VS Code language client with stdio + socket

extension.ts

import * as net from 'net';
import * as vscode from 'vscode';
import { LanguageClient, LanguageClientOptions, ServerOptions, StreamInfo } from 'vscode-languageclient';

const DEBUG = false;
const SERVER_PORT = 5008;

export function activate(context: vscode.ExtensionContext) {
    const languageClient = DEBUG
        ? getSocketLanguageClient({ serverPort: SERVER_PORT })
        : getStdioLanguageClient();

    const disposable = languageClient.start();
    context.subscriptions.push(disposable);
}

export function deactivate() {
}

export function getStdioLanguageClient(): LanguageClient {
    const commandPath: string = '...'; // Obtain or hard-code path to Java language server executable
    const serverOptions: ServerOptions = {
        run: {
            command: commandPath
        },
        debug: {
            command: commandPath,
            args: ['-Xdebug', '-Xrunjdwp:server=y,transport=dt_socket,address=8000,suspend=n,quiet=y', '-Xmx256m']
        }
    };

    const clientOptions: LanguageClientOptions = {
        documentSelector: ['foo'],
    };

    return new LanguageClient('foo', 'Foo Language', serverOptions, clientOptions);
}

interface DebugOptions {
    serverPort: number;
}

export function getSocketLanguageClient({ serverPort }: DebugOptions): LanguageClient {
    const serverOptions: ServerOptions = () => {
        const socket = net.connect({ port: serverPort });
        const result: StreamInfo = {
            writer: socket,
            reader: socket
        };
        return Promise.resolve(result);
    };

    const clientOptions: LanguageClientOptions = {
        documentSelector: ['foo'],
    };

    return new LanguageClient('foo', 'Foo Language', serverOptions, clientOptions);
}