I may have found a bug with accumulate and 'modify(..)' function call. It seems that once the modify(..) is called it indirectly calls AccumulateFunction.init() which invalidates accumulated data. I have included a simple test case:

import java.util.List;

import java.util.ArrayList;

declare Holder

list : List

end

rule "Hello World"

when

m : Message( )

then

insert(new Holder());

end

rule "GoodBye"

when

$holder : Holder( list == null )

$messages : List() from accumulate(

$message: Message(), collectList($message) )

then

System.out.println($messages); //<-- here the $messages list has one element

modify($holder) {

setList($messages)

}

System.out.println($messages); //<-- here the $messages list is empty

end

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Let me know if you need more information. I can create a JIRA if needed.

Thank you!

Best regards,

Michal