fix(shared): handle circular references in looseEqual by ondrhn · Pull Request #15499 · vuejs/core

ondrhn · 2026-09-13T17:37:45Z

Since #15328 looseEqual recurses into the entries of Maps and Sets, so a <select v-model> whose option values are Sets of mutually referencing objects throws RangeError: Maximum call stack size exceeded during mount. The same recursion already existed for plain objects and arrays with cycles.

looseEqual now keeps a stack of the object pairs currently being compared and passes it through the recursive calls. When a pair is met again on the way down it is treated as equal (the same approach as lodash's isEqual), so cyclic structures terminate and structurally identical cyclic Maps/Sets/objects/arrays compare equal. The entry is removed once the pair has been compared, so shared (non-cyclic) references are unaffected.

Tested with pnpm vitest run packages/shared/__tests__/looseEqual.spec.ts packages/runtime-dom/__tests__/directives/vModel.spec.ts and pnpm run test-unit.

Summary by CodeRabbit

Bug Fixes
- Improved equality comparisons for circular and self-referential objects.
- More accurately handles shared references and nested Maps, Sets, arrays, and objects.
- Prevents incorrectly treating differently structured circular references as equal.
Tests
- Added coverage confirming circular-reference comparisons produce consistent results in both directions.

coderabbitai · 2026-09-13T17:37:59Z

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📒 Files selected for processing (2)

packages/shared/__tests__/looseEqual.spec.ts
packages/shared/src/looseEqual.ts

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packages/shared/tests/looseEqual.spec.ts
packages/shared/src/looseEqual.ts

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📝 Walkthrough

Walkthrough

looseEqual now tracks active object pairings in both directions during recursive comparisons. Arrays, Maps, Sets, and objects propagate this state. Tests cover circular collections, self-containing Sets, shared references, and asymmetric cycles.

Changes

Cycle-safe loose equality

Layer / File(s)	Summary
Cycle pair tracking `packages/shared/src/looseEqual.ts`	`looseEqual` uses `ComparisonState` to record both operand directions, reject conflicting active pairings, and clean up state after comparison.
Nested comparison propagation and validation `packages/shared/src/looseEqual.ts`, `packages/shared/__tests__/looseEqual.spec.ts`	Array, Map, Set, and object comparisons pass the bidirectional state through recursive calls. Tests cover circular collections, self-referential Sets, shared references, and asymmetric cycles.

Priority: ➖ Normal

Estimated code review effort: 3 (Moderate) | ~20 minutes

Change: Bug fix · Severity of issue fixed: Medium

Merge Risk: ⚪ Minimal · up to e74c5

The cycle-safe comparison paths cover arrays, objects, Maps, and Sets without leaving an identified regression. The change is ready to merge.

🚥 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 5 functions across 2 files.	Write docstrings for the functions missing them to satisfy the coverage threshold.

✅ Passed checks (4 passed)

Check name	Status	Explanation
Linked Issues check	✅ Passed	The changes satisfy issue `#15496`. `looseCompareNested` tracks active object pairs in both directions and returns `false` when either operand maps to a different active counterpart. It removes pairs af…
Out of Scope Changes check	✅ Passed	The changes are limited to `packages/shared/src/looseEqual.ts` and `packages/shared/__tests__/looseEqual.spec.ts`. The source change implements cycle-safe comparison for the linked issue. The tests ve…
Description Check	✅ Passed	Check skipped - CodeRabbit’s high-level summary is enabled.
Title check	✅ Passed	The title clearly and concisely describes the main change: fixing circular-reference handling in `looseEqual`.

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Inline comments:
In `@packages/shared/src/looseEqual.ts`:
- Around line 68-83: Update looseCompareNested to track active comparisons in
both directions, rejecting a comparison when the right-hand value is already
paired with a different active left-hand value; preserve the existing
seen.has(a) handling and seen.delete(a) cleanup so cyclic structure comparisons
retain their established behavior.

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📒 Files selected for processing (2)

packages/shared/__tests__/looseEqual.spec.ts
packages/shared/src/looseEqual.ts

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pkg-pr-new · 2026-09-14T01:58:10Z

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commit: e74c50d

github-actions · 2026-09-14T01:59:12Z

Size Report

Bundles

File	Size	Gzip	Brotli
runtime-dom.global.prod.js	109 kB (+234 B)	41.2 kB (+102 B)	36.9 kB (+93 B)
vue.global.prod.js	168 kB (+234 B)	61.4 kB (+104 B)	54.5 kB (+56 B)

Usages

Name	Size	Gzip	Brotli
createApp (CAPI only)	50.5 kB (+239 B)	19.5 kB (+83 B)	17.9 kB (+90 B)
createApp	58.6 kB (+229 B)	22.6 kB (+124 B)	20.7 kB (+101 B)
createSSRApp	63.4 kB (+237 B)	24.6 kB (+112 B)	22.4 kB (+109 B)
defineCustomElement	64.9 kB (+223 B)	24.5 kB (+102 B)	22.4 kB (+85 B)
overall	73.2 kB (+234 B)	27.9 kB (+83 B)	25.4 kB (+134 B)

edison1105 · 2026-09-16T12:49:25Z

/ecosystem-ci run

vue-bot · 2026-09-16T13:11:51Z

📝 Ran ecosystem CI: Open

suite	result	latest scheduled
language-tools	❌ failure	❌ failure
pinia	✅ success	✅ success
test-utils	✅ success	✅ success
vite-plugin-vue	✅ success	✅ success
radix-vue	✅ success	✅ success
quasar	✅ success	✅ success
vuetify	✅ success	❌ failure
primevue	✅ success	✅ success
vue-macros	✅ success	✅ success
vue-simple-compiler	✅ success	✅ success
nuxt	✅ success	✅ success
router	✅ success	✅ success
vitepress	✅ success	✅ success
vue-i18n	✅ success	✅ success
vant	✅ success	✅ success
vueuse	✅ success	✅ success

fix(shared): handle circular references in looseEqual

1fa2c68

coderabbitai Bot reviewed Sep 13, 2026

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Comment thread packages/shared/src/looseEqual.ts

edison1105 changed the title ~~fix(shared): handle circular references in looseEqual (fix #15496)~~ fix(shared): handle circular references in looseEqual Sep 14, 2026

fix(shared): ensure symmetric cycle detection in looseEqual

e74c50d

edison1105 added ready to merge The PR is ready to be merged. 🔨 p3-minor-bug Priority 3: this fixes a bug, but is an edge case that only affects very specific usage. labels Sep 14, 2026

edison1105 merged commit 718f782 into vuejs:main Sep 17, 2026
18 of 19 checks passed

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fix(shared): handle circular references in looseEqual - #15499

fix(shared): handle circular references in looseEqual#15499
edison1105 merged 2 commits into
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ondrhn:fix/loose-equal-circular

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