Currently you can add the validateData attribute on a source column. (see Column attributes)
This allows you to choose between rejecting a value or rejecting a row when the constraints on the column are not met (dataType, maxLength, isMandatory, inputFormat).
If the data is not valid and validateData is true, then the entire record will not be synced into the table.
If the data is not valid and validateData is false, then the specific columns will be nulled out but the record will still sync into the table.