fix(runtime-core): restore SSR setup state when handling async setup result

[cernymatej]

fix #15113

this should fix a problem where regular watchers were being created on the server for Options API components with async setup()

and also a potential memory leak since SSR never unmounts and such a watcher is never stopped... if it depends on request-outliving state, it retains the whole component instance and through it the whole app

Summary by CodeRabbit

• Bug Fixes
  • Improved server-side rendering reliability for components using asynchronous setup.
  • Prevented watchers from being created or retained unexpectedly during server-side rendering.
  • Reduced potential memory retention after repeated server-rendered requests.

[coderabbitai]

📝 Walkthrough

Walkthrough

SSR async setup() resolution now preserves SSR setup state while processing results and reliably restores it. Regression tests verify option-API watchers are not created and rendered apps are garbage-collected.

Changes

SSR async setup watcher lifecycle

Layer / File(s)	Summary
Preserve SSR setup state during async resolution packages/runtime-core/src/component.ts	The async setup Promise handler enables SSR setup state while handling the resolved result and disables it in a finally block.
Validate watcher suppression and garbage collection packages/server-renderer/__tests__/ssrWatch.spec.ts	Regression tests verify that async setup does not create option-API watchers and that rendered apps are released after garbage collection.

Estimated code review effort: 2 (Simple) | ~10 minutes

Possibly related PRs

• vuejs/core#14547: Both changes preserve SSR setup state across async setup boundaries.

Suggested labels: scope: ssr, :hammer: p3-minor-bug

Suggested reviewers: edison1105

🚥 Pre-merge checks | ✅ 5

✅ Passed checks (5 passed)

Check name	Status	Explanation
Linked Issues check	✅ Passed	The code and tests address #15113 by preventing SSR watchers from being created and retained for async setup components.
Out of Scope Changes check	✅ Passed	The changes stay focused on the SSR async setup watcher leak fix and its regression tests.
Docstring Coverage	✅ Passed	No functions found in the changed files to evaluate docstring coverage. Skipping docstring coverage check.
Description Check	✅ Passed	Check skipped - CodeRabbit’s high-level summary is enabled.
Title check	✅ Passed	The title accurately describes the runtime-core SSR async setup state fix, which is the main code change in the PR.

✨ Finishing Touches

🧪 Generate unit tests (beta)

• Create PR with unit tests

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[pkg-pr-new]

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@vue/compiler-core

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@vue/compiler-dom

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@vue/compiler-ssr

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@vue/reactivity

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@vue/runtime-core

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@vue/runtime-dom

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@vue/server-renderer

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@vue/shared

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vue

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commit: 31ff39d

[github-actions]

Size Report

Bundles

File	Size	Gzip	Brotli
runtime-dom.global.prod.js	107 kB (+25 B)	40.5 kB (+12 B)	36.3 kB (+31 B)
vue.global.prod.js	166 kB (+25 B)	60.6 kB (+12 B)	53.8 kB (+22 B)

Usages

Name	Size	Gzip	Brotli
createApp (CAPI only)	49.2 kB (+27 B)	19.1 kB (+12 B)	17.5 kB (+15 B)
createApp	57.4 kB (+27 B)	22.2 kB (+14 B)	20.3 kB (+13 B)
createSSRApp	61.9 kB (+27 B)	24.1 kB (+18 B)	22 kB (+17 B)
defineCustomElement	63.6 kB (+27 B)	24.1 kB (+14 B)	22 kB (+16 B)
overall	72 kB (+25 B)	27.5 kB (+11 B)	25 kB (+4 B)

[edison1105]

/ecosystem-ci run

[vue-bot]

📝 Ran ecosystem CI: Open

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