[jira] [Resolved] (BEAM-2493) TestStream.Builder.addElements() should return the same builder

["Thomas Groh (JIRA)" <ji...@apache.org>]

     [ https://issues.apache.org/jira/browse/BEAM-2493?page=com.atlassian.jira.plugin.system.issuetabpanels:all-tabpanel ]

Thomas Groh resolved BEAM-2493.
-------------------------------
       Resolution: Not A Problem
    Fix Version/s: Not applicable

Existing PTransforms return new instances whenever their state is mutated. We decided to make the builder follow this pattern.

Changing {{TestStream}} in this way is also backwards-incompatible; instances are no longer independent when in partially constructed states.

> TestStream.Builder.addElements() should return the same builder
> ---------------------------------------------------------------
>
>                 Key: BEAM-2493
>                 URL: https://issues.apache.org/jira/browse/BEAM-2493
>             Project: Beam
>          Issue Type: Bug
>          Components: sdk-java-core
>    Affects Versions: 2.0.0
>            Reporter: Keith Berkoben
>            Assignee: Thomas Groh
>             Fix For: Not applicable
>
>
> When writing tests for pipelines, it is commonly the case where a TestStream must be built in steps ex: 
> TestStream.Builder<Object> tsb = TestStream.create(<coder>).advanceWatermarkTo(new Instant(0);
> if(<a thing is true>){
>   tsb.addElements(<element>);
> }
> TestStream<Object>  stream = tsb.advanceWatermarkToInfinity();
> The above code does not  work, however, because addElements() is creating a NEW builder rather than augmenting the existing one.  This is a-typical for a builder pattern and requires the user to do 
> tsb = tsb.addElements()
> which is more verbose and counterintuitive if one is expecting a builder. 



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