Unexpected output with arrays starting with a null/empty element

[cheseaux]

Take this small example :

public class MyPojo {

    public String[] getVal1() {
        return new String[]{"", "foo"};
    }

    public String[] getVal2() {
        return new String[]{null, "bar"};
    }

    public String[] getVal3() {
        return new String[]{"baz",null};
    }

    public static void main(String[] args) throws JsonProcessingException {
        MyPojo jacksonBug = new MyPojo();
        CsvMapper mapper = new CsvMapper();
        String csvContent = mapper.writer(mapper.schemaFor(MyPojo.class).withHeader()).writeValueAsString(jacksonBug);
        System.out.println(csvContent);
    }

}

Output is :

val1,val2,val3
foo,bar,baz;

But should be :

val1,val2,val3
;foo,;bar,baz;

[cowtowncoder]

Which version?

[cheseaux]

Sorry, forgot to mention it : v 2.6.1 but was also present in 2.5

[cheseaux]

Ok, I've found where the bug is.

In CsvGenerator.java, the two methods _addToArray inserts the array separator character if at least one character was already appended to _arrayContents :

protected void _addToArray(String value) {
    if (_arrayContents.length() > 0) {
        _arrayContents.append((char) _arraySeparator);
    }
    _arrayContents.append(value);
}

protected void _addToArray(char[] value) {
    if (_arrayContents.length() > 0) {
        _arrayContents.append((char) _arraySeparator);
    }
    _arrayContents.append(value);
}

But when the first element of the array is empty or null, then this condition will return false and no array separator character will be appended.

This doesn't seem to be easily solvable, but I'll keep you updated if I find something.