fix: isJSONSerializable returns true for null (#571)

[rafaumeu]

Fixes #571

Bug Description:

The function had a critical bug on line 22 where it checked t === null,
but typeof never returns "null" (typeof null === "object").

This caused three issues:

1. Dead code: t === null was always false
2. isJSONSerializable(null) threw TypeError: "Cannot read properties of null (reading buffer)"
3. null was incorrectly identified as not JSON serializable

Changes:

• Added explicit value === null check before typeof comparison
• Removed t === null from typeof checks (impossible condition)

Testing:

• Added comprehensive unit tests (test/isjsonserializable.test.ts)
• Tests cover: null, undefined, strings, numbers, booleans, arrays, objects, FormData, URLSearchParams, buffers
• All 10 tests pass

Summary by CodeRabbit

• Bug Fixes

  • Fixed a bug where null values were incorrectly handled during JSON serialization checks, causing improper processing in downstream operations.

• Tests

  • Added comprehensive test suite validating proper handling of null, undefined, primitives, arrays, objects, and various non-serializable types.

[coderabbitai]

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: 59a05958-495b-4ad3-bbe3-4fb39f77f6f2

📥 Commits

Reviewing files that changed from the base of the PR and between dfbe3ca and f593d42.

📒 Files selected for processing (2)

• src/utils.ts
• test/isjsonserializable.test.ts

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📝 Walkthrough

Walkthrough

Fixes a bug in isJSONSerializable where passing null would fall through to object-handling logic (since typeof null === "object") and throw a TypeError. An explicit value === null guard is added to return true early. A new Vitest test file covers null, primitives, arrays, plain objects, and non-serializable browser types.

Changes

isJSONSerializable null fix and tests

Layer / File(s)	Summary
null guard fix and test coverage src/utils.ts, test/isjsonserializable.test.ts	isJSONSerializable adds an explicit value === null early-return of true, replacing the dead typeof value === null check. New test suite asserts true for null, primitives, arrays, and plain objects, and false for ArrayBuffer, FormData, and URLSearchParams.

Estimated code review effort

🎯 1 (Trivial) | ⏱️ ~3 minutes

Poem

🐇 A null walked in, was turned away,
"Not serializable!" the function would say.
But null IS valid JSON, friend — it's true!
A simple === null check fixes the brew.
Now tests confirm what the spec always knew. ✨

🚥 Pre-merge checks | ✅ 4 | ❌ 1

❌ Failed checks (1 warning)

Check name	Status	Explanation	Resolution
Docstring Coverage	⚠️ Warning	Docstring coverage is 0.00% which is insufficient. The required threshold is 80.00%.	Write docstrings for the functions missing them to satisfy the coverage threshold.

✅ Passed checks (4 passed)

Check name	Status	Explanation
Description Check	✅ Passed	Check skipped - CodeRabbit’s high-level summary is enabled.
Title check	✅ Passed	The title clearly and specifically describes the main fix: handling null values correctly in isJSONSerializable function.
Linked Issues check	✅ Passed	Code changes fully address all objectives from issue #571: null is now explicitly handled, dead code removed, TypeError prevented, and null correctly identified as JSON-serializable.
Out of Scope Changes check	✅ Passed	All changes are directly related to fixing the isJSONSerializable null-handling bug; no unrelated modifications were introduced.

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✨ Finishing Touches

🧪 Generate unit tests (beta)

• Create PR with unit tests

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