fix(runtime-vapor): don't make out-in wait for a branch that left to nothing

[edison1105]

Summary by CodeRabbit

• Bug Fixes
  • Fixed transitions that leave to no content so returning content appears without being held back while the previous content finishes leaving.
  • Prevented content that is still leaving from being removed early when the returning content has a different element or component type.
  • Improved consistency across conditional content, slots, and cached components.

[coderabbitai]

No actionable comments were generated in the recent review. 🎉

ℹ️ Recent review info

⚙️ Run configuration

• Configuration used: defaults
• Review profile: CHILL
• Plan: Advanced
• Run ID: 3e4e6f1a-ea34-4f3f-a289-19c673b166ae

📥 Commits

Reviewing files that changed from the base of the PR and between e291103 and 596a8b4.

📒 Files selected for processing: 3

• packages/runtime-vapor/__tests__/components/Transition.spec.ts
• packages/runtime-vapor/src/components/Transition.ts
• packages/runtime-vapor/src/fragment.ts

Included review availability: This review used your included allowance. Your plan provides up to 10 included reviews per hour; 9 remain after this review.

📝 Walkthrough

DynamicFragment.update now clears an active unpaired leave before considering teardown. New Vapor and VDOM parity tests cover out-in transitions where a branch leaves to no content and returns while its leave is pending.

Changes: Vapor out-in transitions

Layer / File(s)	Summary
Clear unpaired leave before teardown packages/runtime-vapor/src/fragment.ts, packages/runtime-vapor/src/components/Transition.ts	DynamicFragment.update clears leaving and pending before teardown when an unpaired leave is active. Comments describe the unpaired condition in terms of no paired incoming branch or no render.
Test empty-branch transition cases packages/runtime-vapor/__tests__/components/Transition.spec.ts	Parity tests cover direct, slotted, forwarded, conditional-slot, and KeepAlive branches. They also check returns with a different element or component vnode while a leave is pending.

Priority: ⬇️ Low

Estimated code review effort: 2 (Simple) | ~15 minutes

Change: Bug fix

Merge Risk: ⚪ Minimal · up to 596a8

Returning content is not held back by the pending leave, and no issue requiring a fix before merge was identified.

Pre-merge checks: 4 · 1

Failed checks: 1 warning

Check name	Status	Explanation	Resolution
Docstring Coverage		Docstring coverage is 33.33% which is insufficient. The required threshold is 80.00%. Docstring coverage is scoped to functions touched by this diff. Analyzed 3 functions across 3 files.	Write docstrings for the functions missing them to satisfy the coverage threshold.

Passed checks: 4 passed

Check name	Status	Explanation
Description Check		Check skipped - CodeRabbit’s high-level summary is enabled.
Title check		The title clearly and concisely describes the main runtime-vapor fix: preventing an out-in transition from waiting when the leaving branch renders no content.
Linked Issues check		Check skipped because no linked issues were found for this pull request.
Out of Scope Changes check		Check skipped because no linked issues were found for this pull request.

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commit: 596a8b4

[github-actions]

Size Report

Bundles

File	Size	Gzip	Brotli
compiler-dom.global.prod.js	87.4 kB	30.7 kB	27 kB
runtime-dom.global.prod.js	119 kB	44.8 kB	40.2 kB
vue.global.prod.js	180 kB	65.1 kB	58 kB

Usages

Name	Size	Gzip	Brotli
createApp (CAPI only)	54.6 kB	21.2 kB	19.4 kB
createApp	63.5 kB	24.5 kB	22.2 kB
createApp + vaporInteropPlugin	139 kB (+1 B)	50 kB (+3 B)	44.9 kB (+67 B)
createVaporApp	34.2 kB	13.2 kB	12.2 kB
createSSRApp	68.6 kB	26.5 kB	24.1 kB
createVaporSSRApp	41 kB	15.6 kB	14.4 kB
defineCustomElement	70.1 kB	26.5 kB	24.1 kB
defineVaporCustomElement	49.1 kB	18 kB	16.5 kB
overall	79.1 kB	30.1 kB	27.2 kB