app script web app can't access google docs if anonymous

Question

Goal: create an apps script web app that opens a google doc and returns it's name

This functionality stopped working sometime in the last month or so.

• create apps script project
• add a doGet

function doGet(e) {
    var msg = "none;";
    try{
      var doc = DocumentApp.openById("1WYNw9IPcsYZXrvK7gOaoOLt7GPiaUhCJ5OEf79h~~~~"); 
      msg = doc.getName();
    }catch(e){
      msg = e;
    }  
    return HtmlService.createHtmlOutput(msg);  
}

Save and follow path for authentication

Publish / Deploy as web app with settings

• new version because anon unable to use dev version of url
• execute as me
• Anyone, even anonymous

Now try it out

• open the url in authenticated browser
  • not the test url
  • success

Found and opened Intro

open the url in incognito and do not login to any account

Error message

Exception: We're sorry, a server error occurred. Please wait a bit and try again.

Edit : added the line msg = doc.getName();

Answer 1

This works for me even including a new incognito window and another account.

function doGet(e) {
    var msg = "none;";
    try{
      var doc = DocumentApp.openById("docid"); 
      msg = doc.getName();
    }catch(e){
      msg = e;
    }  
    return ContentService.createTextOutput(msg);
}