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Add LRU cache for CSS parsing and validation #271

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7661cf8
Add LRU cache utility module
asamuzaK Dec 27, 2025
e7b1e52
Add caching to property value parsing functions
asamuzaK Dec 27, 2025
33d1e13
Sort exports
asamuzaK Dec 27, 2025
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234 changes: 136 additions & 98 deletions lib/parsers.js
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Original file line number Diff line number Diff line change
Expand Up @@ -6,6 +6,7 @@ const {
} = require("@asamuzakjp/css-color");
const { next: syntaxes } = require("@csstools/css-syntax-patches-for-csstree");
const csstree = require("css-tree");
const { getCache, setCache } = require("./utils/cache");
const { asciiLowercase } = require("./utils/strings");

// CSS global keywords
Expand Down Expand Up @@ -193,16 +194,25 @@ const isValidPropertyValue = (prop, val) => {
}
return false;
}
let ast;
const cacheKey = `isValidPropertyValue_${prop}_${val}`;
const cachedValue = getCache(cacheKey);
if (typeof cachedValue === "boolean") {
return cachedValue;
}
let result;
try {
ast = parseCSS(val, {
context: "value"
const ast = parseCSS(val, {
options: {
context: "value"
}
});
const { error, matched } = cssTree.lexer.matchProperty(prop, ast);
result = error === null && matched !== null;
} catch {
return false;
result = false;
}
const { error, matched } = cssTree.lexer.matchProperty(prop, ast);
return error === null && matched !== null;
setCache(cacheKey, result);
return result;
};

/**
Expand All @@ -219,6 +229,11 @@ const resolveCalc = (val, opt = { format: "specifiedValue" }) => {
if (val === "" || hasVarFunc(val) || !hasCalcFunc(val)) {
return val;
}
const cacheKey = `resolveCalc_${val}`;
const cachedValue = getCache(cacheKey);
if (typeof cachedValue === "string") {
return cachedValue;
}
const obj = parseCSS(val, { context: "value" }, true);
if (!obj?.children) {
return;
Expand All @@ -244,7 +259,9 @@ const resolveCalc = (val, opt = { format: "specifiedValue" }) => {
values.push(itemName ?? itemValue);
}
}
return values.join(" ");
const resolvedValue = values.join(" ");
setCache(cacheKey, resolvedValue);
return resolvedValue;
};

/**
Expand All @@ -270,123 +287,144 @@ const parsePropertyValue = (prop, val, opt = {}) => {
}
val = calculatedValue;
}
const cacheKey = `parsePropertyValue_${prop}_${val}_${caseSensitive}`;
const cachedValue = getCache(cacheKey);
if (cachedValue === false) {
return;
} else if (inArray) {
if (Array.isArray(cachedValue)) {
return cachedValue;
}
} else if (typeof cachedValue === "string") {
return cachedValue;
}
let parsedValue;
const lowerCasedValue = asciiLowercase(val);
if (GLOBAL_KEYS.has(lowerCasedValue)) {
if (inArray) {
return [
parsedValue = [
{
type: AST_TYPES.GLOBAL_KEYWORD,
name: lowerCasedValue
}
];
} else {
parsedValue = lowerCasedValue;
}
return lowerCasedValue;
} else if (SYS_COLORS.has(lowerCasedValue)) {
if (/^(?:(?:-webkit-)?(?:[a-z][a-z\d]*-)*color|border)$/i.test(prop)) {
if (inArray) {
return [
parsedValue = [
{
type: AST_TYPES.IDENTIFIER,
name: lowerCasedValue
}
];
} else {
parsedValue = lowerCasedValue;
}
return lowerCasedValue;
}
return;
}
try {
const ast = parseCSS(val, {
context: "value"
});
const { error, matched } = cssTree.lexer.matchProperty(prop, ast);
if (error || !matched) {
return;
} else {
parsedValue = false;
}
if (inArray) {
const obj = cssTree.toPlainObject(ast);
const items = obj.children;
const parsedValues = [];
for (const item of items) {
const { children, name, type, value, unit } = item;
switch (type) {
case AST_TYPES.DIMENSION: {
parsedValues.push({
type,
value,
unit: asciiLowercase(unit)
});
break;
}
case AST_TYPES.FUNCTION: {
const css = cssTree
.generate(item)
.replace(/\)(?!\)|\s|,)/g, ") ")
.trim();
const raw = items.length === 1 ? val : css;
// Remove "${name}(" from the start and ")" from the end
const itemValue = raw.slice(name.length + 1, -1).trim();
if (name === "calc") {
if (children.length === 1) {
const [child] = children;
if (child.type === AST_TYPES.NUMBER) {
parsedValues.push({
type: AST_TYPES.CALC,
isNumber: true,
value: `${parseFloat(child.value)}`,
name,
raw
});
} else {
try {
const ast = parseCSS(val, {
context: "value"
});
const { error, matched } = cssTree.lexer.matchProperty(prop, ast);
if (error || !matched) {
parsedValue = false;
} else if (inArray) {
const obj = cssTree.toPlainObject(ast);
const items = obj.children;
const values = [];
for (const item of items) {
const { children, name, type, value, unit } = item;
switch (type) {
case AST_TYPES.DIMENSION: {
values.push({
type,
value,
unit: asciiLowercase(unit)
});
break;
}
case AST_TYPES.FUNCTION: {
const css = cssTree
.generate(item)
.replace(/\)(?!\)|\s|,)/g, ") ")
.trim();
const raw = items.length === 1 ? val : css;
// Remove "${name}(" from the start and ")" from the end
const itemValue = raw.slice(name.length + 1, -1).trim();
if (name === "calc") {
if (children.length === 1) {
const [child] = children;
if (child.type === AST_TYPES.NUMBER) {
values.push({
type: AST_TYPES.CALC,
isNumber: true,
value: `${parseFloat(child.value)}`,
name,
raw
});
} else {
values.push({
type: AST_TYPES.CALC,
isNumber: false,
value: `${asciiLowercase(itemValue)}`,
name,
raw
});
}
} else {
parsedValues.push({
values.push({
type: AST_TYPES.CALC,
isNumber: false,
value: `${asciiLowercase(itemValue)}`,
value: asciiLowercase(itemValue),
name,
raw
});
}
} else {
parsedValues.push({
type: AST_TYPES.CALC,
isNumber: false,
value: asciiLowercase(itemValue),
values.push({
type,
name,
value: asciiLowercase(itemValue),
raw
});
}
} else {
parsedValues.push({
type,
name,
value: asciiLowercase(itemValue),
raw
});
break;
}
break;
}
case AST_TYPES.IDENTIFIER: {
if (caseSensitive) {
parsedValues.push(item);
} else {
parsedValues.push({
type,
name: asciiLowercase(name)
});
case AST_TYPES.IDENTIFIER: {
if (caseSensitive) {
values.push(item);
} else {
values.push({
type,
name: asciiLowercase(name)
});
}
break;
}
default: {
values.push(item);
}
break;
}
default: {
parsedValues.push(item);
}
}
parsedValue = values;
} else {
parsedValue = val;
}
return parsedValues;
} catch {
parsedValue = false;
}
} catch {
}
setCache(cacheKey, parsedValue);
if (parsedValue === false) {
return;
}
return val;
return parsedValue;
};

/**
Expand Down Expand Up @@ -639,22 +677,22 @@ const parseGradient = (val) => {
};

module.exports = {
prepareValue,
isGlobalKeyword,
hasVarFunc,
hasCalcFunc,
splitValue,
parseCSS,
hasVarFunc,
isGlobalKeyword,
isValidPropertyValue,
resolveCalc,
parsePropertyValue,
parseNumber,
parseAngle,
parseCSS,
parseColor,
parseGradient,
parseLength,
parsePercentage,
parseLengthPercentage,
parseAngle,
parseUrl,
parseNumber,
parsePercentage,
parsePropertyValue,
parseString,
parseColor,
parseGradient
parseUrl,
prepareValue,
resolveCalc,
splitValue
};
40 changes: 40 additions & 0 deletions lib/utils/cache.js
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Original file line number Diff line number Diff line change
@@ -0,0 +1,40 @@
"use strict";

const { LRUCache } = require("lru-cache");

// Instance of the LRU Cache. Stores up to 4096 items.
const lruCache = new LRUCache({
max: 4096
});

// A sentinel symbol used to store null values, as lru-cache does not support nulls.
const nullSentinel = Symbol("null");

/**
* Sets a value in the cache for the given key.
* If the value is null, it is internally stored as `nullSentinel`.
*
* @param {string|number} key - The cache key.
* @param {any} value - The value to be cached.
* @returns {void}
*/
const setCache = (key, value) => {
lruCache.set(key, value === null ? nullSentinel : value);
};

/**
* Retrieves the cached value associated with the given key.
* If the stored value is `nullSentinel`, it returns null.
*
* @param {string|number} key - The cache key.
* @returns {any|null|undefined} The cached item, undefined if the key does not exist.
*/
const getCache = (key) => {
const value = lruCache.get(key);
return value === nullSentinel ? null : value;
};

module.exports = {
getCache,
setCache
};
3 changes: 2 additions & 1 deletion package-lock.json
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3 changes: 2 additions & 1 deletion package.json
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Original file line number Diff line number Diff line change
Expand Up @@ -18,7 +18,8 @@
"dependencies": {
"@asamuzakjp/css-color": "^4.1.1",
"@csstools/css-syntax-patches-for-csstree": "^1.0.21",
"css-tree": "^3.1.0"
"css-tree": "^3.1.0",
"lru-cache": "^11.2.4"
},
"devDependencies": {
"@babel/generator": "^7.28.5",
Expand Down