[jira] [Work logged] (CSV-253) Handle absent values in input (null)

["ASF GitHub Bot (Jira)" <ji...@apache.org>]

     [ https://issues.apache.org/jira/browse/CSV-253?focusedWorklogId=335197&page=com.atlassian.jira.plugin.system.issuetabpanels:worklog-tabpanel#worklog-335197 ]

ASF GitHub Bot logged work on CSV-253:
--------------------------------------

                Author: ASF GitHub Bot
            Created on: 28/Oct/19 21:13
            Start Date: 28/Oct/19 21:13
    Worklog Time Spent: 10m 
      Work Description: lbruun commented on pull request #51: [CSV-253] Handle absent values in input
URL: https://github.com/apache/commons-csv/pull/51
 
 
   Being able to appropriately translate an absent value in CSV input with a Java `null` value. Previously, there was no way to do this, such a value would at best become a zero-length string when parsing. This made it impossible to correctly parse CSV output from say databases.
   
   In reference to [CSV-253](https://issues.apache.org/jira/browse/CSV-253).
   
   The PR addresses the issue by adding a flag on `Token` so that it becomes possible to distinguish between a token which is the result of an absent value in input or an actual zero-length string. A new modifier, `absentIsNull` is introduced on `CSVFormat`.   All existing formats and functionality is kept as-is, meaning the new feature is fully based on opt-in.
   
   As a possible next step the pre-defined CSV formats for databases (i.e. `INFORMIX_UNLOAD_CSV`, `MYSQL`, `ORACLE` and `POSTGRESQL_CSV`) should be reviewed. I suspect that at least `POSTGRESQL_CSV` has always been incorrect in this matter. With this PR is can be corrected.
   
   
 
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Issue Time Tracking
-------------------

            Worklog Id:     (was: 335197)
    Remaining Estimate: 0h
            Time Spent: 10m

> Handle absent values in input (null)
> ------------------------------------
>
>                 Key: CSV-253
>                 URL: https://issues.apache.org/jira/browse/CSV-253
>             Project: Commons CSV
>          Issue Type: Improvement
>          Components: Parser
>            Reporter: Lars Bruun-Hansen
>            Priority: Major
>          Time Spent: 10m
>  Remaining Estimate: 0h
>
> The parser must be able to handle absent values in input and translate that into {{null}} as required. I see several tickets on this matter in the history, but none seem to have addressed the issue, at least not for parsing. 
> For this problem, I see a need to introduce a new term:
> Definition: _Absent value_ is when there are zero characters between field delimiters.
> Specifically the aim is to be able to parse the following:
> {noformat}
>     "John",,"Doe"    // 2nd element is absent
>     ,"AA",123        // 1st element is absent
>     "John",90,       // 3rd element is absent
>     "",,90           // 2nd element is absent (1st element isn't)
> {noformat}
>  
> See also CSV-93 which I think never addressed the issue, probably because the reporter was happy with having the issue fixed for CSV output, not for parsing.
> A PR is coming...



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