fix(nuxt): support v-slot:fallback longform syntax in <DevOnly>

[Mini-ghost]

🔗 Linked issue

N/A

📚 Description

<DevOnly> previously supported only the shorthand slot syntax #fallback. This PR extends support to the longform v-slot:fallback syntax.

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Walkthrough

The DevOnlyPlugin transform in packages/nuxt/src/core/plugins/dev-only.ts now recognises the fallback slot via three syntaxes: fallback, #fallback, and v-slot:fallback. It also changes how the replacement slice start is computed, using fallback.loc.at(-1).start instead of array length indexing. No other logic, control flow, or exported declarations were altered.

Estimated code review effort

🎯 2 (Simple) | ⏱️ ~10 minutes

Pre-merge checks and finishing touches

✅ Passed checks (3 passed)

Check name	Status	Explanation
Title Check	✅ Passed	The title succinctly describes the primary change—adding support for the longform v-slot:fallback syntax in the <DevOnly> component—using a conventional commit format and clear language, which makes understanding the main change straightforward for reviewers.
Description Check	✅ Passed	The pull request description clearly states the modification by contrasting the previous shorthand-only support with the newly added longform syntax support, which directly aligns with the changes in the code.
Docstring Coverage	✅ Passed	No functions found in the changes. Docstring coverage check skipped.

✨ Finishing touches

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• Commit unit tests in branch fix/dev-only-longform-slot

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📜 Recent review details

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📥 Commits

Reviewing files that changed from the base of the PR and between be9706d and fd9ab8f.

📒 Files selected for processing (1)

• packages/nuxt/src/core/plugins/dev-only.ts (1 hunks)

🧰 Additional context used

📓 Path-based instructions (1)

**/*.{ts,tsx}

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Follow standard TypeScript conventions and best practices

Files:

• packages/nuxt/src/core/plugins/dev-only.ts

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🔇 Additional comments (2)

packages/nuxt/src/core/plugins/dev-only.ts (2)

31-31: LGTM! Longform slot syntax support added correctly.

The addition of 'v-slot:fallback' extends the attribute detection to support Vue's longform slot syntax whilst maintaining backward compatibility with the existing 'fallback' and '#fallback' syntaxes.

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33-33: .at() usage is safe under ES2022 target
The project’s tsconfig sets both target and lib to ES2022, which natively supports Array.prototype.at. No further changes required.

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@nuxt/kit

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commit: fd9ab8f

[codspeed-hq]

CodSpeed Performance Report

Merging #33368 will not alter performance

_{Comparing fix/dev-only-longform-slot (fd9ab8f) with main (be9706d)}

Summary

✅ 10 untouched