[jira] [Updated] (BEAM-440) Create.values() returns a type-unsafe Coder

["Daniel Halperin (JIRA)" <ji...@apache.org>]

     [ https://issues.apache.org/jira/browse/BEAM-440?page=com.atlassian.jira.plugin.system.issuetabpanels:all-tabpanel ]

Daniel Halperin updated BEAM-440:
---------------------------------
    Labels: newbie starter  (was: )

> 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
>              Labels: newbie, starter
>
> 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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