fix: serialize undefined array elements as null by treehill05 · Pull Request #1505 · middleapi/orpc

treehill05 · 2026-03-25T22:31:28Z

Fixes #1504

Summary by CodeRabbit

Bug Fixes
- Fixed JSON serialization handling of undefined values in arrays to ensure proper round-trip serialization and deserialization.
Tests
- Added comprehensive test coverage for undefined array element handling, including nested cases.

coderabbitai · 2026-03-25T22:31:42Z

No actionable comments were generated in the recent review. 🎉

ℹ️ Recent review info

⚙️ Run configuration

Configuration used: defaults

Review profile: CHILL

Plan: Pro

Run ID: ae303943-096e-4683-8226-efd3309af565

📥 Commits

Reviewing files that changed from the base of the PR and between 8d90c8f and 3d25f32.

📒 Files selected for processing (2)

packages/client/src/adapters/standard/rpc-json-serializer.test.ts
packages/client/src/adapters/standard/rpc-json-serializer.ts

📝 Walkthrough

Walkthrough

Fixed a JSON serialization bug where undefined array elements were output as undefined instead of null, breaking SSR hydration. The serializer now outputs null placeholders with metadata for reconstruction during deserialization, ensuring JSON compatibility through all transport layers.

Changes

Cohort / File(s)	Summary
Serializer Implementation `packages/client/src/adapters/standard/rpc-json-serializer.ts`	Changed array element serialization to return `null` instead of `undefined` for `undefined` values, allowing safe passage through JSON serialization boundaries while metadata preserves the original value for deserialization.
Test Coverage `packages/client/src/adapters/standard/rpc-json-serializer.test.ts`	Added test suite validating `undefined` array element handling, including round-trip serialization/deserialization and nested array scenarios (e.g., TanStack Query `pageParams`).

Estimated code review effort

🎯 2 (Simple) | ⏱️ ~10 minutes

Possibly related PRs

fix(client, server): prevent toJSON problem #279: Modifies the same StandardRPCJsonSerializer.serialize() method, introducing additional changes to serialization behavior.

Suggested labels

size:S

Poem

🐰 A hop and a fix for arrays so grand,
Where undefined now safely lands—
As null it hides with metadata's care,
JSON highways pass without despair!

🚥 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 core change: undefined array elements are now serialized as null instead of undefined.
Linked Issues check	✅ Passed	The code changes fully address the linked issue `#1504` by fixing serialization of undefined array elements to use null placeholders while maintaining meta entries for deserialization recovery.
Out of Scope Changes check	✅ Passed	All changes are directly scoped to fixing the undefined array serialization issue; no unrelated modifications are present.
Docstring Coverage	✅ Passed	No functions found in the changed files to evaluate docstring coverage. Skipping docstring coverage check.

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gemini-code-assist · 2026-03-25T22:31:44Z

Summary of Changes

Hello, I'm Gemini Code Assist¹! I'm currently reviewing this pull request and will post my feedback shortly. In the meantime, here's a summary to help you and other reviewers quickly get up to speed!

This pull request addresses an issue where undefined elements within arrays were not properly handled during JSON serialization, potentially leading to non-standard JSON output. The changes ensure that such elements are serialized as null for compatibility, while maintaining the original undefined state upon deserialization, thereby improving the robustness and correctness of the RPC JSON serializer.

Highlights

Undefined Array Element Serialization: Modified the StandardRPCJsonSerializer to serialize undefined elements within arrays as null to ensure JSON-safe output. Deserialization correctly restores these null values back to undefined.

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Code Review

This pull request updates the StandardRPCJsonSerializer to correctly handle undefined values within arrays by serializing them as null for JSON compatibility and using metadata to restore them to undefined upon deserialization. New tests have been added to verify this behavior for both simple and nested arrays. The reviewer suggests adding an additional test case to cover undefined values as object properties, as the current tests focus solely on arrays.

packages/client/src/adapters/standard/rpc-json-serializer.test.ts

codecov · 2026-03-26T01:56:15Z

Codecov Report

✅ All modified and coverable lines are covered by tests.

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pkg-pr-new · 2026-03-26T01:56:38Z

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commit: b216502

fix: serialize undefined array elements as null

3d25f32

dosubot bot added the size:S This PR changes 10-29 lines, ignoring generated files. label Mar 25, 2026

dosubot bot added bug Something isn't working javascript Pull requests that update javascript code labels Mar 25, 2026

gemini-code-assist bot reviewed Mar 25, 2026

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packages/client/src/adapters/standard/rpc-json-serializer.test.ts Show resolved Hide resolved

dinwwwh approved these changes Mar 26, 2026

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dosubot bot added the lgtm This PR has been approved by a maintainer label Mar 26, 2026

dinwwwh merged commit 89acf15 into middleapi:main Mar 26, 2026
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fix: serialize undefined array elements as null#1505

fix: serialize undefined array elements as null#1505
dinwwwh merged 1 commit intomiddleapi:mainfrom
treehill05:fix/serialize-undefined-array-elements-as-null

treehill05 commented Mar 25, 2026 •

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