Contribute to json language server with a custom language. (#198583)

* Contribute to json language server with a custom language.

* Add `snippets` to `"activationEvents"`

* Remove hardcoded `snippets` from `documentSettings`

* Fix wrong variable in `!isEqualSet()`

* Use `extensions.allAcrossExtensionHosts` instead of `extensions.all`

* enable `"enabledApiProposals"` for `extensions.allAcrossExtensionHosts`

* Fix error: `Property 'allAcrossExtensionHosts' does not exist on type 'typeof extensions'`

* Remove `snippets`

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

@@ -0,0 +1,89 @@
+/*---------------------------------------------------------------------------------------------
+ *  Copyright (c) Microsoft Corporation. All rights reserved.
+ *  Licensed under the MIT License. See License.txt in the project root for license information.
+ *--------------------------------------------------------------------------------------------*/
+
+import { DocumentSelector } from 'vscode-languageclient';
+import { Event, EventEmitter, extensions } from 'vscode';
+
+/**
+ * JSON language participant contribution.
+ */
+interface LanguageParticipantContribution {
+	/**
+	 * The id of the language which participates with the JSON language server.
+	 */
+	languageId: string;
+	/**
+	 * true if the language allows comments and false otherwise.
+	 * TODO: implement server side setting
+	 */
+	comments?: boolean;
+}
+
+export interface LanguageParticipants {
+	readonly onDidChange: Event<void>;
+	readonly documentSelector: DocumentSelector;
+	hasLanguage(languageId: string): boolean;
+	useComments(languageId: string): boolean;
+	dispose(): void;
+}
+
+export function getLanguageParticipants(): LanguageParticipants {
+	const onDidChangeEmmiter = new EventEmitter<void>();
+	let languages = new Set<string>();
+	let comments = new Set<string>();
+
+	function update() {
+		const oldLanguages = languages, oldComments = comments;
+
+		languages = new Set();
+		languages.add('json');
+		languages.add('jsonc');
+		comments = new Set();
+		comments.add('jsonc');
+
+		for (const extension of extensions.allAcrossExtensionHosts) {
+			const jsonLanguageParticipants = extension.packageJSON?.contributes?.jsonLanguageParticipants as LanguageParticipantContribution[];
+			if (Array.isArray(jsonLanguageParticipants)) {
+				for (const jsonLanguageParticipant of jsonLanguageParticipants) {
+					const languageId = jsonLanguageParticipant.languageId;
+					if (typeof languageId === 'string') {
+						languages.add(languageId);
+						if (jsonLanguageParticipant.comments === true) {
+							comments.add(languageId);
+						}
+					}
+				}
+			}
+		}
+		return !isEqualSet(languages, oldLanguages) || !isEqualSet(comments, oldComments);
+	}
+	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); },
+		useComments(languageId: string) { return comments.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;
+}