Execution of BeforeUpdate caused by: System.FinalException: SObject row does not allow errors ()

Question

I have created a trigger on the Opportunity object for before insert and before update, through which I am sending the Trigger.newMap variable as an argument to my apex class where I am checking the existence of a particular combination against the records in another Object called record combinations and trying to add an error, if a particular pattern of record doesn't exist. But when I try to create an Opportunity or update it I am getting the below exception.

OppRecordCombo: execution of BeforeUpdate caused by: System.FinalException: SObject row does not allow errors () 

My trigger is below

trigger OppRecordCombo on Opportunity (before insert, before update) {
    if((Trigger.isBefore && Trigger.isInsert) || (Trigger.isBefore && Trigger.isUpdate)) {
        OppRecordComboClass opp = new OppRecordComboClass();
        opp.checkComboValidate(Trigger.newMap);
    }
}

And my apex class is as below

public without sharing class OppRecordComboClass {
    //private List<Opportunity> opportunities;
    String recordComboString;
    String oppComboString;
    List<String> recordComboStringList = new List<String>();

    public OppRecordComboClass() {
    }

    public void checkComboValidate(Map<Id, Opportunity> opportunities) {
        try {
            List<Record_Combination__c> recordcombo = [SELECT Client__r.Name,
                                                            Client_SFDC_ID__c,
                                                            Agency__r.Name,
                                                            Agency_SFDC_ID__c
                                                            FROM Record_Combination__c];

            for(Record_Combination__c recComb : recordcombo) {
                recordComboString = recComb.Client__r.Name + recComb.Client_SFDC_ID__c + recComb.Agency__r.Name + recComb.Agency_SFDC_ID__c;
                recordComboStringList.add(recordComboString);
            }

            List<Opportunity> oppCheckList = [SELECT Id,
                                                    Account.Name,
                                                    AccountId,
                                                    Agency_Name__r.Name,
                                                    Agency_Name__c,
                                                    Allow_New_Account_Combination__c
                                                    FROM Opportunity
                                                    WHERE Id in :opportunities.keySet()];

            for(Opportunity opp : oppCheckList) {
                if(opp.Allow_New_Account_Combination__c == false) {
                    oppComboString = opp.Account.Name + opp.AccountId + opp.Agency_Name__r.Name + opp.Agency_Name__c;
                    System.debug('This is the opp combo string akki ' + oppComboString);
                    if(!recordComboStringList.contains(oppComboString)) {
                        //Opportunity triggerOpp = opportunities.get(opp.Id);
                        opportunities.get(opp.Id).addError('This Customer and Agency combination doesn\'t exist in OB. Do you still want to create this Opportunity');
                    }
                }
            }
        } catch(Exception e) {
            System.debug('An exception occured at the line ' + e.getLineNumber() + ' exception is ' + e.getMessage());
        }
    }
}

Can anyone please let me know why is this happening and how can this be corrected?

Answer 1

Trigger is on the before insert and before update. And in your method you're using opportunities map with ID as a key. However in before insert, ID you will not get(its generated after before trigger execution).

Also as per the exception message - You're trying to add an error to record which is not part of trigger context.