test(lotus_json): assert LotusJson<Option<T>> is nullable in schema

[0xDevNinja]

Summary

Closes#4331.

LotusJson<Option<T>> delegates its schema to Option<T::LotusJson>, which schemars already renders as nullable ("type": [..., "null"] / a null branch in anyOf). This adds a small regression test locking that behaviour in, as suggested in the issue — verifying that:

• LotusJson<Option<T>> produces a schema that permits null (i.e. is optional in the OpenRPC spec), and
• the non-optional LotusJson<T> counterpart does not permit null.

The helper schema_allows_null accepts both the "type" union form (used for primitives/arrays) and the anyOf/oneOf form (used for $ref object types), so the test stays robust across inner types.

No production code changes — test only.

Reference tests

cargo test -p forest-filecoin --lib lotus_json::opt:: — 3 passed (existing snapshot + quickcheck, plus the new optional_is_nullable_in_schema).

Other information and links

Issue originally raised by @ruseinov in #4330 (comment).

Summary by CodeRabbit

• Tests
  • Added regression coverage to ensure optional Lotus JSON values accept null in generated JSON/OpenRPC schemas.
  • Verified non-optional Lotus JSON values do not permit null in the corresponding schemas.

[coderabbitai]

No actionable comments were generated in the recent review. 🎉

ℹ️ Recent review info

⚙️ Run configuration

Configuration used: Repository UI

Review profile: CHILL

Plan: Pro

Run ID: ec5a7a19-98fb-40e9-8d8e-21186f79a8c8

📥 Commits

Reviewing files that changed from the base of the PR and between 375530d and afd870c.

📒 Files selected for processing (1)

• src/lotus_json/opt.rs

🔗 Linked repositories identified

CodeRabbit considers these linked repositories for cross-repo context during reviews:

• filecoin-project/lotus(manual)

🚧 Files skipped from review as they are similar to previous changes (1)

• src/lotus_json/opt.rs

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Walkthrough

Changes

LotusJson schema nullability

Layer / File(s)	Summary
Schema nullability regression coverage src/lotus_json/opt.rs	Adds schema_allows_null and verifies that LotusJson<Option<Cid>> accepts null, while LotusJson<Cid> does not.

Estimated code review effort: 2 (Simple) | ~10 minutes

Suggested reviewers:hanabi1224

🚥 Pre-merge checks | ✅ 5

✅ Passed checks (5 passed)

Check name	Status	Explanation
Description Check	✅ Passed	Check skipped - CodeRabbit’s high-level summary is enabled.
Title check	✅ Passed	The title accurately describes the added regression test for LotusJson<Option> schema nullability.
Linked Issues check	✅ Passed	The new test verifies that LotusJson<Option> is nullable in schema while LotusJson is not, matching issue #4331.
Out of Scope Changes check	✅ Passed	The PR only adds a focused regression test and helper, with no unrelated code changes.
Docstring Coverage	✅ Passed	Docstring coverage is 100.00% which is sufficient. The required threshold is 80.00%.

✨ Finishing Touches

🧪 Generate unit tests (beta)

• Create PR with unit tests

✨ Simplify code

• Create PR with simplified code

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[hanabi1224]

LGTM, thanks! There is an outstanding lint issue to fix tho.

[codecov]

Codecov Report

❌ Patch coverage is 94.73684% with 1 line in your changes missing coverage. Please review.
✅ Project coverage is 65.05%. Comparing base (17c49db) to head (afd870c).
⚠️ Report is 36 commits behind head on main.
✅ All tests successful. No failed tests found.

Files with missing lines	Patch %	Lines
src/lotus_json/opt.rs	94.73%	1 Missing ⚠️

Additional details and impacted files

Files with missing lines	Coverage Δ
src/lotus_json/opt.rs	91.17% <94.73%> (+4.50%)	⬆️

... and 66 files with indirect coverage changes

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[sudo-shashank]

lint:spellcheck failing

[0xDevNinja]

Good catch, thanks. Fixed the spellcheck failure by rewording the doc comment to avoid the word that tripped the dictionary. Should be green now.

[sudo-shashank]

@0xDevNinjalint:clippy check is failing

[0xDevNinja]

Thanks, fixed. The collapsible_match lint was on my helper in opt.rs, so I reworked it to compute the result without the nested if. Verified locally with clippy on the lib and test targets plus the unit tests, all green now.

[sudo-shashank]

LGTM