Java: Generate typed catalogue candidates

[gokhanarkan]

Summary

• generate typed Java catalogue candidates instead of List<Object>
• keep non-catalogue and non-Java generated output unchanged

Validation

• npm --prefix java/scripts/codegen test
• repeated Java codegen with zero non-Catalog generated delta
• cd java && mvn verify

Related to #2106

[Copilot]

Copilot review overview

🟡 Changes recommended

Generated polymorphic candidates can serialize duplicate discriminator properties.

Once you've addressed the issues Copilot identified, you can request another Copilot review.

Review tier: Balanced
Findings: 1

New issues introduced by this change (1)

Severity	Finding
	java/​scripts/​codegen/​java.ts — Returning the promoted union as a polymorphic type also changes serialization:…

What changed in this PR

Generates typed Java catalogue candidate hierarchies from nested discriminated unions.

Changes:

• Promotes nested catalogue unions into generated Java types.
• Adds candidate/source classes and typed candidate lists.
• Adds generator and Jackson coverage.

File	Description
CatalogCandidateJacksonTest.java	Tests candidate deserialization and round-tripping.
CatalogSearchSucceeded.java	Uses typed candidates.
CatalogMcpServerInstallability.java	Adds installability enum.
CatalogMcpServerCandidateProvenance.java	Adds MCP provenance type.
CatalogMcpServerCandidate.java	Adds MCP candidate variant.
CatalogCandidateSourceUrl.java	Adds URL source variant.
CatalogCandidateSourceEmbedded.java	Adds embedded source variant.
CatalogCandidateSource.java	Adds source union base.
CatalogCandidate.java	Adds candidate union base.
CatalogAiSkillCandidateProvenance.java	Adds skill provenance type.
CatalogAiSkillCandidate.java	Adds AI skill candidate variant.
java/​scripts/​codegen/​package.json	Adds generator test command.
java/​scripts/​codegen/​java.ts	Implements nested-union promotion.
java/​scripts/​codegen/​java.test.ts	Tests promoted type resolution.

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[gokhanarkan]

@SteveSandersonMS CI is green. This is the agreed Java-only scope: typed catalogue candidate and source generation, with non-Catalogue and non-Java output unchanged. Would you mind taking a look?

[SteveSandersonMS]

I verified this is a minimal Java-only codegen parity fix: other SDK RPC output is unchanged, non-catalog Java output regenerates byte-identically, and the catalog unions now deserialize and serialize with the existing discriminators exactly once. I also resolved the package.json conflict against main while retaining both schema-fetch and codegen tests.

[github-actions]

Cross-SDK Consistency Review — PR #2532

Scope: Java-only change (codegen script + generated types), fixing CatalogSearchSucceeded.candidates which was previously untyped (List<Object>) in Java while all other SDKs already used the properly-typed candidate union:

• TypeScript: candidates: CatalogCandidate[]
• Python: candidates: list[CatalogCandidate]
• Go: Candidates []CatalogCandidate
• Rust: pub candidates: Vec<CatalogCandidate>
• .NET: uses the analogous typed generated model

The root cause was the Java codegen's handling of nested discriminated unions inside array items — it wasn't promoting CatalogCandidate (and its Catalog*Candidate/Catalog*Provenance/Catalog*Source* variants) to named types. This PR adds collectNestedDiscriminatedUnionTypeNames to java/scripts/codegen/java.ts, regenerates the new Java model classes, and adds targeted unit/Jackson serialization tests.

Assessment: ✅ No consistency issue — this brings Java into parity with the other five SDKs rather than creating a gap. It's a bugfix confined to the Java codegen pipeline and generated output; no behavior or API changed in TS/Python/Go/.NET/Rust, so no cross-language follow-up is needed.

Generated by SDK Consistency Review Agent for #2532 · copilot · sonnet50 · 28.6 AIC · ⌖ 11.9 AIC · ⊞ 9.7K · ◷