How can I read tags of an app?

So I was trying to sort apps into groups based on their tag, but when I try to get the tag by writing it to the launchCache it returns undefined when I try and use it. The other properties seem to work, so I'm not sure why the tags don't. I checked the .info files on my Bangle and they all have the tags property.

  let s = require("Storage");
  
  let launchCache = s.readJSON("launch.cache.json", true) || {};
  let launchHash = require("Storage").hash(/\.info/);
  if (launchCache.hash != launchHash) {
    launchCache = {
      hash: launchHash,
      apps: s.list(/\.info$/)
        .map(app => { var a = s.readJSON(app, 1); return a && { name: a.name, type: a.type, icon: a.icon, sortorder: a.sortorder, src: a.src, tags: a.tags}; }) // added tags: a.tags
        .filter(app => app && (app.type == "app" || (app.type == "clock" && settings.showClocks) || !app.type))
        .sort((a, b) => {
          var n = (0 | a.sortorder) - (0 | b.sortorder);
          if (n) return n; 
          if (a.name < b.name) return -1;
          if (a.name > b.name) return 1;
          return 0;
        })
    };
    s.writeJSON("launch.cache.json", launchCache);
  }
  let apps = launchCache.apps;
  apps.forEach(app => {
    if (app.icon)
      {app.icon = s.read(app.icon);}
      console.log(app.tags)//returns undefined

  });