fix: do not mint a duplicate model for a single-$ref allOf property

[rmocanu-ionos]

InlineModelResolver.isModelNeeded() treated a property written as

properties:
  bootVolume:
    allOf:
      - $ref: '#/components/schemas/ResourceReference' description: ...

as needing its own inline model, so the resolver minted a duplicate schema (ServerPropertiesBootVolume) instead of reusing the referenced one. The sibling keyword is the trigger: a bare $ref cannot carry a description, so spec authors wrap it in a single-element allOf, which is the idiomatic OpenAPI 3.0 workaround and means "this property IS the referenced schema".

The existing loop below dereferences each allOf member via getReferencedSchema() and reports "model needed" for any object target, which is correct for a real composition but wrong for the alias case. Handle the single-$ref case before that loop and recurse on the RAW ref schema, so the property resolves to the referenced model.

Effect on the IONOS cloudapi-v6 spec, measured A/B against an otherwise identical run: ServerProperties.bootCdrom and bootVolume resolve to ResourceReference and maintenanceWindow to ServerMaintenanceWindow, matching what sdk-go has shipped since v6.3.11. 21 exported symbols removed, 0 added, 3 dead files gone; purely subtractive. Verified for go (build + vet), java (mvn compile), node (tsc --noEmit) and python.

Note this is subtractive by construction: it removes generated types that were duplicates. Before pointing an already-released product at this build, check that none of the types it drops are types that product has shipped.

Uses a plain null/isEmpty check rather than StringUtils.isNotEmpty, which the codegen StringUtils imported by this file does not provide.

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[Copilot]

Pull request overview

Prevents duplicate inline models for properties represented by a single-reference allOf.

Changes:

• Detects single-$ref allOf aliases.
• Reuses the referenced schema instead of minting a duplicate model.

Suppressed comments (1)

modules/openapi-generator/src/main/java/org/openapitools/codegen/InlineModelResolver.java:244

• This model-resolution regression is not covered by an automated test, although InlineModelResolverTest extensively tests flatten. Add a property with a description plus a single-$ref allOf and assert that flattening reuses the referenced schema without creating <Parent>_<property>; include a combined-composition case so the alias shortcut remains narrowly scoped.

                return isModelNeeded(m.getAllOf().get(0), visitedSchemas);

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[rmocanu-ionos]

Added the regression test (testSingleRefAllOfPropertyReusesReferencedSchema + fixture) — it fails on the parent commit and passes with the fix, 45 tests green.

Skipping the guard: allOf combined with anyOf/oneOf/not occurs nowhere in public/cloud/v6.ga.yaml, public-preview/cloud/v7.ea.yml, or any fixture with a $ref allOf member, so the path is unreachable for this fork. Two notes on the reasoning though — isModelNeeded has no not check at all, and the pre-existing allOf loop already returned before the anyOf/oneOf checks, so the ordering isn't the mechanism, the changed return value is.