[Protobuf] Improve oneOf Handling by Unwrapping allOf for Complex Types

[lucy66hw]

The OpenAPI Normalizer wraps $ref with sibling properties (title, description) inside allOf constructs. The Protobuf generator wasn't properly unwrapping these single-item allOf containers, causing issues when handling complex types within oneOf.
expected:

Pet:
  oneOf:
    - allOf:  
        - $ref: '#/components/schemas/Dog'
      title: dog
      description: "A dog pet"
    - allOf:  
        - $ref: '#/components/schemas/Cat'
      title: cat
      description: "A cat pet"
    - allOf:  
        - $ref: '#/components/schemas/Bird'
      title: bird
      description: "A bird pet"

solution:
Unwrap single-item allOf: If the resolved schema is allOf with exactly one item, unwrap it.

Pet:
  oneOf:
    - title: dog  
      description: "A dog pet"
      $ref: '#/components/schemas/Dog'
    - title: cat  
      description: "A cat pet"
      $ref: '#/components/schemas/Cat'
    - title: bird  
      description: "A bird pet"
      $ref: '#/components/schemas/Bird'

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[cubic-dev-ai]

1 issue found across 3 files

Prompt for AI agents (all issues)

Check if these issues are valid — if so, understand the root cause of each and fix them.


<file name="modules/openapi-generator/src/test/java/org/openapitools/codegen/protobuf/ProtobufSchemaCodegenTest.java">

<violation number="1" location="modules/openapi-generator/src/test/java/org/openapitools/codegen/protobuf/ProtobufSchemaCodegenTest.java:192">
P2: Test does not fail for unexpected var names; missing else/set-membership assertion allows false positives.</violation>
</file>

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[cubic-dev-ai]

No issues found across 3 files

[wing328]

circleci failure not related to this change

[wing328]

thanks for the PR

let's give it a try

in the next release (v7.20.0) i may add an option to opt out of the allOf normalization to handle $ref with sibling properties in 3.1 spec as not all generators can handle such case at the moment