The idea is to Automatically follow all other chatter users when a new user is added.

The problem I am having is the trigger works when adding a new user as long as a Role is not specified upon creation.

When a Role is selected during creation the following error occurs.

caused by: System.DmlException: Insert failed. First exception on row 0; first error: MIXED_DML_OPERATION, DML operation on setup object is not permitted after you have updated a non-setup object (or vice versa): EntitySubscription, original object: User: []

Below is the trigger I have written:

trigger FollowAllChatterUsers on User (after insert) {
    //Create List to hold all chatterIds. they will need to be added.
    List<User> chatterIdsToAdd = new List<User>([SELECT Id from User WHERE IsActive = true]);
    Id currentUserId;
    
    //Take a count of how many users were added to fire this trigger.
    //If more than 10 then do not automatically follow.
    //The assumption is that if we batch-add more than 10 records we are probably
    //  loading saved data or backup data in which case the entitysubscriptions table
    //  will need to be loaded as well.
    Integer triggerLength = 0;
    for( User usr: Trigger.new ) {
        triggerLength++;
    }
    
    if (triggerLength <= 10) {
        // for each inserted user add all chatter ids except their own.
        for( User usr: Trigger.new ) {
            //Array of subscription records to create
            EntitySubscription[] subsToCreate = new EntitySubscription[]{};
            //Get the id of the current user.
            currentUserId = usr.Id;
            //Loop through list of users to add.
            for( User toAdd: chatterIdsToAdd ) {
                //If the id to add is our own then skip. otherwise cont..
                if ( toAdd.Id != currentUserId ) {
                    //Create the EntitySubscription record.
                    EntitySubscription follow = new EntitySubscription(
                        parentId = toAdd.Id,
                        subscriberId = currentUserId);
                    //Add new EntitySubscription to Array for insertion. 
                    subsToCreate.add(follow);
                }
            }
            //Insert the array.
            insert subsToCreate;
        }
    }
}

I read somewhere that within the same transaction a User record and a Role record cannot be update using DML.

I'm not sure if that the same issue I'm running into or not.

If anyone has any insight I would welcome your suggestions.

Thank You,

    Ramon