Merge from vscode merge-base (#22780)

* Revert "Revert "Merge from vscode merge-base (#22769)" (#22779)"

This reverts commit 47a1745180.

* Fix notebook download task

* Remove done call from extensions-ci

extensions/html-language-features/client/src/languageParticipants.ts

@@ -0,0 +1,87 @@
+/*---------------------------------------------------------------------------------------------
+ *  Copyright (c) Microsoft Corporation. All rights reserved.
+ *  Licensed under the Source EULA. See License.txt in the project root for license information.
+ *--------------------------------------------------------------------------------------------*/
+
+import { DocumentSelector } from 'vscode-languageclient';
+import { Event, EventEmitter, extensions } from 'vscode';
+
+/**
+ * HTML language participant contribution.
+ */
+interface LanguageParticipantContribution {
+	/**
+	 * The id of the language which participates with the HTML language server.
+	 */
+	languageId: string;
+	/**
+	 * true if the language activates the auto insertion and false otherwise.
+	 */
+	autoInsert?: boolean;
+}
+
+export interface LanguageParticipants {
+	readonly onDidChange: Event<void>;
+	readonly documentSelector: DocumentSelector;
+	hasLanguage(languageId: string): boolean;
+	useAutoInsert(languageId: string): boolean;
+	dispose(): void;
+}
+
+export function getLanguageParticipants(): LanguageParticipants {
+	const onDidChangeEmmiter = new EventEmitter<void>();
+	let languages = new Set<string>();
+	let autoInsert = new Set<string>();
+
+	function update() {
+		const oldLanguages = languages, oldAutoInsert = autoInsert;
+
+		languages = new Set();
+		languages.add('html');
+		autoInsert = new Set();
+		autoInsert.add('html');
+
+		for (const extension of extensions.allAcrossExtensionHosts) {
+			const htmlLanguageParticipants = extension.packageJSON?.contributes?.htmlLanguageParticipants as LanguageParticipantContribution[];
+			if (Array.isArray(htmlLanguageParticipants)) {
+				for (const htmlLanguageParticipant of htmlLanguageParticipants) {
+					const languageId = htmlLanguageParticipant.languageId;
+					if (typeof languageId === 'string') {
+						languages.add(languageId);
+						if (htmlLanguageParticipant.autoInsert !== false) {
+							autoInsert.add(languageId);
+						}
+					}
+				}
+			}
+		}
+		return !isEqualSet(languages, oldLanguages) || !isEqualSet(oldLanguages, oldAutoInsert);
+	}
+	update();
+
+	const changeListener = extensions.onDidChange(_ => {
+		if (update()) {
+			onDidChangeEmmiter.fire();
+		}
+	});
+
+	return {
+		onDidChange: onDidChangeEmmiter.event,
+		get documentSelector() { return Array.from(languages); },
+		hasLanguage(languageId: string) { return languages.has(languageId); },
+		useAutoInsert(languageId: string) { return autoInsert.has(languageId); },
+		dispose: () => changeListener.dispose()
+	};
+}
+
+function isEqualSet<T>(s1: Set<T>, s2: Set<T>) {
+	if (s1.size !== s2.size) {
+		return false;
+	}
+	for (const e of s1) {
+		if (!s2.has(e)) {
+			return false;
+		}
+	}
+	return true;
+}