fix(theme): blank top-level base in applyUnstyled

[benjamincanac]

🔗 Linked issue

Relates to #6551

❓ Type of change

• 📖 Documentation (updates to the documentation or readme)
• 🐞 Bug fix (a non-breaking change that fixes an issue)
• 👌 Enhancement (improving an existing functionality)
• ✨ New feature (a non-breaking change that adds functionality)
• 🧹 Chore (updates to the build process or auxiliary tools and libraries)
• ⚠️ Breaking change (fix or feature that would cause existing functionality to change)

📚 Description

applyUnstyled only blanks slots, variants and compoundVariants. Themes come in two shapes: multi-element components put their classes under slots, single-element ones are a top-level base string (or array). There's no base branch, so with theme.unstyled enabled the 37 base-shaped themes (skeleton, kbd, container, main, the prose elements, ...) come out identical to the original and keep every class, while everything slots-shaped is blanked. The docs promise the option removes the default classes from all components at once, so this is a plain hole.

While in there, applyUnstyled no longer mutates the theme it receives: object-shaped themes are the shared module export (function-shaped ones produce a fresh object per call), so blanking in place corrupts every later read within the same process.

Covered by unit tests for both fixes. #6731 blanks unused component themes through this same function, so it picks this up on its next v4 merge.

📝 Checklist

• I have linked an issue or discussion.
• I have updated the documentation accordingly.

[coderabbitai]

No actionable comments were generated in the recent review. 🎉

ℹ️ Recent review info

⚙️ Run configuration

Configuration used: Organization UI

Review profile: CHILL

Plan: Pro Plus

Run ID: da72ec40-4645-449b-a3bc-fb8d6fc12d79

📥 Commits

Reviewing files that changed from the base of the PR and between 80cad10 and b385796.

📒 Files selected for processing (2)

• src/utils/theme.ts
• test/utils/theme.spec.ts

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📝 Walkthrough

Walkthrough

applyUnstyled now shallow-copies theme results before applying blanking changes. It clears top-level base classes for single-element components. Tests cover string and array base values and verify that object-shaped themes are not mutated.

Estimated code review effort: 2 (Simple) | ~10 minutes

🚥 Pre-merge checks | ✅ 5

✅ Passed checks (5 passed)

Check name	Status	Explanation
Title check	✅ Passed	The title clearly identifies the primary fix: blanking top-level base values in applyUnstyled.
Description check	✅ Passed	The description directly explains both fixes and identifies the related tests and issue.
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.

✨ Finishing Touches

📝 Generate docstrings

• Create stacked PR
• Commit on current branch

🧪 Generate unit tests (beta)

• Create PR with unit tests
• Commit unit tests in branch fix/unstyled-base

Warning

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🔧 ESLint

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src/utils/theme.ts

Parsing error: Unexpected token :

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[codspeed-hq]

Merging this PR will not alter performance

✅ 31 untouched benchmarks

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_{Comparing fix/unstyled-base (b385796) with v4 (80cad10)}

[pkg-pr-new]

npm i https://pkg.pr.new/@nuxt/ui@6825

commit: b385796