null in reader

[petrvosahlo-cnrd]

Hello @osiegmar,
what would propose as solution for handling nulls instead of empty strings?

I created field modifier to handle empty string to null.
IE: "public enum CustomFieldModifier implements FieldModifier {

NULL {

@Override
public String modify(final long startingLineNumber, final int fieldIdx, final boolean quoted, final String field) {
        if (!StringUtils.hasText(field))
            return null;

        return field;
}

}"

later commonly used as
"try (var reader = CsvReader.builder().skipEmptyLines(true).build(NamedCsvRecordHandler.of(c -> c.fieldModifier(CustomFieldModifier.NULL)), csvAsString)) {
return reader.stream().map(this::convertToEntity).toList();
}"

but later in de.siegmar.fastcsv.reader.AbstractInternalCsvCallbackHandler.addField(char[], int, int, boolean) we are doing null.lenght()

So whats the prefered way to handle "" -> null? How to keep NamedCsvRecordHandler functionality without overiding quite a lot from fastcsv package?

[osiegmar]

FastCSV provides a null-free API, ensuring that no public function ever returns null.

If a field modifier were allowed to return null, the documented behavior of methods like CsvRecord.getField() would no longer hold true and would break the API contract. Therefore, all field modifiers must return a non-null value, as documented in the FieldModifier documentation:

the value passed to the function is never null and the return value must not be null.

I have created an example that shows how to handle null values in FastCSV by using a custom FieldModifier. I hope this helps!