Call logging class

[so195]

I am trying to add a logger to my langium project. I implemented the following class which works when I call it from another file in the console.

import { Logger, createLogger, transports } from "winston";

export default class AppLogger {
        public static Logger: Logger;
      
        public static InitialiseLogger( ) {
          const logger = createLogger({
            transports: [
              new transports.File({ filename: "log.log" }),
            ],
         });
      
          AppLogger.Logger = logger;

          AppLogger.LogInfo("AppLogger", `Info 1`);
         }

       public static LogInfo(label: string, message: string) {
          AppLogger.Logger.info({ label, message });
        }
  }

When I call my logger function from my main.ts file and just start my program, it doesn't work.
This is the code I wrote in my main file:

AppLogger.InitialiseLogger();
AppLogger.LogInfo("main file", `Info 3`);

I also tried logging from other points in my program, but there also nothing happens.
I don't get any error. I am assuming I am not calling my function correctly.

What is the correct way and the correct place to call such a function, so that I can use it throughout my whole application?

[msujew]

Hey @so195,

Can you provide a reproducible example? Note that language servers are not allowed to write to the normal stdio console (they get re-routed instead), as the stdio channel is usually used by the language client to transfer messages.

[so195]

Is there any way to allow writing to the console? But if that isn't possible it would be even more important to be able to write a log file.

To minimize any other influences, I used the hello world project from the langium tutorial.
I only added my file appLogger.ts in the src folder:

import { Logger, createLogger, transports } from "winston";

export default class AppLogger {
  public static Logger: Logger;

  public static InitialiseLogger() {
    const logger = createLogger({
      transports: [new transports.File({ filename: "log.log" })],
    });

    AppLogger.Logger = logger;

    AppLogger.LogInfo("AppLogger", `Info 1`);
  }
  public static LogInfo(label: string, message: string) {
    AppLogger.Logger.info({ label, message });
  }
}

And I added the last two lines to my main.ts file to initialize and test my logger:

import { startLanguageServer } from "langium/lsp";
import { NodeFileSystem } from "langium/node";
import {
  createConnection,
  ProposedFeatures,
} from "vscode-languageserver/node.js";
import { createHelloWorldServices } from "./hello-world-module.js";
import AppLogger from "../appLogger.js";

// Create a connection to the client
const connection = createConnection(ProposedFeatures.all);

// Inject the shared services and language-specific services
const { shared } = createHelloWorldServices({ connection, ...NodeFileSystem });

// Start the language server with the shared services
startLanguageServer(shared);

AppLogger.InitialiseLogger();
AppLogger.LogInfo("main file", `Info 3`);

[msujew]

Thanks for the code! However, I cannot reproduce your issue, as the library correctly logs the data to a file (in the open VS Code workspace, since it's the cwd of the vscode extension).

{"label":"AppLogger","level":"info","message":"Info 1"}
{"label":"main file","level":"info","message":"Info 3"}

You might want to be a bit more specific about the filepath you're using. Maybe something like __dirname + '/log.log' instead to ensure that the log is created in the same directory where the language server is located?

Is there any way to allow writing to the console?

Note that you can still write to console.log, but the log is rerouted to a different channel - when running in vscode, it will instead be printed in the output log of your language server:

[so195]

Thank your very much, that fixed my Problem!