RuleUnit DSL does not apply RuleConfig clock type to session

[tkobayas]

Problem

When creating a RuleUnitInstance from a RuleUnitDefinition (Java DSL) with a RuleConfig that sets ClockType.PSEUDO, the pseudo clock is not applied. The session still uses the default JDKTimerService (realtime clock), causing unitInstance.getClock() to fail with a ClassCastException when cast to SessionPseudoClock.

Root Cause

In RuleUnitProviderForDSL.ModelRuleUnit.internalCreateInstance(), the RuleUnitExecutorImpl is created before the RuleConfig clock type can be merged into the session configuration:

public RuleUnitInstance<T> internalCreateInstance(T data, RuleConfig ruleConfig) {
    ReteEvaluator reteEvaluator = new RuleUnitExecutorImpl(ruleBase); // uses default REALTIME clock
    return new DSLRuleUnitInstance<>(this, data, reteEvaluator, unitGlobalsResolver, ruleConfig);
}

The DRL-based RuleUnit path handles this via RuleConfigImpl.mergeSessionConfiguration() which is called before the executor is created. The DSL path should do the same.

Expected Behavior

RuleConfig ruleConfig = RuleUnitProvider.get().newRuleConfig();
ruleConfig.setClockType(ClockType.PSEUDO);

try (RuleUnitInstance<MyUnit> unitInstance = RuleUnitProvider.get().createRuleUnitInstance(unit, ruleConfig)) {
    SessionPseudoClock clock = unitInstance.getClock(); // should work
    clock.advanceTime(40L, TimeUnit.MINUTES);
    unitInstance.fire(); // timer rules should fire after advancing
}

Actual Behavior

java.lang.ClassCastException: class org.drools.core.time.impl.JDKTimerService cannot be cast to class org.kie.api.time.SessionPseudoClock

Context

Discovered while implementing rule attribute support for RuleUnit DSL (incubator-kie#6235). The timer attribute is supported in the DSL, but cannot be fully tested with pseudo clock due to this issue.