Details
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Bug
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Status: Resolved
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Major
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Resolution: Fixed
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2.0
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None
Description
The SCXML 2 specification indicates the following in section 3.13
A transition is enabled by NULL in atomic state S if a) T lacks an 'event' attribute b) T's source state is S or an ancestor of S c) T lacks an 'cond' attribute or its 'cond' attribute evaluates to "true". (Note that such a transition can never be enabled by any named event.)
The last aspect that event-less conditions can never be triggered by a named event is currently violated by the trunk implementation.
Imagine the following example document:
<scxml xmlns="http://www.w3.org/2005/07/scxml" xmlns:rsb="http://opensource.cit-ec.de/rsb" version="1.0" initial="Start" name="CustomActionSequential"> <state id="Start"> <onentry> <log expr="'Starting onentry of state Start'"></log> <send event="'test'" delay="'100ms'"></send> <rsb:generic rsb:class="rsb.scxml.LongRunningAction" name="first"></rsb:generic> <log expr="'Finished onentry of state Start'"></log> </onentry> <onexit> <log expr="'onexit of state Start'"></log> </onexit> <transition target="End"> </transition> </state> <final id="End"> <onentry> <log expr="'onentry of state End'"></log> </onentry> </final> </scxml>
The rsb:generic action is simply a custom action that wastes some processing time by sleeping 1 second.
The logging output that you get when executing this is the following:
Aug 29, 2014 11:04:26 AM org.apache.commons.scxml2.model.Log execute INFO: null: Starting onentry of state Start Aug 29, 2014 11:04:26 AM org.apache.commons.scxml2.model.Log execute INFO: null: onexit of state Start Aug 29, 2014 11:04:26 AM org.apache.commons.scxml2.model.Log execute INFO: null: onentry of state End Aug 29, 2014 11:04:27 AM org.apache.commons.scxml2.model.Log execute INFO: null: Finished onentry of state Start
As you can see, the named event raised by the send action has triggered the transition since the outputs are not in the expected sequential order. This should not happen according to the specification.
On the other hand, if you do not send an event at all, the state machine gets stuck. This confirms that the transition was actually really triggered by the sent event. Moreover, it also sounds like a specification mismatch to me. The respective quote from the specification is:
After checking the state configuration, the Processor must select the optimal transition set enabled by NULL in the current configuration. If the set is not empty, it must execute it as a microstep.