[jboss-jira] [JBoss JIRA] (DROOLS-1478) Call ActivationUnMatchListener also when a rule rematches

[Geoffrey De Smet (JIRA)]

Geoffrey De Smet created DROOLS-1478:
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             Summary: Call ActivationUnMatchListener also when a rule rematches
                 Key: DROOLS-1478
                 URL: https://issues.jboss.org/browse/DROOLS-1478
             Project: Drools
          Issue Type: Enhancement
          Components: core engine
            Reporter: Geoffrey De Smet
            Assignee: Mario Fusco


ActivationUnMatchListener is part of kie-internal, so its *not public API*.

*ActivationUnMatchListener is only used by OptaPlanner* (probably):
jBPM and downstream drools module don't use it:
  https://github.com/search?q=org%3Akiegroup+ActivationUnMatchListener&type=Code
Community users probably don't use it either, because no one mentions it on StackOverflow:
  https://www.google.be/search?q=%2BActivationUnMatchListener+site:stackoverflow.com&*


The current behaviour of ActivationUnMatchListener is a pain because it doesn't unmatch if a RHS fires again, causing an imbalance. OptaPlanner works around this through a hack (that doesn't work for PLANNER-761).

For example, given this rule

{code}
global int score = 0;
rule R
when
    Wine(age < 10, $age : age)
then
    score += $age;
    addUnmatchListener(() -> score -= $age);
end
{code}

This works for a normal match and unmatch event:

{code}
Wine w = new Wine(3);
insert(w);
fireAllRules(); => score = 7;

w.age = 50;
update(w);
fireAllRules(); => unmatch triggers => score = 0; // GOOD
{code}

So events are like this:

{code}
RHS
unmatch
{code}

However if we have a rematch:
{code}
Wine w = new Wine(3);
insert(w);
fireAllRules(); => score = 7;

w.age = 4;
update(w);
fireAllRules(); => no unmatch triggers => score = 13; // should be 6!

w.age = 50;
update(w);
fireAllRules(); =>  unmatch triggers => score = 7; // should be 0!

{code}

Because the events are unbalanced:

{code}
RHS
RHS
unmatch
{code}



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