fix(types): prevent shallowReactive marker from leaking into value unions

[edison1105]

close #14490

Summary by CodeRabbit

• Bug Fixes
  • Fixed shallow-reactive type behavior to prevent marker propagation into union types, improving type compatibility for shallow reactive values.
• Tests
  • Added a test that verifies the shallow-reactive marker does not leak into union-typed values.

[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: c9e3288a-1a02-4216-8274-c2eacb2a74a6

📥 Commits

Reviewing files that changed from the base of the PR and between 59d53ec and 1f76692.

📒 Files selected for processing (1)

• packages/reactivity/src/ref.ts

---

📝 Walkthrough

Walkthrough

Change ShallowReactive's marker type from an optional boolean to a required never and adjust UnwrapRefSimple's object-branching to prevent the shallow-reactive marker from leaking into union/value unwrapping; added a dts test asserting the marker no longer appears in unions.

Changes

Cohort / File(s)	Summary
ShallowReactive type packages/reactivity/src/reactive.ts	Changed ShallowReactive<T> marker from [ShallowReactiveMarker]?: true to [ShallowReactiveMarker]: never.
Unwrap/ref logic packages/reactivity/src/ref.ts	Updated UnwrapRefSimple<T> branching: objects with required ShallowReactiveMarker now short-circuit to T, while other objects follow the previous property-unwrapping mapping.
Tests (dts) packages-private/dts-test/reactivity.test-d.ts	Added test "shallowReactive marker should not leak into value unions" and imported shallowReactive to verify the marker is not present in derived union types.

Estimated code review effort

🎯 3 (Moderate) | ⏱️ ~20 minutes

Possibly related PRs

• fix(reactivity): toRef edge cases for ref unwrapping #12420: Modifies reactivity unwrapping/type-level logic for shallowReactive in ref.ts/reactive.ts.

Suggested labels

ready to merge, scope: reactivity, :cake: p2-nice-to-have

Poem

🐰 I nudged a tiny marker into "never" land,
So unions breathe easy and types now stand.
No more stray true in the type parade,
Shallow paths stay shallow — a carrot parade! 🥕

🚥 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 directly addresses the main change: preventing the shallowReactive marker from leaking into value unions, which is the core objective of the PR.
Linked Issues check	✅ Passed	The PR implements the required type changes to prevent ShallowReactiveMarker from leaking into value unions used by v-for, addressing all objectives from issue #14490.
Out of Scope Changes check	✅ Passed	All changes are scoped to fixing the type inference issue: ShallowReactive marker type redefinition, UnwrapRefSimple logic adjustment, and a corresponding test case.
Docstring Coverage	✅ Passed	No functions found in the changed files to evaluate docstring coverage. Skipping docstring coverage check.

_{✏️ Tip: You can configure your own custom pre-merge checks in the settings.}

✨ Finishing Touches

📝 Generate docstrings

• Create stacked PR
• Commit on current branch

🧪 Generate unit tests (beta)

• Create PR with unit tests
• Commit unit tests in branch edison/fix/14490

---

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

[github-actions]

Size Report

Bundles

File	Size	Gzip	Brotli
runtime-dom.global.prod.js	105 kB	39.8 kB	35.8 kB
vue.global.prod.js	164 kB	59.8 kB	53.2 kB

Usages

Name	Size	Gzip	Brotli
createApp (CAPI only)	48.3 kB	18.8 kB	17.2 kB
createApp	56.5 kB	21.8 kB	19.9 kB
createSSRApp	60.7 kB	23.6 kB	21.5 kB
defineCustomElement	62.6 kB	23.8 kB	21.7 kB
overall	71 kB	27.2 kB	24.8 kB

[pkg-pr-new]

Open in StackBlitz

@vue/compiler-core

pnpm add https://pkg.pr.new/@vue/compiler-core@14493

npm i https://pkg.pr.new/@vue/compiler-core@14493

yarn add https://pkg.pr.new/@vue/compiler-core@14493.tgz

@vue/compiler-dom

pnpm add https://pkg.pr.new/@vue/compiler-dom@14493

npm i https://pkg.pr.new/@vue/compiler-dom@14493

yarn add https://pkg.pr.new/@vue/compiler-dom@14493.tgz

@vue/compiler-sfc

pnpm add https://pkg.pr.new/@vue/compiler-sfc@14493

npm i https://pkg.pr.new/@vue/compiler-sfc@14493

yarn add https://pkg.pr.new/@vue/compiler-sfc@14493.tgz

@vue/compiler-ssr

pnpm add https://pkg.pr.new/@vue/compiler-ssr@14493

npm i https://pkg.pr.new/@vue/compiler-ssr@14493

yarn add https://pkg.pr.new/@vue/compiler-ssr@14493.tgz

@vue/reactivity

pnpm add https://pkg.pr.new/@vue/reactivity@14493

npm i https://pkg.pr.new/@vue/reactivity@14493

yarn add https://pkg.pr.new/@vue/reactivity@14493.tgz

@vue/runtime-core

pnpm add https://pkg.pr.new/@vue/runtime-core@14493

npm i https://pkg.pr.new/@vue/runtime-core@14493

yarn add https://pkg.pr.new/@vue/runtime-core@14493.tgz

@vue/runtime-dom

pnpm add https://pkg.pr.new/@vue/runtime-dom@14493

npm i https://pkg.pr.new/@vue/runtime-dom@14493

yarn add https://pkg.pr.new/@vue/runtime-dom@14493.tgz

@vue/server-renderer

pnpm add https://pkg.pr.new/@vue/server-renderer@14493

npm i https://pkg.pr.new/@vue/server-renderer@14493

yarn add https://pkg.pr.new/@vue/server-renderer@14493.tgz

@vue/shared

pnpm add https://pkg.pr.new/@vue/shared@14493

npm i https://pkg.pr.new/@vue/shared@14493

yarn add https://pkg.pr.new/@vue/shared@14493.tgz

vue

pnpm add https://pkg.pr.new/vue@14493

npm i https://pkg.pr.new/vue@14493

yarn add https://pkg.pr.new/vue@14493.tgz

@vue/compat

pnpm add https://pkg.pr.new/@vue/compat@14493

npm i https://pkg.pr.new/@vue/compat@14493

yarn add https://pkg.pr.new/@vue/compat@14493.tgz

commit: 1f76692

[edison1105]

/ecosystem-ci run

[vue-bot]

📝 Ran ecosystem CI: Open

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