openapi-python-client generate --path spec.yaml を実行し、Invalid property in union を報告するスキーマユニオンの処理を追跡してください。Issue にはソースファイルやテストパスが記載されていないため、最初に $ref ベースの oneOf/anyOf バリアントを既存のどのように処理しているかを見つけてください。properties と required を持つインラインバリアントが正常に生成され、文書化された $ref の回避策も引き続き機能すれば完了です。