RFC: unwrapFragment to flatten nested Fragment nodes

[baozjj]

Summary

This RFC proposes introducing an internal utility function unwrapFragment in @vue/runtime-core, which recursively flattens Fragment nodes from a VNode array. This solves a practical problem where multiple nested Fragment layers—introduced by slot forwarding across components—make it difficult to inspect or reason about slot content.

Example Use Case

const rawContent = slots.default?.()
const children = unwrapFragment(rawContent)
console.log(children.length) // now reflects real slot content

This is especially useful in component libraries like TDesign, where internal logic depends on the slot node length or type—for example, to determine whether to show a "collapse/expand" toggle based on number of child nodes. In nested usage, the slots are wrapped in an extra Fragment, leading to incorrect logic.

This utility simplifies advanced component use cases without altering Vue’s core slot behavior or introducing new user-facing API surface.

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Links

• Full Rendered Proposal
• Discussion Thread

• Related PR in vue-next: unwrapFragment test case and motivation

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Important: Do NOT comment on this PR. Please use the discussion thread linked above to provide feedback, as it provides branched discussions that are easier to follow. This also makes the edit history of the PR clearer.