Github user StephanEwen commented on a diff in the pull request:
https://github.com/apache/incubator-flink/pull/203#discussion_r21740006
--- Diff: flink-java/src/main/java/org/apache/flink/api/java/DataSet.java
---
@@ -125,6 +130,11 @@ public ExecutionEnvironment getExecutionEnvironment() {
* @see TypeInformation
*/
public TypeInformation<T> getType() {
+ if (type == null) {
+ throw new InvalidTypesException("The return type could
not be determined automatically. "
--- End diff --
I think we need to be a bit better with the error message. This basically
says "didn't work, go figure it out". Directing to the log is not quite as good
as giving the right error message a the right place.
In a prior version, the code had a "MissingTypeInfo". I think that was good
because that missing type info can hold:
- The operator (name) where the return type was not determined
- And the reason for the failure (the exception from the type extractor)
Instead of directing the user to the log, we can throw an exception and in
that exception describe exactly which operation it was, what the cause was, and
we can chain the original exception.
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