How to get the root cause of an unhandled trigger error?

Question

If I have some code doing DML which runs a trigger, and then that trigger throws an unhandled exception, how can I get the real cause of the problem?

For example, suppose I have a really dumb trigger:

trigger AccountTrigger on Account (after insert) {
    insert new Lead();
}

This will always fail because it's not specifying the required fields for Lead.

Then, I write a test to see whether or not I can catch the cause of the exception to be REQUIRED_FIELD_MISSING:

@IsTest
private class ChainedTriggerErrorTest {

    static Account toInsert = new Account(Name = 'ACME');

    @IsTest
    static void allOrNothingFalse() {

        Database.SaveResult result = Database.insert(toInsert, false);

        System.assertEquals(1, result.getErrors().size());
        Database.Error theError = result.getErrors()[0];
        System.assertEquals(StatusCode.CANNOT_INSERT_UPDATE_ACTIVATE_ENTITY, theError.getStatusCode());
        System.assert(theError.getMessage().contains(StatusCode.REQUIRED_FIELD_MISSING.name()));

        System.debug(theError.getMessage());
    }

    @IsTest
    static void tryCatch() {
        try {
            insert toInsert;
        } catch (DmlException e) {
            System.assertEquals(StatusCode.CANNOT_INSERT_UPDATE_ACTIVATE_ENTITY, e.getDmlType(0));
            System.assertEquals(null, e.getCause());
            System.assert(e.getMessage().contains(StatusCode.REQUIRED_FIELD_MISSING.name()));

            System.debug(e.getMessage());
        }
    }
}

All of those assertions pass i.e. both methods of trapping the errors only reveal on cause, and that cause is CANNOT_INSERT_UPDATE_ACTIVATE_ENTITY. So, you're stuck with searching the text body of the message to see what the real cause is. 

It seems insane that e.getCause() returns null when the debug of e.getMessage() is:

Insert failed. First exception on row 0; first error: CANNOT_INSERT_UPDATE_ACTIVATE_ENTITY, AccountTrigger: execution of AfterInsert

caused by: System.DmlException: Insert failed. First exception on row 0; first error: REQUIRED_FIELD_MISSING, Required fields are missing: [LastName, Company]: [LastName, Company]

Trigger.AccountTrigger: line 7, column 1: []

(Emphasis mine)

Obviously, this is a bit of a fake scenario, but the real-world problem could be something like catching a row lock error. I want to catch it at the top-level and just try again later. And I'd rather do that in a better way than scraping the error message. Is there any better way?

Answer 1

That's because you have nested exceptions, so the code is only seeing the higher level one, to be able to see both, both of them need to be explictly thrown/catch, for example

On account trigger

 public static void beforeInsert(List<Account> newRecords) {


    try{
        insert new lead();
    }catch(Exception e){
        System.debug('low level exception: '+e.getDmlType(0));
        throw e;
    }

Then on the developer console (or your calling class)

Account a = new Account();
a.Name = 'Hello';

try{
    insert a;
}catch(Exception e){
    System.debug('high level exception: '+e.getDmlType(0));

}

Then in the debug log I can see both exception types