[jira] [Created] (SPARK-20143) DataType.fromJson should throw an exception with better message

["Hyukjin Kwon (JIRA)" <ji...@apache.org>]

Hyukjin Kwon created SPARK-20143:
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             Summary: DataType.fromJson should throw an exception with better message
                 Key: SPARK-20143
                 URL: https://issues.apache.org/jira/browse/SPARK-20143
             Project: Spark
          Issue Type: Improvement
          Components: SQL
    Affects Versions: 2.2.0
            Reporter: Hyukjin Kwon
            Priority: Minor


Currently, 

{code}
scala> import org.apache.spark.sql.types.DataType
import org.apache.spark.sql.types.DataType

scala> DataType.fromJson( """"abcd"""")
java.util.NoSuchElementException: key not found: abcd
  at scala.collection.MapLike$class.default(MapLike.scala:228)
  at scala.collection.AbstractMap.default(Map.scala:59)
  at scala.collection.MapLike$class.apply(MapLike.scala:141)
  at scala.collection.AbstractMap.apply(Map.scala:59)
  at org.apache.spark.sql.types.DataType$.nameToType(DataType.scala:118)
  at org.apache.spark.sql.types.DataType$.parseDataType(DataType.scala:132)
  at org.apache.spark.sql.types.DataType$.fromJson(DataType.scala:104)
  ... 48 elided

scala> DataType.fromJson( """{"abcd":"a"}""")
scala.MatchError: JObject(List((abcd,JString(a)))) (of class org.json4s.JsonAST$JObject)
  at org.apache.spark.sql.types.DataType$.parseDataType(DataType.scala:130)
  at org.apache.spark.sql.types.DataType$.fromJson(DataType.scala:104)
  ... 48 elided

scala> DataType.fromJson( """{"fields": [{"a":123}], "type": "struct"}""")
scala.MatchError: JObject(List((a,JInt(123)))) (of class org.json4s.JsonAST$JObject)
  at org.apache.spark.sql.types.DataType$.org$apache$spark$sql$types$DataType$$parseStructField(DataType.scala:169)
  at org.apache.spark.sql.types.DataType$$anonfun$parseDataType$1.apply(DataType.scala:150)
  at org.apache.spark.sql.types.DataType$$anonfun$parseDataType$1.apply(DataType.scala:150)
  at scala.collection.immutable.List.map(List.scala:273)
  at org.apache.spark.sql.types.DataType$.parseDataType(DataType.scala:150)
  at org.apache.spark.sql.types.DataType$.fromJson(DataType.scala:104)
  ... 48 elided
{code}

{{DataType.fromJson}} throws non-readable error messages for the json input. We could improve this rather than throwing {{scala.MatchError}} or {{java.util.NoSuchElementException}}.



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