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fix(pullAt): fix incorrect element removal with negative indices #1613

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fix(pullAt): fix incorrect element removal with negative indices #1613

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d3c02ea
fix(pullAt): resolve incorrect element removal with negative indices
eunwoo-levi Feb 11, 2026
9c01574
Merge branch 'main' into fix/pullAt-negative-indices
eunwoo-levi Mar 22, 2026
1432c70
Merge branch 'main' into fix/pullAt-negative-indices
eunwoo-levi Apr 10, 2026
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24 changes: 24 additions & 0 deletions src/array/pullAt.spec.ts
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Original file line number Diff line number Diff line change
Expand Up @@ -50,6 +50,30 @@ describe('pullAt', () => {
expect(actual).toEqual([2, 4, 12, 8, 6, 10]);
});

it('should work with a single negative index', () => {
const array = [10, 20, 30, 40, 50];
const result = pullAt(array, [-1]);

expect(array).toEqual([10, 20, 30, 40]);
expect(result).toEqual([50]);
});

it('should work with multiple negative indices', () => {
const array = [10, 20, 30, 40, 50];
const result = pullAt(array, [-1, -2]);

expect(array).toEqual([10, 20, 30]);
expect(result).toEqual([50, 40]);
});
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Copilot AI Feb 11, 2026

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The new negative-index tests cover in-range negatives, but there’s still no coverage for out-of-range negatives (e.g. index < -array.length). Given at() returns undefined for those, it would be good to add a case asserting pullAt also returns undefined and does not remove any element for such indices.

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it('should work with mixed positive and negative indices', () => {
const array = [10, 20, 30, 40, 50];
const result = pullAt(array, [0, -1]);

expect(array).toEqual([20, 30, 40]);
expect(result).toEqual([10, 50]);
});

it('should work with objects', () => {
const foo = { foo: 1 };
const bar = { foo: 2 };
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4 changes: 3 additions & 1 deletion src/array/pullAt.ts
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Expand Up @@ -18,7 +18,9 @@ import { at } from './at.ts';
*/
export function pullAt<T>(arr: T[], indicesToRemove: number[]): T[] {
const removed = at(arr, indicesToRemove);
const indices = new Set(indicesToRemove.slice().sort((x, y) => y - x));

const normalizedIndices = indicesToRemove.map(index => (index < 0 ? arr.length + index : index));
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Copilot AI Feb 11, 2026

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normalizedIndices only adds arr.length for negative values, but doesn’t apply the same integer coercion / bounds handling as at(). This can cause pullAt to mutate the array for out-of-range negative indices (e.g. index < -arr.length becomes a negative normalized index and splice will remove from the end) even though at() returns undefined for those keys. Consider normalizing indices using the same rules as at() (truncate non-integers, add length for negatives) and then filtering out indices that are still out of [0, length) before splicing, so nonexistent indices don’t remove unrelated elements.

Suggested change
const normalizedIndices = indicesToRemove.map(index => (index < 0 ? arr.length + index : index));
const length = arr.length;
const normalizedIndices = indicesToRemove
.map((index) => {
let idx = Math.trunc(index);
if (idx < 0) idx += length;
return idx;
})
.filter((idx) => idx >= 0 && idx < length);

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const indices = new Set(normalizedIndices.slice().sort((x, y) => y - x));

for (const index of indices) {
arr.splice(index, 1);
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