Update normalizer to clear types when $ref is set

[wing328]

Updated normalizer to clear types when $ref is set (show a warning saying so)
Added a test in java client.

to close #22919

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---

Summary by cubic

Normalize reference schemas to clear type/types when $ref is set, preventing conflicting definitions and aligning with OpenAPI 3.1 behavior. Updated the Java 3.1 Petstore sample and tests to cover object|null + $ref cases.

• Bug Fixes
  • Clear type/types when a schema has $ref and log a warning.
  • Added PetWithTypesObjectNullAndRef to the 3.1 Petstore sample; generated code now treats the property as a Pet via $ref.
  • Updated Java client model, docs, and test to validate the behavior.

^{Written for commit 5468ae8. Summary will update on new commits.}

[cubic-dev-ai]

1 issue found across 9 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="samples/client/petstore/java/okhttp-gson-3.1/src/main/java/org/openapitools/client/model/PetWithTypesObjectNullAndRef.java">

<violation number="1" location="samples/client/petstore/java/okhttp-gson-3.1/src/main/java/org/openapitools/client/model/PetWithTypesObjectNullAndRef.java:189">
P2: Guard against null before calling getAsJsonObject(); otherwise valid null JSON triggers a NullPointerException when no required fields are present.</violation>
</file>

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

[cubic-dev-ai]

P2: Guard against null before calling getAsJsonObject(); otherwise valid null JSON triggers a NullPointerException when no required fields are present.

Prompt for AI agents

Check if this issue is valid — if so, understand the root cause and fix it. At samples/client/petstore/java/okhttp-gson-3.1/src/main/java/org/openapitools/client/model/PetWithTypesObjectNullAndRef.java, line 189:

<comment>Guard against null before calling getAsJsonObject(); otherwise valid null JSON triggers a NullPointerException when no required fields are present.</comment>

<file context>
@@ -0,0 +1,288 @@
+          throw new IllegalArgumentException(String.format(java.util.Locale.ROOT, "The required field(s) %s in PetWithTypesObjectNullAndRef is not found in the empty JSON string", PetWithTypesObjectNullAndRef.openapiRequiredFields.toString()));
+        }
+      }
+        JsonObject jsonObj = jsonElement.getAsJsonObject();
+      // validate the optional field `first_property`
+      if (jsonObj.get("first_property") != null && !jsonObj.get("first_property").isJsonNull()) {
</file context>

[wing328]

not related to this PR

we can file another PR in the future to have better guard against NPE in this code block

[cubic-dev-ai]

Thanks for clarifying—understood this is out of scope for this PR.