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refactor: add cache for template literal parsing #390

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Merged
merged 1 commit into from
Jul 17, 2025
Merged

refactor: add cache for template literal parsing #390

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12 changes: 9 additions & 3 deletions packages/eslint-plugin/lib/rules/indent/indent.js
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Original file line number Diff line number Diff line change
Expand Up @@ -20,7 +20,8 @@
* @property {Record<string, number>} [Option2.tagChildrenIndent]
*/

const { parse } = require("@html-eslint/template-parser");
const { getCachedParseResult } = require("../utils/template-cache");
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An alternative implementation would be to make caching a part of the parse function itself so that this is completely transparent to rules. I opted to go this route to avoid making changes that might be undesirable to anyone who is using the @html-eslint/template-parser package in isolation.

const { traverse } = require("@html-eslint/template-parser/lib/traverser");
const { NODE_TYPES } = require("@html-eslint/parser");
const { RULE_CATEGORY } = require("../../constants");
const {
Expand Down Expand Up @@ -386,13 +387,18 @@ module.exports = {
TaggedTemplateExpression(node) {
if (shouldCheckTaggedTemplateExpression(node, context)) {
const base = getTemplateLiteralBaseIndentLevel(node.quasi);
parse(node.quasi, getSourceCode(context), createIndentVisitor(base));
const { ast } = getCachedParseResult(
node.quasi,
getSourceCode(context)
);
traverse(ast, createIndentVisitor(base), null);
}
},
TemplateLiteral(node) {
if (shouldCheckTemplateLiteral(node, context)) {
const base = getTemplateLiteralBaseIndentLevel(node);
parse(node, getSourceCode(context), createIndentVisitor(base));
const { ast } = getCachedParseResult(node, getSourceCode(context));
traverse(ast, createIndentVisitor(base), null);
}
},
};
Expand Down
28 changes: 21 additions & 7 deletions packages/eslint-plugin/lib/rules/no-duplicate-id.js
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Original file line number Diff line number Diff line change
Expand Up @@ -3,7 +3,8 @@
* @import {RuleModule} from "../types";
*/

const { parse } = require("@html-eslint/template-parser");
const { getCachedParseResult } = require("./utils/template-cache");
const { traverse } = require("@html-eslint/template-parser/lib/traverser");
const { RULE_CATEGORY } = require("../constants");
const { findAttr } = require("./utils/node");
const {
Expand Down Expand Up @@ -90,18 +91,31 @@ module.exports = {
TaggedTemplateExpression(node) {
const idAttrsMap = new Map();
if (shouldCheckTaggedTemplateExpression(node, context)) {
parse(node.quasi, getSourceCode(context), {
Tag: createTagVisitor(idAttrsMap),
});
const { ast } = getCachedParseResult(
node.quasi,
getSourceCode(context)
);
traverse(
ast,
{
Tag: createTagVisitor(idAttrsMap),
},
null
);
}
report(idAttrsMap);
},
TemplateLiteral(node) {
const idAttrsMap = new Map();
if (shouldCheckTemplateLiteral(node, context)) {
parse(node, getSourceCode(context), {
Tag: createTagVisitor(idAttrsMap),
});
const { ast } = getCachedParseResult(node, getSourceCode(context));
traverse(
ast,
{
Tag: createTagVisitor(idAttrsMap),
},
null
);
}
report(idAttrsMap);
},
Expand Down
12 changes: 9 additions & 3 deletions packages/eslint-plugin/lib/rules/no-duplicate-in-head.js
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Original file line number Diff line number Diff line change
Expand Up @@ -3,7 +3,8 @@
* @import {RuleModule} from "../types";
*/

const { parse } = require("@html-eslint/template-parser");
const { getCachedParseResult } = require("./utils/template-cache");
const { traverse } = require("@html-eslint/template-parser/lib/traverser");
const { RULE_CATEGORY } = require("../constants");
const { findAttr } = require("./utils/node");
const {
Expand Down Expand Up @@ -168,7 +169,11 @@ module.exports = {

if (shouldCheckTaggedTemplateExpression(node, context)) {
const visitor = createTagVisitor(tagsMap, headCountRef);
parse(node.quasi, getSourceCode(context), visitor);
const { ast } = getCachedParseResult(
node.quasi,
getSourceCode(context)
);
traverse(ast, visitor, null);
report(tagsMap);
}
},
Expand All @@ -179,7 +184,8 @@ module.exports = {

if (shouldCheckTemplateLiteral(node, context)) {
const visitor = createTagVisitor(tagsMap, headCountRef);
parse(node, getSourceCode(context), visitor);
const { ast } = getCachedParseResult(node, getSourceCode(context));
traverse(ast, visitor, null);
report(tagsMap);
}
},
Expand Down
12 changes: 7 additions & 5 deletions packages/eslint-plugin/lib/rules/no-multiple-empty-lines.js
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Original file line number Diff line number Diff line change
Expand Up @@ -6,7 +6,7 @@
* @property {number} Option.max
*/

const { parse } = require("@html-eslint/template-parser");
const { getCachedParseResult } = require("./utils/template-cache");
const { RULE_CATEGORY } = require("../constants");
const {
shouldCheckTaggedTemplateExpression,
Expand Down Expand Up @@ -117,10 +117,9 @@ module.exports = {
},
TaggedTemplateExpression(node) {
if (shouldCheckTaggedTemplateExpression(node, context)) {
const { html, tokens } = parse(
const { html, tokens } = getCachedParseResult(
node.quasi,
getSourceCode(context),
{}
getSourceCode(context)
);
const lines = codeToLines(html);
check(
Expand All @@ -133,7 +132,10 @@ module.exports = {
},
TemplateLiteral(node) {
if (shouldCheckTemplateLiteral(node, context)) {
const { html, tokens } = parse(node, getSourceCode(context), {});
const { html, tokens } = getCachedParseResult(
node,
getSourceCode(context)
);
const lines = codeToLines(html);
check(
lines,
Expand Down
12 changes: 7 additions & 5 deletions packages/eslint-plugin/lib/rules/no-trailing-spaces.js
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Original file line number Diff line number Diff line change
Expand Up @@ -3,7 +3,7 @@
* @import {CommentContent, Text} from "@html-eslint/types";
*/

const { parse } = require("@html-eslint/template-parser");
const { getCachedParseResult } = require("./utils/template-cache");
const { RULE_CATEGORY } = require("../constants");
const {
getTemplateTokens,
Expand Down Expand Up @@ -107,10 +107,9 @@ module.exports = {
},
TaggedTemplateExpression(node) {
if (shouldCheckTaggedTemplateExpression(node, context)) {
const { html, tokens } = parse(
const { html, tokens } = getCachedParseResult(
node.quasi,
getSourceCode(context),
{}
getSourceCode(context)
);
const lines = codeToLines(html);
check(
Expand All @@ -127,7 +126,10 @@ module.exports = {
},
TemplateLiteral(node) {
if (shouldCheckTemplateLiteral(node, context)) {
const { html, tokens } = parse(node, getSourceCode(context), {});
const { html, tokens } = getCachedParseResult(
node,
getSourceCode(context)
);
const lines = codeToLines(html);
check(
html,
Expand Down
36 changes: 36 additions & 0 deletions packages/eslint-plugin/lib/rules/utils/template-cache.js
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Original file line number Diff line number Diff line change
@@ -0,0 +1,36 @@
/**
* @import {TemplateLiteral} from "@html-eslint/types";
* @import {DocumentNode, AnyToken} from "es-html-parser";
* @import {SourceCode} from "eslint";
*/

const { parse } = require("@html-eslint/template-parser");

/**
* Cache for parsed template literals to avoid re-parsing the same template multiple times.
* Uses WeakMap for automatic garbage collection when nodes are no longer referenced.
* @type {WeakMap<TemplateLiteral, {ast: any, html: string, tokens: any[]}>}
*/
const templateCache = new WeakMap();

/**
* Get or create cached parse result for a template literal.
* @param {TemplateLiteral} node
* @param {SourceCode} sourceCode
* @returns {{ast: DocumentNode, html: string, tokens: AnyToken[]}}
*/
function getCachedParseResult(node, sourceCode) {
// Check if we already have a cached result for this node
const cachedResult = templateCache.get(node);
if (cachedResult) {
return cachedResult;
}

// Parse and cache the result
const result = parse(node, sourceCode, {});
templateCache.set(node, result);

return result;
}

module.exports = { getCachedParseResult };
12 changes: 9 additions & 3 deletions packages/eslint-plugin/lib/rules/utils/visitors.js
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Original file line number Diff line number Diff line change
Expand Up @@ -6,7 +6,8 @@ const {
shouldCheckTaggedTemplateExpression,
shouldCheckTemplateLiteral,
} = require("./settings");
const { parse } = require("@html-eslint/template-parser");
const { getCachedParseResult } = require("./template-cache");
const { traverse } = require("@html-eslint/template-parser/lib/traverser");
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Copilot AI Jul 17, 2025

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[nitpick] The traverse import and usage pattern is duplicated across multiple rule files. Consider centralizing a helper that wraps parse + traverse to reduce boilerplate and ease future updates.

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const { getSourceCode } = require("./source-code");

/**
Expand All @@ -18,12 +19,17 @@ function createTemplateVisitors(context, visitors) {
return {
TaggedTemplateExpression(node) {
if (shouldCheckTaggedTemplateExpression(node, context)) {
parse(node.quasi, getSourceCode(context), visitors);
const { ast } = getCachedParseResult(
node.quasi,
getSourceCode(context)
);
traverse(ast, visitors, null);
}
},
TemplateLiteral(node) {
if (shouldCheckTemplateLiteral(node, context)) {
parse(node, getSourceCode(context), visitors);
const { ast } = getCachedParseResult(node, getSourceCode(context));
traverse(ast, visitors, null);
}
},
};
Expand Down
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