types(defineProps): avoid never props becoming boolean flags

[edison1105]

close #14056

Summary by CodeRabbit

• Tests

  • Added test coverage verifying type behavior when a prop is declared as never, ensuring regressions are caught.

• Bug Fixes

  • Improved TypeScript inference for optional boolean props used with defineProps, providing stricter and more accurate editor hints and fewer incorrect type widenings.

[coderabbitai]

Walkthrough

Refines a conditional type used to detect boolean-like prop keys and adds a type test ensuring props declared as never are handled correctly by defineProps.

Changes

Cohort / File(s)	Change Summary
Test additions packages-private/dts-test/setupHelpers.test-d.ts	Adds a new test block "defineProps w/ never prop" asserting foo?: never yields `never
Type narrowing packages/runtime-core/src/apiSetupHelpers.ts	Changes BooleanKey<T> conditional to further check `T[K] extends boolean

Sequence Diagram(s)

sequenceDiagram
    participant Dev as defineProps call site
    participant BooleanKey as BooleanKey<T>
    participant TS as TypeScript resolver

    Note over Dev,TS: Type selection for each prop key
    Dev->>BooleanKey: provide prop type T[K]
    BooleanKey->>TS: evaluate "T[K] extends boolean | undefined?"
    TS-->>BooleanKey: yes/no
    alt matches boolean|undefined
        BooleanKey->>TS: evaluate "T[K] extends never | undefined?"
        TS-->>BooleanKey: yes -> exclude key
        TS-->>BooleanKey: no  -> include key
    else does not match
        BooleanKey-->>Dev: exclude key
    end

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Estimated code review effort

🎯 3 (Moderate) | ⏱️ ~20 minutes

• Key areas for attention:
  • Correctness of the nested conditional type in BooleanKey<T> (verify behavior with never, optional, and unions like boolean | undefined/boolean | null)
  • The new test covers the reported edge case; consider additional tests for required booleans and boolean unions
  • Confirm no unintended regressions in other type branches that rely on BooleanKey

Suggested reviewers

• KazariEX
• johnsoncodehk

Poem

🐰 A hop of types beneath the moonlit test,
Never hid from props — now checked and dressed.
Boolean keys pruned clean with gentle cheer,
The rabbit stamps approval — types are clear!

Pre-merge checks and finishing touches

✅ 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 clearly describes the main change: fixing a typing issue where never props incorrectly become boolean flags in defineProps.
Linked Issues check	✅ Passed	The PR addresses the core issue (#14056) by refining the BooleanKey type to exclude never props from being treated as boolean flags, which directly resolves the reported typing problem.
Out of Scope Changes check	✅ Passed	All changes are directly scoped to fixing the reported issue: a type refinement in apiSetupHelpers.ts and a corresponding test in the test file.
Docstring Coverage	✅ Passed	No functions found in the changed files to evaluate docstring coverage. Skipping docstring coverage check.

✨ Finishing touches

• 📝 Generate docstrings

🧪 Generate unit tests (beta)

• Create PR with unit tests
• Post copyable unit tests in a comment
• Commit unit tests in branch edison/fix/14056

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📜 Recent review details

Configuration used: CodeRabbit UI

Review profile: CHILL

Plan: Pro

📥 Commits

Reviewing files that changed from the base of the PR and between 0600862 and 6079bdb.

📒 Files selected for processing (1)

• packages/runtime-core/src/apiSetupHelpers.ts (1 hunks)

🚧 Files skipped from review as they are similar to previous changes (1)

• packages/runtime-core/src/apiSetupHelpers.ts

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Size Report

Bundles

File	Size	Gzip	Brotli
runtime-dom.global.prod.js	103 kB	38.9 kB	35 kB
vue.global.prod.js	161 kB	58.8 kB	52.4 kB

Usages

Name	Size	Gzip	Brotli
createApp (CAPI only)	46.9 kB	18.3 kB	16.8 kB
createApp	55 kB	21.4 kB	19.6 kB
createSSRApp	59.3 kB	23.1 kB	21.1 kB
defineCustomElement	60.6 kB	23.1 kB	21.1 kB
overall	69.3 kB	26.6 kB	24.3 kB

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commit: 6079bdb