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fix: keep position: 'middle' within the column budget #32

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Merged
sindresorhus merged 2 commits into from
Jun 23, 2026
+26 −3
Merged

fix: keep position: 'middle' within the column budget #32

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af082f7
fix: keep `position: 'middle'` within the column budget
spokodev Jun 22, 2026
7969457
fix: reserve the truncation width in the prefer-on-space middle branch
spokodev Jun 23, 2026
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16 changes: 13 additions & 3 deletions index.js
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Original file line number Diff line number Diff line change
Expand Up @@ -132,20 +132,30 @@ export default function cliTruncate(text, columns, options = {}) {
if (position === 'middle') {
if (space) {
truncationCharacter = ` ${truncationCharacter} `;

// Drop the padding spaces if the padded character does not fit, so the
// truncation character itself never exceeds the budget.
if (stringWidth(truncationCharacter) >= columns) {
truncationCharacter = truncationCharacter.trim();
}
}

const half = Math.floor(columns / 2);
const truncationWidth = stringWidth(truncationCharacter);
// Reserve room for the truncation character before splitting the budget
// between the two sides, otherwise small budgets overflow (e.g. a width of
// 4 was returned for `columns: 2`).
const half = Math.min(Math.floor(columns / 2), Math.max(0, columns - truncationWidth));

if (preferTruncationOnSpace) {
const spaceNearFirstBreakPoint = getIndexOfNearestSpace(text, half);
const spaceNearSecondBreakPoint = getIndexOfNearestSpace(text, length - (columns - half) + 1, true);
const spaceNearSecondBreakPoint = getIndexOfNearestSpace(text, length - (columns - half) + truncationWidth, true);
return sliceAnsi(text, 0, spaceNearFirstBreakPoint) + truncationCharacter + sliceAnsi(text, spaceNearSecondBreakPoint, length).trim();
}

return (
sliceAnsi(text, 0, half)
+ truncationCharacter
+ sliceAnsi(text, length - (columns - half) + stringWidth(truncationCharacter), length)
+ sliceAnsi(text, length - (columns - half) + truncationWidth, length)
);
}

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13 changes: 13 additions & 0 deletions test.js
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Original file line number Diff line number Diff line change
Expand Up @@ -35,6 +35,13 @@ test('space option', t => {
t.is(cliTruncate('\u001B[31municornsareawesome\u001B[39m', 10, {position: 'middle', space: true}), '\u001B[31munico\u001B[39m … \u001B[31mme\u001B[39m');
t.is(cliTruncate('Plant a tree every day.', 14, {position: 'middle', space: true}), 'Plant a … day.');
t.is(cliTruncate('안녕하세요', 4, {position: 'start', space: true}), '… 요', 'wide char');

// `middle` + `space` must stay within the budget for small widths
t.is(cliTruncate('unicorns', 2, {position: 'middle', space: true}), 'u…');
t.is(cliTruncate('unicorns', 3, {position: 'middle', space: true}), 'u…s');
for (const columns of [2, 3, 4, 5, 6, 7]) {
t.true(stringWidth(cliTruncate('unicorns', columns, {position: 'middle', space: true})) <= columns, `width <= ${columns}`);
}
});

test('preferTruncationOnSpace option', t => {
Expand All @@ -44,6 +51,12 @@ test('preferTruncationOnSpace option', t => {
t.is(cliTruncate('unicorns rainbow dragons', 6, {position: 'end', preferTruncationOnSpace: true}), 'unico…');
t.is(cliTruncate('unicorns rainbow dragons', 6, {position: 'middle', preferTruncationOnSpace: true}), 'uni…ns');
t.is(cliTruncate('unicorns partying with dragons', 20, {position: 'middle', preferTruncationOnSpace: true}), 'unicorns…dragons');

// `middle` + `space` + `preferTruncationOnSpace` must stay within the budget
t.is(cliTruncate('unicorns', 4, {position: 'middle', space: true, preferTruncationOnSpace: true}), 'u … ');
for (const columns of [2, 3, 4, 5, 6, 7]) {
t.true(stringWidth(cliTruncate('unicorns', columns, {position: 'middle', space: true, preferTruncationOnSpace: true})) <= columns, `width <= ${columns}`);
}
});

test('truncationCharacter option', t => {
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