DMLException.getDmlFields Fails When Inserting List of SObjects?

Question

When a DML operation on a list of records of a concrete object type, e.g. Account fails, calling getDmlFields on the thrown DMLException returns the fields that caused the failure, as described in the docs.

But when a DML operation on a List<SObject> fails, getDmlFields returns null.

Here's an example:

force apex <<EOF
try {
   insert new List<Account>{new Account()};
} catch (DMLException e) {
   for (Integer i = 0; i < e.getNumDml(); i++) {
      System.debug('FAILED INSERTING ACCOUNT');
      System.debug('ERROR FIELD NAMES');
      System.debug(e.getDmlFieldNames(i));
      System.debug('ERROR FIELDS');
      System.debug(e.getDmlFields(i));
   }
}
try {
   insert new List<SObject>{new Account()};
} catch (DMLException e) {
   for (Integer i = 0; i < e.getNumDml(); i++) {
      System.debug('FAILED INSERTING SOBJECT');
      System.debug('ERROR FIELD NAMES');
      System.debug(e.getDmlFieldNames(i));
      System.debug('ERROR FIELDS');
      System.debug(e.getDmlFields(i));
   }
}
EOF

In both cases, a validation rule on the Type field causes the insert to fail. The call to getDmlFieldNames returns Type in both cases, but in the second case, the call to getDmlFields returns null.

15:41:36.15 (39209292)|CODE_UNIT_STARTED|[EXTERNAL]|Validation:Account:new
15:41:36.15 (39398837)|CODE_UNIT_FINISHED|Validation:Account:new
15:41:36.15 (40276287)|EXCEPTION_THROWN|[2]|System.DmlException: Insert failed. First exception on row 0; first error: FIELD_CUSTOM_VALIDATION_EXCEPTION, Type is required for Referral Accounts: [Type]
15:41:36.15 (40838118)|USER_DEBUG|[5]|DEBUG|FAILED INSERTING ACCOUNT
15:41:36.15 (40861711)|USER_DEBUG|[6]|DEBUG|ERROR FIELD NAMES
15:41:36.15 (40965320)|USER_DEBUG|[7]|DEBUG|(Type)
15:41:36.15 (40987483)|USER_DEBUG|[8]|DEBUG|ERROR FIELDS
15:41:36.15 (41104191)|USER_DEBUG|[9]|DEBUG|(Type)
15:41:36.15 (43357699)|CODE_UNIT_STARTED|[EXTERNAL]|Validation:Account:new
15:41:36.15 (43515984)|CODE_UNIT_FINISHED|Validation:Account:new
15:41:36.15 (44175767)|EXCEPTION_THROWN|[13]|System.DmlException: Insert failed. First exception on row 0; first error: FIELD_CUSTOM_VALIDATION_EXCEPTION, Type is required for Referral Accounts: [Type]
15:41:36.15 (44572412)|USER_DEBUG|[16]|DEBUG|FAILED INSERTING SOBJECT
15:41:36.15 (44591105)|USER_DEBUG|[17]|DEBUG|ERROR FIELD NAMES
15:41:36.15 (44656270)|USER_DEBUG|[18]|DEBUG|(Type)
15:41:36.15 (44676099)|USER_DEBUG|[19]|DEBUG|ERROR FIELDS
15:41:36.15 (44719764)|USER_DEBUG|[20]|DEBUG|null

Is this expected behavior or a Salesforce bug?

Answer 1

According to support, this is as designed, although it seems more like an oversight than a design decision to me. In any case, it should be documented.

From support:

The behavior that we see when we are using List is working as designed. Please find the detailed summary for the same below

-- The getDMLFieldName's return type is String[] whereas getDMLFields return type is Schema.sObjectField[]

which means the getDMLFields has to make a describe call to get the fields. The describe call looks something like follows

Account.sObjectType.getDescribe();

We need concrete SObject Types like Account or Opportunity to get this Describe call working. As Heterogeneous list List cannot be used to get the instance and map it to the describe call.

Hence kindly use Homogeneous List types like List or List to get the getDMLFields() working.

As a work-around, you can get the SObjectField if you keep a reference to the list of SObjects on which the failed DML operation was performed.

List<SObject> sobjects = new List<SObject>{new Account()};
try {
   insert sobjects;
} catch (DMLException e) {
  for (Integer i = 0; i < e.getNumDml(); i++) {
    // Get the list of field names, which may not be globally unique,
    // but will be unique for a single SObject
    List<String> fieldNames = e.getDmlFieldNames(i);
    // Get the SObjectType for the record that failed
    Integer insertIndex = e.getDmlIndex(i);
    Schema.SObjectType failedType =   sobjects[insertIndex].getSObjectType();
    for (String fieldName : fieldNames) {
      // Use the field name to get the SObjectField
      Schema.SObjectField fieldFromName = failedType.getDescribe().fields.getMap().get(fieldName);
      System.debug('SOBJECT FIELD FROM NAME');
      System.debug(fieldFromName);
    }
  }
}