fix(teleport): skip child unmount when pending mount discarded (#14876)

[pont1s]

close #14876

Summary by CodeRabbit

• Bug Fixes

  • Resolved an issue where deferred teleports inside Suspense could attempt to mount or unmount discarded content when removed before completion, preventing stray or duplicate DOM updates.

• Tests

  • Added regression tests covering Suspense + deferred Teleport scenarios to ensure discarded teleports never mount their content and resolved Suspense output is correct.

[coderabbitai]

📝 Walkthrough

Walkthrough

Fix Teleport removal for deferred mounts: queued pending teleport mounts are disposed and removed from pendingMounts, and child unmount/target cleanup is skipped when the teleport never mounted. Added two regression tests that assert discarded teleports with component children never mount.

Changes

Teleport + Suspense deferred mount fix

Layer / File(s)	Summary
Deferred teleport removal fix packages/runtime-core/src/components/Teleport.ts	TeleportImpl.remove() detects queued pending mounts in pendingMounts, marks the queued scheduler job DISPOSED, deletes it from pendingMounts, and avoids unmounting array children when a pending mount exists.
Regression test coverage packages/runtime-core/__tests__/components/Suspense.spec.ts, packages/runtime-core/__tests__/components/Teleport.spec.ts	Added two tests for #14876 validating that a Teleport (with a component child) discarded before its deferred mount does not mount into the target and does not cause unmount crashes.

🎯 3 (Moderate) | ⏱️ ~20 minutes

Possibly related PRs

• vuejs/core#14600: Modifies packages/runtime-core/src/components/Teleport.ts and touches removal/anchor cleanup logic similar to this change.
• vuejs/core#14702: Added pending-mount guards for teleport movement; related to deferred-mount handling extended here.
• vuejs/core#14642: Introduced pendingMounts mechanism to defer teleport mounting inside Suspense, which this PR now accounts for during removal.

Suggested labels

scope: teleport, scope: suspense, :hammer: p3-minor-bug

Suggested reviewers

• edison1105

Poem

🐰 A queued mount waited in the night,
Disposed with care before it took flight.
No stray component now hops in by chance,
Suspense and Teleport keep a tidy dance.
Hooray — no crash, just peaceful advance.

🚥 Pre-merge checks | ✅ 5

✅ Passed checks (5 passed)

Check name	Status	Explanation
Description Check	✅ Passed	Check skipped - CodeRabbit’s high-level summary is enabled.
Linked Issues check	✅ Passed	The pull request adds regression tests and fixes the TeleportImpl.remove() method to guard against unmounting children with null components when pending mounts are discarded, directly addressing all stated requirements in issue #14876.
Out of Scope Changes check	✅ Passed	All changes (two regression tests and one implementation fix in TeleportImpl.remove) are directly scoped to fixing the pending mount unmount crash described in issue #14876.
Docstring Coverage	✅ Passed	No functions found in the changed files to evaluate docstring coverage. Skipping docstring coverage check.
Title check	✅ Passed	The title clearly and specifically describes the main fix: preventing child unmount when a pending teleport mount is discarded, directly addressing issue #14876.

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✨ Finishing Touches

🧪 Generate unit tests (beta)

• Create PR with unit tests

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[Copilot]

Pull request overview

Note

Copilot was unable to run its full agentic suite in this review.

Fixes Teleport unmount behavior for deferred teleports that are discarded before their queued mount effect runs (notably within Suspense), and adds regression tests for component children.

Changes:

• Adjust Teleport removal logic to dispose pending mount jobs and return early for discarded deferred teleports.
• Ensure placeholder cleanup occurs when a discarded deferred teleport is being removed.
• Add regression tests covering discarded deferred teleports with component children (both DOM renderer and Suspense cases).

Reviewed changes

Copilot reviewed 3 out of 3 changed files in this pull request and generated 2 comments.

File	Description
packages/runtime-core/src/components/Teleport.ts	Updates discard/unmount flow for deferred teleports with pending mount jobs.
packages/runtime-core/tests/components/Teleport.spec.ts	Adds DOM-renderer regression test for discarded deferred teleport with component child.
packages/runtime-core/tests/components/Suspense.spec.ts	Adds Suspense regression test ensuring discarded teleport with component child is not mounted on resolve.

---

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[pont1s]

Switched to a guard around the children loop, no early return now. FWIW the leak concern wouldn't have applied either way:

• vnode.el is removed by the renderer's outer remove(vnode) at renderer.ts:2221,
• after TeleportImpl.remove returns

[pont1s]

This mirrors the existing test at line 243 (should not mount discarded teleport after deferred updates) and the other defer-mode tests in this file.

[pkg-pr-new]

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commit: 90743d7

[edison1105]

/ecosystem-ci run

[vue-bot]

📝 Ran ecosystem CI: Open

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