fix(CommandPalette): keep astral characters intact when truncating search results

[arsalan507]

🔗 Linked issue

None open — filing this directly as it's a small, self-contained bug.

❓ Type of change

• 🐞 Bug fix (a non-breaking change that fixes an issue)

📚 Description

truncateHTMLFromStart in src/runtime/utils/search.ts walks the highlighted snippet in reverse one UTF-16 code unit at a time (html[i]). An astral character — emoji, most CJK extension blocks, many symbols — occupies two code units. When the truncation boundary lands between them, the surrogate pair is sliced in half and the output carries an unpaired surrogate, which renders as �.

This is user-visible in CommandPalette and useContentSearch, where indexed content is more likely to contain emoji than a hand-written command label: a search result whose match sits after an emoji gets a � at the truncation point.

Reproduction — sweeping filler lengths 1–40 of 😀 before the match, lone surrogates appear from filler length 7 onward and for every length after:

n=10, before: "...\uDE00😀😀😀😀😀😀<mark>match</mark>"
n=10, after:  "😀😀😀😀😀😀😀😀😀😀<mark>match</mark>"

Not a security issue. A lone surrogate can only render as a broken glyph or U+FFFD — it cannot manufacture HTML syntax, and no raw <, >, &, " or ' appears outside the <mark> tags the highlighter inserts itself. This is a correctness and appearance bug.

🔧 The fix

Two hunks:

1. truncateHTMLFromStart — iterate with Array.from(html) so a surrogate pair is never split. The insideTag logic is untouched, since < and > are always single code units.
2. The caller — measure the length budget in code points too, so it stays in the same units as the counter inside the function.

Worth calling out explicitly for review: hunk 2 is a consistency fix, not required to remove the lone surrogates — hunk 1 alone is sufficient. It does mean an emoji now counts as one character against the truncation budget rather than two, so emoji-containing snippets truncate slightly later than before. That seems closer to the intent of a visible-length budget, but happy to drop hunk 2 if you'd rather keep the diff minimal.

Behaviour for BMP-only content is byte-identical, which is why all pre-existing tests pass untouched.

✅ Verification

Added three tests to test/utils/search.spec.ts:

• never splits an astral character, at any truncation boundary — the 1–40 sweep, asserting no lone surrogate at any length
• keeps emoji before the match intact
• still truncates a long prefix down to an ellipsis — guards against over-correcting into "never truncate"

Verified the first two fail against unmodified search.ts (expected [ 7, 8, 9, … ] to deeply equal []) and pass with the fix. The third passes both before and after by design.

test/utils/search.spec.ts            13 passed   (10 pre-existing, 3 new)
test/utils/ (both projects)         138 passed
CommandPalette + DashboardSearch +
ChatPalette + DashboardSearchButton 146 passed
eslint src/runtime/utils/search.ts test/utils/search.spec.ts   clean

📝 Checklist

• I have linked an issue or discussion (n/a — none open)
• I have added tests (if applicable)

[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: 0093958a-a748-495a-ac3d-89bf03d5bcbf

📥 Commits

Reviewing files that changed from the base of the PR and between 6add5fb and 16016db.

📒 Files selected for processing (2)

• src/runtime/utils/search.ts
• test/utils/search.spec.ts

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📝 Walkthrough

Walkthrough

HTML truncation now iterates over Unicode code points instead of UTF-16 code units. Highlight truncation budgets also use code-point counts. New tests verify that emoji and other astral characters remain intact, long prefixes receive an ellipsis, and highlighted matches remain present.

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

🚥 Pre-merge checks | ✅ 5

✅ Passed checks (5 passed)

Check name	Status	Explanation
Description check	✅ Passed	The description clearly explains the astral-character truncation bug, the fix, added tests, and verification results.
Title check	✅ Passed	The title clearly and concisely identifies the fix for preserving astral characters during search-result truncation.
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 unit tests (beta)

• Create PR with unit tests

Warning

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🔧 ESLint

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src/runtime/utils/search.ts

Parsing error: Unexpected token {

test/utils/search.spec.ts

Parsing error: Unexpected token :

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[pkg-pr-new]

npm i https://pkg.pr.new/@nuxt/ui@6817

commit: 6e97151

[codspeed-hq]

Merging this PR will not alter performance

✅ 31 untouched benchmarks

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_{Comparing arsalan507:fix/search-truncate-astral-characters (6e97151) with v4 (6add5fb)}