Mongodb Realm every function produces unexpected error, nothing shows in logs

[SirSwagon_N_A]

My functions just end with unexpected error every time and do not show anything in the Realm logs (I turned on logs in each of the function’s settings). I tried user authentication functions, system functions, runAsSystemUser=true, etc.

My setup is Atlas DB, Realm Web App, connect to Realm from Android Java SDK. I have users set up and log in with email and password from Java SDK before running a function. I initialize Realm and the MongodbApp. then call the function with functions.callFunctionAsync(name, parameters, callback). Function codes are very simple and don’t produce errors when I run them directly from Realm UI.

Example functions I tried:

exports = async function(arg){
        let collection = context.services.get("mongodb-atlas").db(<Database>).collection(<Collection>);
        let res = await collection.find({_id:BSON.ObjectId(<ID that exists>}).toArray();
        res = "found: " + res;
        if( context.user ){
          res += "\nUsername is " + context.user.toString();
        }
        res += "\nRunning as system user: " + context.runningAsSystem() + ".";
        return res;
};

and

exports = async function(arg){
  let collection = context.services.get("mongodb-atlas").db(<DB>).collection(<Collection>);
        
        let erg = await collection.updateOne({_id:BSON.ObjectId(<some id that exists>)}, {name:"New Name"});
        res = "Changed #: " + erg.modifiedCount;
        return res;
  
};

[SirSwagon_N_A]

*** FINALLY FIXED ***
It’s about how you call the function. You have to put a List-object in the ‘parameters’ parameter (which is the second in the java sdk) of the callFunction[Async] function. Even if your Realm function is defined without parameters (e.g. just exports = function() {...} or exports = async function() {...}) you can NOT put null as the ‘parameters’. The simplest thing to put is new ArrayList(), like this:

functions.callFunctionAsync('functionName', new ArrayList<String>(), ReturnType.class, new App.Callback<ReturnType>() {...});

No hate but I think it’s so sad that simple stuff like this is not stated in the documentations.