Fix FastAPI example generation

[Goopher]

Fixes FastAPI server example generation so explicit OpenAPI examples are included in generated FastAPI/Pydantic metadata.

Changes:

• Adds explicit request body examples to generated FastAPI Body(..., examples=[...]) metadata.
• Preserves schema/property examples in generated Pydantic fields using json_schema_extra={"examples": [...]}.
• Avoids leaking generated fallback examples like '', None, or empty array placeholders into Swagger UI.
• Uses plural examples for FastAPI metadata to avoid example deprecation warnings.
• Adds FastAPI generator tests covering request body examples and schema property examples.

Validation:

mvn -pl modules/openapi-generator -Dtest=PythonFastAPIServerCodegenTest -Dsurefire.failIfNoSpecifiedTests=true test

Result:

Tests run: 3, Failures: 0, Errors: 0, Skipped: 0

### PR checklist

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  Commit all changed files.
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<!-- This is an auto-generated description by cubic. -->
---
## Summary by cubic
Fixes FastAPI example generation so explicit OpenAPI examples — including plural `examples` and `$ref` examples — render in generated endpoints, parameters, and models without placeholders. Also keeps trailing commas inline on generated endpoint parameters.

- **Bug Fixes**
- Request body examples: `Body(..., examples=[...])` from `application/json`, resolving requestBody and `$ref`-ed `components/examples`.
- Non-body params: `examples=[...]` with safe Python literals; avoids placeholder fallbacks in Swagger UI.
- Models/fields: `json_schema_extra={"examples": [...]}` using `example`, else first from `examples` (covers OAS 3.1).
- Formatting: keep trailing comma on the same line in generated endpoint parameters.
- Tests for body examples, schema property examples, and singular vs plural example precedence.

<sup>Written for commit 949744ad250980d3a59d3078ec9b3a78c6f6f9d6. Summary will update on new commits.</sup>

<!-- End of auto-generated description by cubic. -->

[cubic-dev-ai]

1 issue found across 5 files

Prompt for AI agents (unresolved issues)

Check if these issues are valid — if so, understand the root cause of each and fix them. If appropriate, use sub-agents to investigate and fix each issue separately.


<file name="modules/openapi-generator/src/main/java/org/openapitools/codegen/languages/AbstractPythonCodegen.java">

<violation number="1" location="modules/openapi-generator/src/main/java/org/openapitools/codegen/languages/AbstractPythonCodegen.java:686">
P2: Schema example extraction only checks `example` and ignores `examples`, which can drop explicit schema examples in generated Python metadata.</violation>
</file>

_{Reply with feedback, questions, or to request a fix. Tag @cubic-dev-ai to re-run a review.}

[wing328]

Thanks for the PR but your commit (as shown in the Commits tab) is not linked to your Github account, which means this PR won't count as your contribution in https://github.com/OpenAPITools/openapi-generator/graphs/contributors.

Let me know if you need help fixing it.

Ref: https://github.com/OpenAPITools/openapi-generator/wiki/FAQ#how-can-i-update-commits-that-are-not-linked-to-my-github-account

[Goopher]

Thanks for the PR but your commit (as shown in the Commits tab) is not linked to your Github account, which means this PR won't count as your contribution in https://github.com/OpenAPITools/openapi-generator/graphs/contributors.

Let me know if you need help fixing it.

Ref: https://github.com/OpenAPITools/openapi-generator/wiki/FAQ#how-can-i-update-commits-that-are-not-linked-to-my-github-account

Thanks for notifying me, fixed.

[wing328]

--- a/samples/server/petstore/python-fastapi/src/openapi_server/apis/pet_api.py
+++ b/samples/server/petstore/python-fastapi/src/openapi_server/apis/pet_api.py
@@ -50,7 +50,8 @@ for _, name, _ in pkgutil.iter_modules(ns_pkg.__path__, ns_pkg.__name__ + "."):
     response_model_by_alias=True,
 )
 async def update_pet(
-    pet: Annotated[Pet, Field(description="Pet object that needs to be added to the store")] = Body(None, description="Pet object that needs to be added to the store"),
+    pet: Annotated[Pet, Field(description="Pet object that needs to be added to the store")] = Body(None, description="Pet object that needs to be added to the store")
+,
     token_petstore_auth: TokenModel = Security(
         get_token_petstore_auth, scopes=["write:pets", "read:pets"]
     ),

can we keep the , (comma) in the same line instead of a new line?

ref: https://github.com/OpenAPITools/openapi-generator/actions/runs/24402803325/job/71278593153?pr=23537 (please update the samples by following step 3 in the PR checklist)