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https://issues.apache.org/jira/browse/CSV-302?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=17625644#comment-17625644
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Seth Falco edited comment on CSV-302 at 10/28/22 11:56 AM:
-----------------------------------------------------------
Based on my findings in this PR:
https://github.com/apache/commons-csv/pull/114
While by the names, it sounds like the default should be `DISALLOW`. If we look
at the old code, the default value should actually be `ALLOW_EMPTY`.
When `allowDuplicateHeaderNames` was set to `false`, it still allowed duplicate
empty headers.
> // Note: This will always allow a duplicate header if the header is empty
>
> —
> https://github.com/apache/commons-csv/pull/114/files#diff-4274bff7e18158d8230b2c46e6ab7ae5af153bcd9aa69961d1fbf1faa87fbbfbL500
Edit: Sorry for introducing not considering that meanwhile! It seems I only
tested cases where it was explicitly set, and not the default behavior.
was (Author: sethi):
Based on my findings in this PR:
https://github.com/apache/commons-csv/pull/114
While by the names, it sounds like the default should be `DISALLOW`. If we look
at the old code, the default value should actually be `ALLOW_EMPTY`.
When `allowDuplicateHeaderNames` was set to `false`, it still allowed duplicate
empty headers.
> // Note: This will always allow a duplicate header if the header is empty
>
> —
> https://github.com/apache/commons-csv/pull/114/files#diff-4274bff7e18158d8230b2c46e6ab7ae5af153bcd9aa69961d1fbf1faa87fbbfbL500
> CSVFormat.duplicateHeaderMode requires default for backward compatibility
> -------------------------------------------------------------------------
>
> Key: CSV-302
> URL: https://issues.apache.org/jira/browse/CSV-302
> Project: Commons CSV
> Issue Type: Bug
> Components: Parser
> Affects Versions: 1.x
> Reporter: Markus Spann
> Priority: Minor
> Time Spent: 2.5h
> Remaining Estimate: 0h
>
> The member in class {{CSVFormat}}
> {code:java}
> boolean allowDuplicateHeaderNames{code}
> was recently replaced by
> {code:java}
> DuplicateHeaderMode duplicateHeaderMode{code}
> The boolean defaults to {{{}false{}}}, while the member of type
> {{DuplicateHeaderMode}} defaults to {{{}null{}}}.
> {{duplicateHeaderMode}} must be initialized with {{DISALLOW}} for backward
> compatibility.
> The change is also problematic with regards to serialization. The class is
> serializable and {{serialVersionUID}} is unchanged between versions. The
> boolean setting {{allowDuplicateHeaderNames}} in an object serialized in
> version 1.9.0 or earlier would always be de-serialized to
> {{duplicateHeaderMode = null}} in the current head.
> To handle the code changes correctly, customized de-serialization would need
> to be implemented.
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