fix(arrays): clean up duplicate logic and improve array helpers

[mohityadav8]

Summary

This PR improves several utilities in src/vs/base/common/arrays.ts:

• removes redundant assignment logic in range()
• updates withoutDuplicates() to reuse distinct() instead of duplicating logic, while preserving API compatibility
• replaces [].concat(...arrays) in concatArrays() with an iterative implementation to avoid spread argument limits and improve type safety

Testing

• Verified the diff only affects the intended three utility functions in arrays.ts
• No public API was removed

Notes

I intentionally did not remove deprecated exports (move, insert, remove) since that would be a breaking API change and is better handled separately.

[Copilot]

Pull request overview

This PR refactors a few core utilities in src/vs/base/common/arrays.ts to reduce duplicated logic and adjust array helper implementations within the vs/base/common layer.

Changes:

• Reworked concatArrays() to build results iteratively instead of using [].concat(...arrays).
• Simplified range() initialization logic.
• Updated withoutDuplicates() to delegate to distinct().

Comments suppressed due to low confidence (1)

src/vs/base/common/arrays.ts:594

• withoutDuplicates previously preserved sparse-array holes as undefined (via new Set(array) / array iteration). Switching to distinct(array) changes behavior because distinct uses array.filter(...), which skips holes entirely. If API compatibility for sparse arrays matters, consider keeping the old Set-based implementation here or updating distinct/this wrapper to iterate with for...of instead of filter.

export function asArray<T>(x: T | T[]): T[];
export function asArray<T>(x: T | readonly T[]): readonly T[];

[mohityadav8]

@microsoft-github-policy-service agree

[Copilot]

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Comments suppressed due to low confidence (1)

src/vs/base/common/arrays.ts:593

• withoutDuplicates used to be Array.from(new Set(array)), which visits array holes via the iterator (treating them as undefined). distinct(array) uses filter, which skips holes entirely, so sparse arrays will now lose the hole/undefined entry and this is a behavior change despite the same signature. If you want to keep the previous semantics while reusing distinct, consider calling distinct(Array.from(array)) (or keep the original Set-based implementation).

export function withoutDuplicates<T>(array: ReadonlyArray<T>): T[] {
	return distinct(array);
}

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Comments suppressed due to low confidence (1)

src/vs/base/common/arrays.ts:213

• The manual copy loop in concatArrays does not preserve sparse array holes: reading arr[i] and assigning to result[...] will materialize holes as explicit undefined entries, whereas Array.prototype.concat preserves holes. If callers rely on hole semantics (e.g. i in array checks), consider copying only existing indices (e.g. if (i in arr)) and setting result.length = offset + arr.length to keep holes.

	for (const arr of arrays) {
		const offset = result.length;
		for (let i = 0; i < arr.length; i++) {
			result[offset + i] = arr[i];
		}
	}

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[mohityadav8]

cc @mjbvz :D

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Copilot reviewed 1 out of 1 changed files in this pull request and generated 3 comments.