Transition here by menu when current state is nil ->DNU

[jfabry]

I don't have code to reproduce and I don't remember how I got there, sorry

If I do a transition to with currentstate being nil then there is a DNU because anotherLRPState = nil. The problem originates in LRPInterpreter>>changeToState:withActions: because there currentstate is read.

• we should be able to reproduce and have that as a test
• the bug should be fixed

Full stack:

UndefinedObject(Object)>>doesNotUnderstand: #container
LRPInterpreter>>recursiveSetState:exitState:withActions:
LRPInterpreter>>recursiveSetState:exitState:withActions:
LRPInterpreter>>changeToState:withActions:
LRPInterpreter>>transitionTo:
[ :e | 
self code interpreter transitionTo: aState.
self highlightNode: aState name ] in LRPProgramVisualization>>elementForState: in Block: [ :e | ...
BlockClosure>>cull:
[ | selArgCount |
"show cursor in case item opens a new MVC window"
(selArgCount := selector numArgs) = 0
    ifTrue: [ target perform: selector ]
    ifFalse:
        [ selArgCount = arguments size
            ifTrue: [ target perform: selector withArguments: arguments ]
            ifFalse: [ target
                    perform: selector
                    withArguments: (arguments copyWith: evt) ] ].
self changed ] in ToggleMenuItemMorph(MenuItemMorph)>>invokeWithEvent: in Block: [ | selArgCount |...
BlockClosure>>ensure:
CursorWithMask(Cursor)>>showWhile:
ToggleMenuItemMorph(MenuItemMorph)>>invokeWithEvent:
ToggleMenuItemMorph(MenuItemMorph)>>mouseUp:
ToggleMenuItemMorph(MenuItemMorph)>>handleMouseUp:
MouseButtonEvent>>sentTo:
ToggleMenuItemMorph(Morph)>>handleEvent:
MorphicEventDispatcher>>dispatchDefault:with:
MorphicEventDispatcher>>handleMouseUp:
MouseButtonEvent>>sentTo:
[ ^ anEvent sentTo: self ] in MorphicEventDispatcher>>dispatchEvent:with: in Block: [ ^ anEvent sentTo: self ]
BlockClosure>>ensure:
MorphicEventDispatcher>>dispatchEvent:with:
ToggleMenuItemMorph(Morph)>>processEvent:using:
MorphicEventDispatcher>>dispatchDefault:with:
MorphicEventDispatcher>>handleMouseUp:
MouseButtonEvent>>sentTo:
[ ^ anEvent sentTo: self ] in MorphicEventDispatcher>>dispatchEvent:with: in Block: [ ^ anEvent sentTo: self ]
BlockClosure>>ensure:
MorphicEventDispatcher>>dispatchEvent:with:
MenuMorph(Morph)>>processEvent:using:
MenuMorph(Morph)>>processEvent:

[mcamp]

I know the problem but I cannot fully tested in Pharo5 because visualization problems. I will make a fix and let's hope it never happens again

[mcamp]

I went deeper into the code and I should reproduce it before trying to fix it

[jfabry]

Load slice 17280 from the Pharo Inbox in Pharo 5 to make the visualization work correctly. When this slice is integrated in Pharo 5 everything will work out of the box again. (see https://pharo.fogbugz.com/f/cases/17280/ )