Emmet create new html-matcher override instead of using LS (#113508)

extensions/emmet/src/parseDocument.ts

@@ -0,0 +1,46 @@
+/*---------------------------------------------------------------------------------------------
+ *  Copyright (c) Microsoft Corporation. All rights reserved.
+ *  Licensed under the MIT License. See License.txt in the project root for license information.
+ *--------------------------------------------------------------------------------------------*/
+
+import { TextDocument } from 'vscode';
+import { Node as FlatNode } from 'EmmetFlatNode';
+import parse from '@emmetio/html-matcher';
+import parseStylesheet from '@emmetio/css-parser';
+import { isStyleSheet } from './util';
+
+type Pair<K, V> = {
+	key: K;
+	value: V;
+};
+
+// Map(filename, Pair(fileVersion, rootNodeOfParsedContent))
+const _parseCache = new Map<string, Pair<number, FlatNode> | undefined>();
+
+export function getRootNode(document: TextDocument, useCache: boolean): FlatNode {
+	const key = document.uri.toString();
+	const result = _parseCache.get(key);
+	const documentVersion = document.version;
+	if (useCache && result) {
+		if (documentVersion === result.key) {
+			return result.value;
+		}
+	}
+
+	const parseContent = isStyleSheet(document.languageId) ? parseStylesheet : parse;
+	const rootNode = parseContent(document.getText());
+	if (useCache) {
+		_parseCache.set(key, { key: documentVersion, value: rootNode });
+	}
+	return rootNode;
+}
+
+export function addFileToParseCache(document: TextDocument) {
+	const filename = document.uri.toString();
+	_parseCache.set(filename, undefined);
+}
+
+export function removeFileFromParseCache(document: TextDocument) {
+	const filename = document.uri.toString();
+	_parseCache.delete(filename);
+}