[GitHub] [commons-csv] davidmoten opened a new pull request #41: [CSV-239] Add CSVRecord.getHeaderNames and allow duplicate headers

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davidmoten opened a new pull request #41: [CSV-239] Add CSVRecord.getHeaderNames and allow duplicate headers
URL: https://github.com/apache/commons-csv/pull/41
 
 
   These are the changes:
   
   * add `getHeaderNames` returns all headers in column order including repeats which are allowed in general as per RFC 4180
   * add `CSVFormat.withAllowDuplicateHeaderNames()`. `CSVFormat.DEFAULT` now allows duplicate header names because RFC 4190 allows non-unique header names. This is a behavioural change but not a breaking API change anywhere because there is no API contract for it (e.g. javadoc). Because `CSVFormat.DEFAULT` should reflect RFC 4190 I'd classify this as a bug fix.
   * `CSVFormat` is `Serializable` which means adding new fields to it (`allowDuplicateHeaderNames`) is theoretically a breaking change. I propose we allow this minor breaking change and also propose that `CSVFormat` does not implement `Serializable` in 2.x
   * fix `CSVRecord.toMap` javadoc
   * fix bug in `CSVParser` where an IAE is thrown with a message about duplicate headers when the problem was actually a missing header name
   * add test coverage 
   
   Question:
   * do we need to talk about HeaderNames when we could just say Header?
   
   Not addressed:
   * would be nice if `CSVRecord.toMap` returned a Map whose entries are iterable in column order but this involves quite a bit of rework so will leave for another PR (probably for 2.x).
   * `CSVRecord.get(String)` should ideally throw when two columns with that header name exist
   
   Notes for 2.x: 
   * for consistency `CSVFormat.withAllowMissingColumnNames` should be `CSVFormat.withAllowMissingHeaderNames`
   * remove `Serializable` from `CSVFormat`
   * `CSVFormat.withIgnoreHeaderCase` creates problems and lacks flexibility. I'd suggest `CSVRecord.getIgnoreCase(int)` instead
   
   

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