PnP.Core hides SPDuplicateValuesFoundException

[nuverlon]

Hi everyone,

I'm running into a situation where PnP.Core hides the actual SharePoint error when inserting an item into a list that has a unique-value constraint on a column.

PnP.Core

In PnP.Core using list.Items.AddAsync(fields), a duplicate violation throws:
SharePointRestServiceException: There was an exception while writing field [FieldName]. Verify you're using the correct InternalName value for the field you want to write to.

Error-Property of Exception is null. Message is too generic, there is no way to distinguish a duplicate value error from a wrong field name.

CSOM

In CSOM using Microsoft.SharePoint.Client.ClientContext with ExecuteQueryAsync, a duplicate violation throws a ServerException with full details directly on the exception:
ServerErrorCode = -2130575169 HResult = -2146233088 ServerErrorTypeName = "Microsoft.SharePoint.SPDuplicateValuesFoundException" Message = "The list item could not be added or updated because duplicate values were found in the following field(s) in the list: [FieldName]"

Is there a supported way with PnP.Core to get the ErrorCode / ErrorMessage out of SharePointRestServiceException without falling back to CSOM?

[Adam-it]

That is some good question and feedback.
I think the problem is that here

pnpcore/src/sdk/PnP.Core/Model/SharePoint/Core/Internal/ListItem.cs

Lines 190 to 217 in 07bd476

	private void HandleValidateAddAndUpdateResponse(JsonElement field, JsonElement value, string fieldName, Guid batchRequestId)
	{
	// In some cases SharePoint will return HTTP 200 indicating the list item was added ok, but one or more fields could
	// not be added which is indicated via the HasException property on the field. If so then throw an error.
	if (field.TryGetProperty("HasException", out JsonElement hasExceptionProperty) && hasExceptionProperty.GetBoolean() == true)
	{
	bool handled = false;
	if (batchRequestId != Guid.Empty)
	{
	var actualBatch = PnPContext.BatchClient.GetBatchByBatchRequestId(batchRequestId);
	if (!actualBatch.ThrowOnError)
	{
	// Add error to used batch
	actualBatch.AddBatchResult(actualBatch.GetRequest(batchRequestId),
	System.Net.HttpStatusCode.OK,
	value.ToString(),
	new SharePointRestError(ErrorType.SharePointRestServiceError, (int)System.Net.HttpStatusCode.OK, string.Format(PnPCoreResources.Exception_ListItemAdd_WrongInternalFieldName, fieldName)));
	handled = true;
	}
	}
	if (!handled)
	{
	throw new SharePointRestServiceException(string.Format(PnPCoreResources.Exception_ListItemAdd_WrongInternalFieldName, fieldName));
	}
	}
	}

We just read the HasException and handle the error but we do not parse and pass one the error code and error message.
What we could do is:

• Read ErrorCode (int) and ErrorMessage (string) from the field JsonElement
• Construct a SharePointRestError with those details (or pass them into the message)

[Adam-it]

Added an issue for that #1764