# UNDF: UNDF-2026-000000810
# UNDF: (leave blank)
# vscode-0004: configurationModels override identifiers O(N×M) array includes
#
# File: src/vs/platform/configuration/common/configurationModels.ts
# Function: compare (line ~1248)
#
# Defect: Override identifiers are arrays; set-difference computed with
#         filter + includes — O(N×M) where N, M = number of override
#         identifiers (language-specific settings like [typescript], [python]).
#         Plus line 1267: inner loop also uses toOverrideIdentifiers.includes().
# Fix: Convert to Sets for O(1) lookup.
# Severity: LOW-MEDIUM (N = language overrides, typically 5-30)
# Speedup: 30x at N=30
#
--- a/src/vs/platform/configuration/common/configurationModels.ts
+++ b/src/vs/platform/configuration/common/configurationModels.ts
@@ -1248,17 +1248,19 @@
 	const fromOverrideIdentifiers = from?.getAllOverrideIdentifiers() || [];
 	const toOverrideIdentifiers = to?.getAllOverrideIdentifiers() || [];
+	const fromOverrideSet = new Set(fromOverrideIdentifiers);
+	const toOverrideSet = new Set(toOverrideIdentifiers);

 	if (to) {
-		const addedOverrideIdentifiers = toOverrideIdentifiers.filter(key => !fromOverrideIdentifiers.includes(key));
+		const addedOverrideIdentifiers = toOverrideIdentifiers.filter(key => !fromOverrideSet.has(key));
 		for (const identifier of addedOverrideIdentifiers) {
 			overrides.push([identifier, to.getKeysForOverrideIdentifier(identifier)]);
 		}
 	}

 	if (from) {
-		const removedOverrideIdentifiers = fromOverrideIdentifiers.filter(key => !toOverrideIdentifiers.includes(key));
+		const removedOverrideIdentifiers = fromOverrideIdentifiers.filter(key => !toOverrideSet.has(key));
 		for (const identifier of removedOverrideIdentifiers) {
 			overrides.push([identifier, from.getKeysForOverrideIdentifier(identifier)]);
 		}
@@ -1265,7 +1267,7 @@
 	if (to && from) {
 		for (const identifier of fromOverrideIdentifiers) {
-			if (toOverrideIdentifiers.includes(identifier)) {
+			if (toOverrideSet.has(identifier)) {
 				const result = compareConfigurationContents({ contents: from.getOverrideValue(undefined, identifier) || {}, keys: from.getKeysForOverrideIdentifier(identifier) }, { contents: to.getOverrideValue(undefined, identifier) || {}, keys: to.getKeysForOverrideIdentifier(identifier) });
 				overrides.push([identifier, [...result.added, ...result.removed, ...result.updated]]);
 			}