Daniel Halperin created BEAM-440:
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Summary: Create.values() returns a type-unsafe Coder
Key: BEAM-440
URL: https://issues.apache.org/jira/browse/BEAM-440
Project: Beam
Issue Type: Bug
Components: sdk-java-core
Reporter: Daniel Halperin
Create.values() with no arguments will default to a VoidCoder, unless one is
set later with #setCoder(Coder).
Although it will encode its input correctly, this seems like a bad choice in
many cases. E.g., with Flatten:
PCollection<KV<SomeClass, Integer>> initial = p.apply("First",
Create.<KV<SomeClass, Integer>>of());
PCollection<KV<SomeClass, Integer>> second =
p.apply("Second", Create.of("a", "b")).apply(ParDo.of(new
MyAvroDoFn()));
PCollectionList
.of(initial).and(second)
.apply(Flatten.<KV<SomeClass, Integer>>pCollections());
This crashes trying to cast a KV from "Second" to a Void.class.
1. Suggest throwing a warning in #getDefaultOutputCoder when defaulting to
VoidCoder for an empty elements list. Should this be an error?
2. Suggest adding something like Create.empty(TypeDescriptor) to handle this
case properly.
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