fix(cli): avoid splitting emoji when truncating display strings

[feizhuzheng]

Summary

sanitizeForDisplay truncates with str.length and str.substring, which count UTF-16 code units. When maxLength falls inside a surrogate pair (an emoji or other astral character), the pair is split and the leftover lone surrogate renders as a replacement character. This affects terminal notification titles/bodies and slash-command descriptions, which can contain emoji.

Details

The same file already exports cpLen and cpSlice, which operate on code points. sanitizeForDisplay now uses them, so length checks and truncation happen on code-point boundaries and a trailing emoji is either kept whole or dropped, never cut in half.

For a purely ASCII string the behavior is unchanged (cpLen/cpSlice short-circuit on the ASCII fast path).

How to Validate

sanitizeForDisplay('🎉'.repeat(10), 8)
// before: "🎉🎉\uD83C..."  (lone surrogate -> renders as )
// after:  "🎉🎉🎉🎉🎉..."

Added a unit test in textUtils.test.ts covering this case (asserts the result contains no lone surrogate) alongside the existing ASCII truncation test.

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[gemini-code-assist]

Summary of Changes

Hello, I'm Gemini Code Assist¹! I'm currently reviewing this pull request and will post my feedback shortly. In the meantime, here's a summary to help you and other reviewers quickly get up to speed!

This pull request addresses an issue where display strings containing emojis or other astral characters were being incorrectly truncated. By switching from UTF-16 code unit-based string operations to code-point-aware utilities, the implementation now ensures that multi-unit characters remain intact during truncation, improving the visual consistency of terminal outputs and command descriptions.

Highlights

• Emoji Truncation Fix: Updated the sanitizeForDisplay function to use code-point-aware length checking and slicing instead of standard string methods.
• Surrogate Pair Integrity: Ensured that astral characters like emojis are not split during truncation, preventing the generation of lone surrogate characters that cause rendering issues.
• Regression Testing: Added a new unit test in textUtils.test.ts to verify that emoji strings are truncated correctly without leaving invalid surrogate pairs.

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[gemini-code-assist]

Code Review

This pull request updates sanitizeForDisplay in textUtils.ts to use code point length (cpLen) and slicing (cpSlice) instead of UTF-16 code unit operations, preventing surrogate pairs (such as emojis) from being split during truncation. A corresponding unit test was also added. The reviewer identified a potential bug where a maxLength of less than 3 would result in a negative end index for cpSlice, which behaves differently than substring and can cause unexpected truncation behavior. A suggestion was provided to use Math.max(0, maxLength - 3) to prevent this issue.

[gemini-code-assist]

Using cpSlice with maxLength - 3 can result in a negative end index if maxLength is less than 3. Unlike String.prototype.substring (which treats negative indices as 0), cpSlice uses slice under the hood, where a negative index is treated as an offset from the end of the string/array. This causes the function to return a much longer string than intended (e.g., slicing all but the last character) and append '...', leading to a bug.

To fix this, we should ensure the end index is at least 0 by using Math.max(0, maxLength - 3).

Suggested change

	if (maxLength && cpLen(sanitized) > maxLength) {
	sanitized = cpSlice(sanitized, 0, maxLength - 3) + '...';
	}
	if (maxLength && cpLen(sanitized) > maxLength) {
	sanitized = cpSlice(sanitized, 0, Math.max(0, maxLength - 3)) + '...';
	}

[github-actions]

📊 PR Size: size/S

• Lines changed: 16
• Additions: +14
• Deletions: -2
• Files changed: 2