Script transform fails at zero records

[bamaer]

Discussed in #6866

^{Originally posted by ossDataEngineer March 24, 2026}
Hello Hop Team,

I have designed a pipeline which uses Script transform to do some processing in groovy script. The pipeline fails when the pipeline source does not send any data (i.e 0 records) with the error as below,

2026/03/24 18:40:13 - poc_no_records_script_problem - Execution started for pipeline [poc_no_records_script_problem]
2026/03/24 18:40:13 - Process data.0 - ERROR: Couldn't execute this script! Error on position --> -1:-1 :
2026/03/24 18:40:13 - Process data.0 - ERROR: org.apache.hop.core.exception.HopValueException:
2026/03/24 18:40:13 - Process data.0 - Script error:
2026/03/24 18:40:13 - Process data.0 - groovy.lang.MissingPropertyException: No such property: data for class: Script21
2026/03/24 18:40:13 - Process data.0 -
2026/03/24 18:40:13 - Process data.0 - at org.apache.hop.pipeline.transforms.script.Script.addValues(Script.java:372)
2026/03/24 18:40:13 - Process data.0 - at org.apache.hop.pipeline.transforms.script.Script.processRow(Script.java:650)
2026/03/24 18:40:13 - Process data.0 - at org.apache.hop.pipeline.transform.RunThread.run(RunThread.java:54)
2026/03/24 18:40:13 - Process data.0 - at java.base/java.lang.Thread.run(Thread.java:842)
2026/03/24 18:40:13 - Process data.0 - Caused by: javax.script.ScriptException: groovy.lang.MissingPropertyException: No such property: data for class: Script21
2026/03/24 18:40:13 - Process data.0 - at org.codehaus.groovy.jsr223.GroovyScriptEngineImpl.eval(GroovyScriptEngineImpl.java:334)
2026/03/24 18:40:13 - Process data.0 - at org.codehaus.groovy.jsr223.GroovyCompiledScript.eval(GroovyCompiledScript.java:72)
2026/03/24 18:40:13 - Process data.0 - at org.apache.hop.pipeline.transforms.script.Script.evalScript(Script.java:422)
2026/03/24 18:40:13 - Process data.0 - at org.apache.hop.pipeline.transforms.script.Script.addValues(Script.java:304)
2026/03/24 18:40:13 - Process data.0 - ... 3 more

I set the script type to 'Transform Script'. Why does the script transform execute when there is no data triggering its execution? Why can't it skip the transform execution or atleast not abort.

Not sure if this is a bug.

Thanks.

[bamaer]

.take-issue

[mattcasters]

This fix breaks 3 Script integration tests (main-0066-script.hwf) that deal with generating output without input rows.
I'll pick it up as part of the XML cleanup.