Feature request: Differentiate between empty string and null value #81
Description
readAllWithHeader yields a List<Map<String,String>> and hence empty columns are being read as empty strings, so that we get "" for both col1 and col2 in the following example:
"col1","col2"
"",
I'd really like to get null for col2 here (this of course only makes sense if all strings are quoted, otherwise it wouldn't be clear how to interpret empty columns). I understand that you can't change the result to List<Map<String,String?>> now, but maybe you could add a nullCode option for reading as it already exists for writing. The default value is an empty string "" (=current behavior). I could then simply do
val nullCode = "NULL"
val rows = csvReader(nullCode=nullCode).readAllWithHeader(inputStream)
.map { row -> row.mapValues { col -> if (col.value == nullCode) null else col.value } }
At first glance it seems that it only requires to change
https://github.com/doyaaaaaken/kotlin-csv/blob/c23a51b98fbbcb1348b3928d561f1f5e11fba965/src/commonMain/kotlin/com/github/doyaaaaaken/kotlincsv/parser/ParseStateMachine.kt#L36-L48
to
delimiter -> {
field.append(nullCode)
flushField()
state = ParseState.DELIMITER
}
'\n', '\u2028', '\u2029', '\u0085' -> {
field.append(nullCode)
flushField()
state = ParseState.END
}
'\r' -> {
if (nextCh == '\n') pos += 1
field.append(nullCode)
flushField()
state = ParseState.END
}
but I didn't check it thoroughly.