[jira] [Commented] (AVRO-1449) Check default value's type matches union at schema parse time

["Doug Cutting (JIRA)" <ji...@apache.org>]

    [ https://issues.apache.org/jira/browse/AVRO-1449?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=13886928#comment-13886928 ] 

Doug Cutting commented on AVRO-1449:
------------------------------------

Your improvements look great.  +1  I'll commit this soon unless someone objects or commits it first.

> Check default value's type matches union at schema parse time
> -------------------------------------------------------------
>
>                 Key: AVRO-1449
>                 URL: https://issues.apache.org/jira/browse/AVRO-1449
>             Project: Avro
>          Issue Type: Improvement
>          Components: java
>    Affects Versions: 1.7.6
>            Reporter: Tom White
>         Attachments: AVRO-1449.patch, AVRO-1449.patch
>
>
> A common Avro mistake is to declare optional fields as follows:
> {noformat}
> "type": ["string", "null"], "default": null
> {noformat}
> This fails at runtime since the default value's type (null) doesn't match the type of the first type in the union (string). The correct declaration is:
> {noformat}
> "type": ["null", "string"], "default": null
> {noformat}
> Doug [suggested|https://groups.google.com/a/cloudera.org/forum/#!msg/cdk-dev/Xgo5YKEcQ1Q/VkyWP2gnOEMJ] that we throw an exception at schema parse time for cases like this. To ensure backwards compatibility we could make it optional; tools could emit a warning.



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