fix(runtime): keep clone-only message reads read-only, and see an uncloneable brand created mid-clone

[adrian-niculescu]

An object marked with markAsUncloneable from a getter, during the clone that reaches it, is cloned instead of throwing DataCloneError when that is the first markAsUncloneable call in the isolate. The serializer reads the brand once, when it is constructed, and at that point the brand does not exist yet. It now picks the brand up once markAsUncloneable creates it.

Separately, SerializedValue::Deserialize cleared its transfer vectors on every read. A clone-only message is read by every BroadcastChannel receiver, and every getEnvironmentData call, with no lock, so those clears were concurrent writes to shared state, against what the comment on the consumed_ flag intends. Only the single receiver of a message with transferables writes them now.

Stacked on #2043; the same fix for iOS is NativeScript/ios#490. The new markAsUncloneable spec fails on that branch and passes here, and the full device suite passes. The deserialization race has no deterministic spec.

Summary by CodeRabbit

• Bug Fixes
  • Structured cloning now correctly reports a DataCloneError when it encounters an object marked as uncloneable during serialization.
  • Deserialized values with transferables remain single-use, while values without transferables can be read without triggering transferable cleanup.

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ℹ️ Recent review info

⚙️ Run configuration

• Configuration used: Repository UI
• Review profile: CHILL
• Plan: Advanced
• Run ID: 251f22e8-9341-43d9-9993-1b569a175846

📥 Commits

Reviewing files that changed from the base of the PR and between 42a8bcf and cf36bd1.

📒 Files selected for processing (3)

• test-app/app/src/main/assets/app/tests/messaging/uncloneableInGetterWorker.js
• test-app/app/src/main/assets/app/tests/testMessaging.js
• test-app/runtime/src/main/cpp/StructuredSerialization.cpp

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📝 Walkthrough

Walkthrough

The change updates structured serialization to detect an uncloneable brand created while a getter runs during cloning, and to apply single-consumer handling and transferable-storage cleanup only when transferables are present. It adds a worker regression test for the clone error.

Changes

Structured serialization

Layer / File(s)	Summary
Detect brands created during cloning test-app/runtime/src/main/cpp/StructuredSerialization.cpp, test-app/app/src/main/assets/app/tests/messaging/uncloneableInGetterWorker.js, test-app/app/src/main/assets/app/tests/testMessaging.js	IsHostObject refreshes an empty cached uncloneable brand. A worker regression test checks that marking an object uncloneable from a getter causes a DataCloneError.
Condition cleanup on transferables test-app/runtime/src/main/cpp/StructuredSerialization.cpp	Deserialize uses the presence of transferables to control single-consumer marking and cleanup of transferred buffer and port storage.

Priority: ➖ Normal

Estimated code review effort: 2 (Simple) | ~12 minutes

Change: Bug fix

Suggested reviewers: edusperoni

Merge Risk: ⚪ Minimal · up to cf36b

No merge-blocking issue is established; the change is ready to merge after normal checks.

🚥 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%. Docstring coverage is scoped to functions touched by this diff. Analyzed 2 functions across 3 files.	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 describes both main runtime fixes: read-only clone-only message reads and detection of an uncloneable brand created during cloning.
Linked Issues check	✅ Passed	Check skipped because no linked issues were found for this pull request.
Out of Scope Changes check	✅ Passed	Check skipped because no linked issues were found for this pull request.

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_{A rabbit watched the getter run,
Then saw the clone report its error.
With transferables, storage clears;
Without them, vectors stay in place.
The rabbit hops through tests with cheer.}

_{Comment @coderabbitai help to get the list of available commands.}

[adrian-niculescu]

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