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

["Tom White (JIRA)" <ji...@apache.org>]

Tom White created AVRO-1449:
-------------------------------

             Summary: 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


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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