Reloading a DSL-rule file doesn't clear old scheduled timers

[Flole998]

When I have a DSL-rule that does something like this:

	mytimer = createTimer(now.plusSeconds(60)) [|
		MyItem.sendCommand(ON)
		mytimer = null
	]

and the rule file is modified/reloaded after the timer has been scheduled but before it was executed there is an error thrown:

Scheduled job failed and stopped
java.lang.reflect.UndeclaredThrowableException: null
        at com.sun.proxy.$Proxy128.apply(Unknown Source) ~[?:?]
        at org.openhab.core.model.script.actions.ScriptExecution.lambda$0(ScriptExecution.java:82) ~[?:?]
        at org.openhab.core.internal.scheduler.SchedulerImpl.lambda$12(SchedulerImpl.java:184) ~[?:?]
        at org.openhab.core.internal.scheduler.SchedulerImpl.lambda$1(SchedulerImpl.java:87) ~[?:?]
        at java.util.concurrent.Executors$RunnableAdapter.call(Executors.java:515) [?:?]
        at java.util.concurrent.FutureTask.run(FutureTask.java:264) [?:?]
        at java.util.concurrent.ScheduledThreadPoolExecutor$ScheduledFutureTask.run(ScheduledThreadPoolExecutor.java:304) [?:?]
        at java.util.concurrent.ThreadPoolExecutor.runWorker(ThreadPoolExecutor.java:1128) [?:?]
        at java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:628) [?:?]
        at java.lang.Thread.run(Thread.java:829) [?:?]
Caused by: org.openhab.core.model.script.engine.ScriptExecutionException: The name '<unkown>' cannot be resolved to an item or type; line 0, column 0
        at org.openhab.core.model.script.interpreter.ScriptInterpreter.invokeFeature(ScriptInterpreter.java:141) ~[?:?]
        at org.eclipse.xtext.xbase.interpreter.impl.XbaseInterpreter._doEvaluate(XbaseInterpreter.java:1008) ~[?:?]
        at org.eclipse.xtext.xbase.interpreter.impl.XbaseInterpreter._doEvaluate(XbaseInterpreter.java:971) ~[?:?]
        at org.eclipse.xtext.xbase.interpreter.impl.XbaseInterpreter.doEvaluate(XbaseInterpreter.java:247) ~[?:?]
        at org.openhab.core.model.script.interpreter.ScriptInterpreter.doEvaluate(ScriptInterpreter.java:226) ~[?:?]
        at org.eclipse.xtext.xbase.interpreter.impl.XbaseInterpreter.internalEvaluate(XbaseInterpreter.java:227) ~[?:?]
        at org.eclipse.xtext.xbase.interpreter.impl.XbaseInterpreter._doEvaluate(XbaseInterpreter.java:874) ~[?:?]
        at org.eclipse.xtext.xbase.interpreter.impl.XbaseInterpreter.doEvaluate(XbaseInterpreter.java:243) ~[?:?]
        at org.openhab.core.model.script.interpreter.ScriptInterpreter.doEvaluate(ScriptInterpreter.java:226) ~[?:?]
        at org.eclipse.xtext.xbase.interpreter.impl.XbaseInterpreter.internalEvaluate(XbaseInterpreter.java:227) ~[?:?]
        at org.eclipse.xtext.xbase.interpreter.impl.XbaseInterpreter._doEvaluate(XbaseInterpreter.java:475) ~[?:?]
        at org.eclipse.xtext.xbase.interpreter.impl.XbaseInterpreter.doEvaluate(XbaseInterpreter.java:251) ~[?:?]
        at org.openhab.core.model.script.interpreter.ScriptInterpreter.doEvaluate(ScriptInterpreter.java:226) ~[?:?]
        at org.eclipse.xtext.xbase.interpreter.impl.XbaseInterpreter.internalEvaluate(XbaseInterpreter.java:227) ~[?:?]
        at org.eclipse.xtext.xbase.interpreter.impl.XbaseInterpreter.evaluate(XbaseInterpreter.java:213) ~[?:?]
        at org.eclipse.xtext.xbase.interpreter.impl.ClosureInvocationHandler.doInvoke(ClosureInvocationHandler.java:47) ~[?:?]
        at org.eclipse.xtext.xbase.interpreter.impl.AbstractClosureInvocationHandler.invoke(AbstractClosureInvocationHandler.java:30) ~[?:?]
        ... 10 more

I would expect that upon unloading the outstanding timers are cleared so that there is no attempt to execute them when they are gone.

[J-N-K]

There is no way for the script engine to determine what the rules does and so it can't clean up on script disposal. If #2887 is merged, you should be able to add the timers to the cache and they will be disposed.

[Flole998]

Another way to approach this would probably be an "on rulefile unloaded" trigger that is triggered whenever the rule file is unloaded, then I could add the cleanup there.

[J-N-K]

Then it's a duplicate of #2228 (when scriptLoaded is added, also scriptUnloaded should be added).

[J-N-K]

I have submitted a PR for the latter.