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From "Doug Cutting (JIRA)" <j...@apache.org>
Subject [jira] [Commented] (AVRO-530) allow for mutual recursion in type definitions
Date Mon, 01 Oct 2012 17:31:08 GMT

    [ https://issues.apache.org/jira/browse/AVRO-530?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=13466984#comment-13466984
] 

Doug Cutting commented on AVRO-530:
-----------------------------------

Yes, that's meant to work today.  Perhaps there's a bug when a record has no other fields
besides a self-reference.  Please file a separate issue for this bug.  Thanks!
                
> allow for mutual recursion in type definitions
> ----------------------------------------------
>
>                 Key: AVRO-530
>                 URL: https://issues.apache.org/jira/browse/AVRO-530
>             Project: Avro
>          Issue Type: Improvement
>          Components: spec
>    Affects Versions: 1.3.2
>            Reporter: Jeff Hodges
>
> Suppose you have these two types in your protocol:
> {code}
> {"name": "User", "type": "record", "fields": [{"name": "current_status", "type": "Status"}]}
> {"name": "Status", "type": "record", "fields": [{"name": "author", "type": "User"}]}
> {code}
> This will raise an error! The current workaround is to define one of them at their first
usage. Like:
> {code}
> {"name": "User", "type": "record", "fields": [{"name": "current_status", "type": {"name":
"Status", "type": "record", "fields": [.. lots of fields ...]}]}
> {code}
> But this is incredibly unwieldy. It would be really nice for the spec to require all
the parsers to allow for mutual recursion, instead. It could be done by implementing a two-pass
parser. One pass to acquire names referenced, and a second to fill in those names with their
appropriate references.

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