snippets: fix disambiguation of completions with identical prefixes

[xingsy97]

Problem

SnippetCompletionProvider._disambiguateSnippets() sorts completions and then compares adjacent labels to detect duplicates. The comparison uses item.label === suggestions[to].label, but label is a CompletionItemLabel object ({ label: string, description: string }), not a string. Since each SnippetCompletion creates a fresh object in its constructor, === always returns false (reference equality), and the disambiguation suffix is never appended.

When multiple snippets share the same prefix (e.g. two 'for' snippets from different sources), they appear with identical labels in the completion list with no way to distinguish them.

Fix

Compare the label.label string property instead of the label object reference.

[Copilot]

Pull request overview

Fixes snippet completion disambiguation when multiple snippet completions share the same prefix by comparing the underlying label string (CompletionItemLabel.label) instead of the label object reference, so duplicates can be detected and renamed.

Changes:

• Update duplicate-detection logic in _disambiguateSnippets() to compare item.label.label strings instead of item.label object identity.

Comments suppressed due to low confidence (1)

src/vs/workbench/contrib/snippets/browser/snippetCompletionProvider.ts:196

• Now that duplicate snippet prefixes are actually detected, the if (to > i + 1) branch will run; however the subsequent i = to (next line) causes the outer for loop to skip the first non-duplicate entry after a run. This can miss disambiguation for a following duplicate group (e.g. labels a,a,b,b would never disambiguate b). Set the index so the next iteration starts at to (commonly by assigning i = to - 1 before the loop increment), or refactor to a while loop to avoid off-by-one issues.

			for (; to < suggestions.length && item.label.label === suggestions[to].label.label; to++) {
				suggestions[to].label.label = localize('snippetSuggest.longLabel', "{0}, {1}", suggestions[to].label.label, suggestions[to].snippet.name);
			}
			if (to > i + 1) {
				suggestions[i].label.label = localize('snippetSuggest.longLabel', "{0}, {1}", suggestions[i].label.label, suggestions[i].snippet.name);

[Copilot]

This change fixes duplicate-prefix detection, but there doesn't appear to be test coverage asserting that multiple snippets with the same prefix get disambiguated (e.g. label becomes ", "). Consider adding a unit test in the existing snippetsService test suite that registers two snippets with the same prefix and asserts the resulting completion labels are distinct.