fix: core: preserve OAS 3.1 numeric exclusive validation constraints in composed schemas

[raichuchuchu]

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PR Description Summary

• Problem: OAS 3.1 numeric exclusive constraints were lost during code generation, especially when using allOf or model composition.
• Solution: Synchronized OAS 3.1 numeric validation logic into ModelUtils#syncValidationProperties to ensure constraints are correctly mapped to CodegenProperty even in flattened or composed models.
• Tests: Added comprehensive test cases in ExclusiveMinMaxTest.java covering OAS 3.0/3.1 syntax, "stricter-wins" logic, and allOf inheritance.

Description

This PR fixes a regression where OpenAPI 3.1 numeric exclusiveMinimum and exclusiveMaximum constraints were lost during code generation, particularly when using model composition (allOf) with $ref.

About Core Logic

Previously, in #22981, handling for OAS 3.1 numeric exclusive constraints was introduced in OpenAPINormalizer.java. However, due to the way OpenAPINormalizer runs early in the pipeline and how it handles recursive schema resolution, constraints were often lost when a model was defined using allOf combined with $ref. The normalization would skip referenced schemas or fail to persist the flags through the flattening process.

This PR synchronizes the "stricter-wins" validation logic into ModelUtils#syncValidationProperties. By handling the conversion from 3.1 numeric values to 3.0 boolean flags at this later stage (during CodegenProperty population), we ensure that:

1. Validations are correctly preserved even in complex composed/flattened models.
2. The logic remains robust regardless of whether the OpenAPI Normalizer is enabled.
3. Legacy OAS 3.0 boolean constraints continue to work as expected.

Notably, this implementation serves as a reliable fail-safe. Even if the normalization logic in OpenAPINormalizer (introduced in #22981) were to be disabled or reverted, the new ExclusiveMinMaxTest.java will still pass. While a revert might cause the specific internal tests in OpenAPINormalizerTest to fail, the focus of this PR is ensuring the behavioral correctness of the final code generation output.

About Test Case

The tests introduced in #22981 (OpenAPINormalizerTest.java) verified the state of the intermediate Schema objects but did not validate the final CodegenProperty output, which is what templates actually use.

I have added ExclusiveMinMaxTest.java, which rewrites and expands these tests to:

• Verify the final constraints on CodegenProperty.
• Cover edge cases such as "inclusive boundary being stricter than exclusive boundary."
• Ensure allOf inheritance correctly propagates exclusive constraints from parent schemas to child properties.

Validation

Verified the fix using:

./mvnw -pl modules/openapi-generator test -Dtest=ExclusiveMinMaxTest

All tests passed, confirming that constraints are now correctly mapped to the generated model properties.

Ran ./bin/generate-samples.sh . No changes observed in existing samples, indicating no regressions for legacy OAS 2.0/3.0 specifications.

---

Summary by cubic

Fixes preservation of OAS 3.1 numeric exclusiveMinimum/exclusiveMaximum in generated models and composed schemas, and keeps OAS 3.0 behavior intact.

• Bug Fixes
  • Handle exclusiveMinimumValue/exclusiveMaximumValue (OAS 3.1) in ModelUtils: hasValidation, hasCommonAttributesDefined, and syncValidationProperties.
  • Stricter-wins merge: numeric exclusive values replace min/max when equal or stricter; inclusive stricter bounds remain.
  • Preserve OAS 3.0 boolean exclusive flags as-is.
  • Add tests for 3.1 endpoints and composed models, and new 3.0 spec to verify allOf inheritance and backward compatibility (PriceDto2/3).

^{Written for commit 2469074. Summary will update on new commits.}

[cubic-dev-ai]

No issues found across 5 files

[wing328]

lgtm. thanks for the contribution