From c9dde4c49f43065a5c7e1d23f02623261f862b2a Mon Sep 17 00:00:00 2001
From: "Jordan Bolton (jobolton)" <jobolton@microsoft.com>
Date: Mon, 30 Mar 2026 09:43:21 -0500
Subject: [PATCH] Cache knownIdentifiers per scope in
 validateUnknownIdentifiers

Hoist library key computation out of the per-identifier loop and cache
the combined known-identifier list per NodeScope instance. Avoids
repeated array allocation and spreading when multiple unknown identifiers
share the same scope.

Co-authored-by: Copilot <223556219+Copilot@users.noreply.github.com>
---
 package-lock.json                              |  4 ++--
 package.json                                   |  2 +-
 .../validate/validateUnknownIdentifiers.ts     | 18 ++++++++++++++----
 3 files changed, 17 insertions(+), 7 deletions(-)

diff --git a/package-lock.json b/package-lock.json
index dbe1031b..7908a48a 100644
--- a/package-lock.json
+++ b/package-lock.json
@@ -1,12 +1,12 @@
 {
     "name": "@microsoft/powerquery-language-services",
-    "version": "0.14.0",
+    "version": "0.14.1",
     "lockfileVersion": 3,
     "requires": true,
     "packages": {
         "": {
             "name": "@microsoft/powerquery-language-services",
-            "version": "0.14.0",
+            "version": "0.14.1",
             "license": "MIT",
             "dependencies": {
                 "@microsoft/powerquery-formatter": "0.3.20",
diff --git a/package.json b/package.json
index a44f755c..0d0c8d97 100644
--- a/package.json
+++ b/package.json
@@ -1,6 +1,6 @@
 {
     "name": "@microsoft/powerquery-language-services",
-    "version": "0.14.0",
+    "version": "0.14.1",
     "author": "Microsoft",
     "license": "MIT",
     "scripts": {
diff --git a/src/powerquery-language-services/validate/validateUnknownIdentifiers.ts b/src/powerquery-language-services/validate/validateUnknownIdentifiers.ts
index b02acb8a..584fdf5b 100644
--- a/src/powerquery-language-services/validate/validateUnknownIdentifiers.ts
+++ b/src/powerquery-language-services/validate/validateUnknownIdentifiers.ts
@@ -129,6 +129,14 @@ function findUnknownIdentifiers(
 
     const unknownIdentifiers: UnknownIdentifier[] = [];
 
+    // Compute library keys once for the entire validation run instead of per-unknown-identifier.
+    const libraryKeys: ReadonlyArray<string> = LibraryUtils.getDefinitionKeys(validationSettings.library);
+
+    // Cache the combined known-identifier list per NodeScope instance.
+    // Multiple identifiers in the same scope (e.g. bindings in a let) share the same list,
+    // avoiding repeated array allocation and spreading.
+    const knownIdentifiersByScope: Map<Inspection.NodeScope, ReadonlyArray<string>> = new Map();
+
     for (const identifierWithNodeScope of identifiersWithNodeScope) {
         if (ResultUtils.isError(identifierWithNodeScope.triedNodeScope)) {
             continue;
@@ -146,10 +154,12 @@ function findUnknownIdentifiers(
                 identifierLiteral: literal,
             })
         ) {
-            const knownIdentifiers: ReadonlyArray<string> = [
-                ...nodeScope.scopeItemByKey.keys(),
-                ...LibraryUtils.getDefinitionKeys(validationSettings.library),
-            ];
+            let knownIdentifiers: ReadonlyArray<string> | undefined = knownIdentifiersByScope.get(nodeScope);
+
+            if (knownIdentifiers === undefined) {
+                knownIdentifiers = [...nodeScope.scopeItemByKey.keys(), ...libraryKeys];
+                knownIdentifiersByScope.set(nodeScope, knownIdentifiers);
+            }
 
             const [jaroWinklerScore, suggestion]: [number, string] = calculateJaroWinklers(literal, knownIdentifiers);