fix(reactivity): avoid triggering effects when set fails

[ifer47]

This fixes a small reactivity edge case where MutableReactiveHandler.set triggered effects even when the underlying Reflect.set operation failed.

For example, assigning to a non-writable property through a reactive proxy throws and leaves the value unchanged, but the dependent effect was still re-run.

The handler now only triggers ADD / SET notifications when Reflect.set succeeds.

Tests added:

• failed set operation should not trigger effects

Validation:

• pnpm exec vitest run packages/reactivity/__tests__/reactive.spec.ts -t "failed set operation should not trigger effects"
• pnpm exec vitest run packages/reactivity
• pnpm exec prettier --check packages/reactivity/src/baseHandlers.ts packages/reactivity/__tests__/reactive.spec.ts
• pnpm exec eslint packages/reactivity/src/baseHandlers.ts packages/reactivity/__tests__/reactive.spec.ts
• pnpm check

Summary by CodeRabbit

• Bug Fixes

  • Fixed the reactivity system to prevent triggering updates when property assignments fail on protected or read-only properties, ensuring correct state management.

• Tests

  • Added test coverage to verify that failed property assignments do not trigger dependent updates and that cached values remain unchanged.

[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: 98fb573c-8aa2-40f5-943d-3c881b8e2f75

📥 Commits

Reviewing files that changed from the base of the PR and between 478e3e8 and 4c93505.

📒 Files selected for processing (2)

• packages/reactivity/__tests__/reactive.spec.ts
• packages/reactivity/src/baseHandlers.ts

---

📝 Walkthrough

Walkthrough

MutableReactiveHandler.set in baseHandlers.ts now checks that Reflect.set returned a truthy result before calling trigger. A new test in reactive.spec.ts covers the non-writable property case, asserting that a failed assignment throws TypeError and does not cause dependent effects to re-run.

Changes

Reactive trigger guard fix

Layer / File(s)	Summary
Guard trigger on Reflect.set success + non-writable test packages/reactivity/src/baseHandlers.ts, packages/reactivity/__tests__/reactive.spec.ts	The trigger call in MutableReactiveHandler.set is now gated on result being truthy, so ADD/SET triggers are suppressed when the underlying property write fails. The new test defines a writable: false property on a reactive object, asserts the assignment throws TypeError, and confirms the effect's observed value and run count remain unchanged.

Estimated code review effort

🎯 2 (Simple) | ⏱️ ~5 minutes

Suggested labels

ready to merge, scope: reactivity, :hammer: p3-minor-bug

Suggested reviewers

• edison1105

Poem

🐇 A property locked, non-writable, tight,
The effect stayed calm, didn't trigger that night.
One result check added, so small, yet so true,
No phantom re-runs when the write falls through.
Hop hop, little fix — the reactive holds right! 🌿

🚥 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 clearly and concisely describes the main change: preventing effects from being triggered when a set operation fails on a reactive object.
Docstring Coverage	✅ Passed	No functions found in the changed files to evaluate docstring coverage. Skipping docstring coverage check.
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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✨ Finishing Touches

🧪 Generate unit tests (beta)

• Create PR with unit tests

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[github-actions]

Size Report

Bundles

File	Size	Gzip	Brotli
runtime-dom.global.prod.js	106 kB (+3 B)	40.2 kB (+2 B)	36.1 kB (+1 B)
vue.global.prod.js	164 kB (+3 B)	60.2 kB (+4 B)	53.5 kB (+27 B)

Usages

Name	Size	Gzip	Brotli
createApp (CAPI only)	48.8 kB (+3 B)	19 kB	17.4 kB (+3 B)
createApp	56.9 kB (+3 B)	22 kB (-1 B)	20.1 kB (+4 B)
createSSRApp	61.2 kB (+3 B)	23.8 kB	21.7 kB
defineCustomElement	63.1 kB (+3 B)	23.9 kB (-1 B)	21.8 kB (+9 B)
overall	71.7 kB (+3 B)	27.4 kB	25 kB (+57 B)

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commit: 4c93505