Fix declaration-property-value-no-unknown performance

.changeset/light-keys-deny.md

@@ -0,0 +1,5 @@
+---
+"stylelint": patch
+---
+
+Fixed: `declaration-property-value-no-unknown` performance

lib/rules/declaration-property-value-no-unknown/index.mjs

@@ -39,6 +39,10 @@ const SYNTAX_DESCRIPTOR = /^syntax$/i;
 
 const UNSUPPORTED_FUNCTIONS_IN_CSSTREE = new Set(['clamp', 'min', 'max', 'env']);
 
+/** @type {WeakMap<object, Set<string>>} */
+const validMatchesCacheByLexer = new WeakMap();
+const MAX_CACHE_SIZE = 10000;
+
 /** @import { CssNode } from 'css-tree' */
 /** @import { ParseError } from '@csstools/css-calc' */
 
@@ -126,6 +130,13 @@ const rule = (primary, secondaryOptions) => {
 				})
 			: result.stylelint.lexer;
 
+		let validMatchesCache = validMatchesCacheByLexer.get(lexer);
+
+		if (!validMatchesCache) {
+			validMatchesCache = new Set();
+			validMatchesCacheByLexer.set(lexer, validMatchesCache);
+		}
+
 		root.walkDecls((decl) => {
 			const { prop } = decl;
 			const value = getDeclarationValue(decl);
@@ -151,11 +162,19 @@ const rule = (primary, secondaryOptions) => {
 			// skipping parsing by returning early until this is resolved upstream.
 			if (/\bvar\s*\(/i.test(value)) return;
 
+			const cacheKey = isCustomProperty(prop) ? null : `${prop}:${value}`;
+
+			if (cacheKey && validMatchesCache.has(cacheKey)) return;
+
 			// Check if value contains math functions that need validation
 			const [mathFuncResult, mathFuncResultStartOffset, mathFuncResultEndOffset] =
 				validateMathFunctions(value, prop, lexer, typedCustomPropertyNames);
 
-			if (mathFuncResult === 'valid' || mathFuncResult === 'skip-validation') return;
+			if (mathFuncResult === 'valid' || mathFuncResult === 'skip-validation') {
+				if (cacheKey && validMatchesCache.size < MAX_CACHE_SIZE) validMatchesCache.add(cacheKey);
+
+				return;
+			}
 
 			if (mathFuncResult === 'invalid') {
 				const valueIndex = declarationValueIndex(decl);
@@ -217,7 +236,11 @@ const rule = (primary, secondaryOptions) => {
 				cssTreeValueNode,
 			);
 
-			if (!error) return;
+			if (!error) {
+				if (cacheKey && validMatchesCache.size < MAX_CACHE_SIZE) validMatchesCache.add(cacheKey);
+
+				return;
+			}
 
 			if (!('mismatchLength' in error)) return;