Dynamodb missing error with ADD empty set

[jasonrdunne]

This error is caught by aws, but not with moto:

ExpressionAttributeValues contains invalid value: One or more parameter values were invalid: An number set may not be empty for key :deletedConversationIds

It's caused by an update like this:

        user_table.update_item(
            TableName="Users",
            Key={"userId": user_id},
            UpdateExpression="ADD stringSet :emptySet",
            ExpressionAttributeValues={
                ":emptySet": empty_set,
            },
        )

[jasonrdunne]

I found another similar issue:

if an ExpressionAttributeValue is defined and not used, it errors in real aws, but not moto:

Value provided in ExpressionAttributeValues unused in expressions: keys: {:variable}

[bblommers]

Hi @jasonrdunne, thanks for raising these! I'll open a PR to add validation for the first issue in a second.

Do you have an example for the second issue? The following code does throw an error in Moto:

dynamodb.update_item(
            TableName=table_name,
            Key={"pk": {"S": "foo"}},
            UpdateExpression="ADD stringset :emptySet",
            ExpressionAttributeValues={":emptySet": {"SS": ()}, "other": {"S": "data"}},
        )