fix(types): support exact optional public props

[ifer47]

This PR fixes the exactOptionalPropertyTypes regression around defineProps spreads by widening the public $props surface for optional keys while keeping internal toRefs behavior intact. It adds a dedicated exact-optional dts fixture and tsconfig, and passes pnpm test-dts-only.

Fixes #14366.

Summary by CodeRabbit

• Tests

  • Added new type-checking coverage for Vue component optional props when exactOptionalPropertyTypes is enabled.
  • Extended the DTS-only test run to include an additional strict TypeScript compilation pass.

• Chores / Type Improvements

  • Improved the public-facing component $props typing to better preserve optional-prop behavior under strict TypeScript settings, including components with default prop values.

[coderabbitai]

📝 Walkthrough

Walkthrough

Introduces a LooseOptional<T> type helper in componentPublicInstance.ts that remaps optional prop keys to allow undefined, then applies it to ComponentPublicInstance.$props. Adds a new tsconfig enabling exactOptionalPropertyTypes and a matching type-test file, wired into the test-dts-only npm script.

Changes

exactOptionalPropertyTypes $props fix

Layer / File(s)	Summary
LooseOptional helper and $props update packages/runtime-core/src/componentPublicInstance.ts	Adds LooseOptional<T> generic that maps optional prop keys to T[K] | undefined, with an IfAny fallback. Updates ComponentPublicInstance.$props on both sides of the MakeDefaultsOptional conditional to wrap P with LooseOptional<P>.
Type test infrastructure packages-private/dts-test/tsconfig.exactOptionalPropertyTypes.json, packages-private/dts-test/exactOptionalPropertyTypes.test-d.tsx, package.json	Adds a dedicated tsconfig extending tsconfig.test.json with exactOptionalPropertyTypes: true. New type test defines Child and WithDefault Vue components with optional foo props and asserts JSX.Element for spread props and explicit foo={undefined} scenarios. Updates test-dts-only script to run the new tsconfig project.

Estimated code review effort

🎯 2 (Simple) | ⏱️ ~10 minutes

Possibly related PRs

• vuejs/core#12870: Both PRs modify TypeScript typing for component instance $props—this PR loosens optional prop keys via LooseOptional<P> in componentPublicInstance.ts, while that PR addresses component instance resolution in component.ts.

Suggested labels

scope: types

Suggested reviewers

• jh-leong
• edison1105
• KazariEX

Poem

🐇 A prop of type optional, uncertain and wide,
undefined once barred — now welcomed inside.
LooseOptional hops in with a wiggle and glee,
spreading its types so the JSX runs free.
No more strict errors to ruffle this hare! 🌿

🚥 Pre-merge checks | ✅ 5

✅ Passed checks (5 passed)

Check name	Status	Explanation
Title check	✅ Passed	The title clearly and specifically describes the main change: adding support for exact optional properties in the public prop types, which aligns with the primary objective of fixing a regression related to exactOptionalPropertyTypes.
Docstring Coverage	✅ Passed	No functions found in the changed files to evaluate docstring coverage. Skipping docstring coverage check.
Linked Issues check	✅ Passed	Check skipped because no linked issues were found for this pull request.
Out of Scope Changes check	✅ Passed	Check skipped because no linked issues were found for this pull request.
Description Check	✅ Passed	Check skipped - CodeRabbit’s high-level summary is enabled.

✨ Finishing Touches

🧪 Generate unit tests (beta)

• Create PR with unit tests

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commit: bc2d402

[github-actions]

Size Report

Bundles

File	Size	Gzip	Brotli
runtime-dom.global.prod.js	106 kB	40.2 kB	36.1 kB
vue.global.prod.js	164 kB	60.2 kB	53.5 kB

Usages

Name	Size	Gzip	Brotli
createApp (CAPI only)	48.8 kB	19 kB	17.4 kB
createApp	56.9 kB	22 kB	20.1 kB
createSSRApp	61.2 kB	23.8 kB	21.7 kB
defineCustomElement	63.1 kB	23.9 kB	21.8 kB
overall	71.7 kB	27.4 kB	25 kB

[edison1105]

Thanks for the fix. I found one remaining exactOptionalPropertyTypes hole around defaulted props.

[ifer47]

@edison1105 The remaining defaulted-props case was addressed in bc2d402 and the review thread is resolved. CI is green now. Could you take another look when you have a chance? Thanks!